A comprehensive evaluation of pea germplasm resources based on cluster analysis and grey relational analysis

A comprehensive evaluation of pea germplasm resources based on cluster analysis and grey relational analysis | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article A comprehensive evaluation of pea germplasm resources based on cluster analysis and grey relational analysis Tianyao Zhao, Wei Quan, Zhonghe Du, Qiang Xie, Yufan Kang, Wentong Xue This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1658053/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Pea ( Pisum sativum L.) is an economically important legume crop. Due to the growingly improved living standard and the dietary diversity, there is an increasing demand for peas and sprouts year by year, which makes it imperative to screen high-quality pea varieties. In this study, 34 pea varieties were collected for germination treatment, and their sprouting and functional characteristics were investigated. The results showed that the epicotyl length and output ratio of pea sprouts ranged from 3.54 ~ 20.66 cm and 0.91 ~ 3.03, respectively. The total phenolic content (TPC), total flavonoid content (TFC), 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radical scavenging capacity and ferric reducing antioxidant power (FRAP) varied widely, ranging from 2.33 ~ 4.61 mg GAE/g DW, 7.14 ~ 13.54 mg RUT/g DW, 46.67 ~ 65.65 µM TE/g DW and 14.95 ~ 31.26 mM Fe 2+ /g DW, respectively. Significantly high linear correlation coefficients were reported among TPC, TFC, ABTS, and FRAP of pea sprouts. Compared with ungerminated pea seeds, sprouts had richer phenolic content and superior antioxidant capacity. Principal component analysis (PCA) extracted three principal components with a total cumulative contribution rate of 84.50%. Hierarchical clustering analysis was carried out based on the extracted three principal components, and the obtained dendrogram divided pea varieties into four categories. The best-performing variety was evaluated by grey relational analysis as 9618-2, with an associate degree of 0.819. The high-quality pea varieties selected by cluster analysis and grey relational analysis were basically the same. Overall, the germinated varieties 9618-2, Dingwan 4, Dingwan 8, Baiwandou, Taiwanxiaobaihua, Chengduzhushawan, Dingwan 5, Caoyuan 224 were superior sources of natural antioxidants. Pisum sativum Sprout characteristics Phenolic content Cluster analysis Grey relational analysis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Pea is the most widely cultivated legume in temperate zones (Wille et al. 2021 ) and forms an integral part of the human diet in many countries for its abundant nutritional value. Pea is an essential source of high-quality proteins, starch, micronutrients, dietary fibers, phenolic compounds, and antioxidants (Kaur and Dhar 2019 ; Tarasevičienė et al. 2019 ; Yu et al. 2021 ). However, due to the existence of protease inhibitors such as α-amylase inhibitors, phytic acid, saponin, and other anti-nutritional factors, inappropriate intake of the pea can have adverse effects on human health, which significantly limits its application in a broader range (Boukid et al. 2021 ; Qi et al. 2021 ). Seed germination is the process for legumes to develop into new plants and enhance their nutritional value and bioavailability (Yuan et al. 2016 ; Peroxide 2020 ). Pea seeds absorb water and begin to sprout after germination, which can not only improve the nutritional diversity and reduces the anti-nutritional factors in the seeds, but also improve the absorption of proteins, vitamins, and minerals in humans. Additionally, pea sprouts have gained popularity over the years because of their short growth cycle, simple cultivation techniques, and crisp and tender taste. Of the health-improving components in pea sprouts, phenolic compounds increase and accumulate during sprouting (Balasundram 2006 ; Estrella and Lo 2006 ). These antioxidant substances are abundant in roots, stems, bark, leaves, and fruits of plants (Rauter et al. 2005 ), and they are important derivates of the pentose phosphate, shikimate, and phenylpropane pathways in plants (Baraniak 2014 ; Martínez et al. 2021 ). As essential components for plant growth and development, phenolic compounds can function as plant antitoxin, attractant of pollinators, plant pigmentation contributors, UV-resistant agents (Sampaio and Aparecida 2018 ), and reinforcing agents for the food quality (Tarasevičienė et al. 2019 ). Moreover, phenolic compounds exhibit a wide range of health protective effects, including anti-inflammatory, anti-allergic, anti-mutagenic, anti-genotoxic, and anti-cancer activities (Balasundram 2006 ; Badshah et al. 2007 ). To the best of our knowledge, previous studies on pea germplasm resources majorly focus on the agronomic trait, nutritional quality, and genetic diversity (Hou et al. 2017 ; Rana et al. 2017 ; Havananda and Luengwilai 2019 ), and reports on the selection of distinct sprout varieties and their functional qualities are scarce. Additionally, the screening methods of high-quality varieties are mainly based on the principal component analysis, cluster analysis, or gray relational analysis alone (Kaur & Dhar, 2019 ; Guibin et al., 2021). By employing cluster and grey relational analysis, this study aimed to investigate the growth traits, phenolic content, flavonoid content, and antioxidant activity of 34 peas after germination for comprehensively evaluating the market value of high-quality pea cultivars, and for providing a reference for the development and utilization of pea germplasm resources. 2. Materials And Methods 2.1 Plant Materials Pea germplasms were collected from 12 Academies of Agricultural Sciences, China, including Sichuan (SCAAS), Zhangjiakou (ZJKAAS), Qingdao (QDAAS), Xinjiang (XJAAS), Dingxi (DXAAS), Gansu (GSAAS), Qinghai (QHAAS), Beijing (CAAS), Inner Mongolia (IMAAS), Yanjiang (YJAAS), Hubei (HBAAS), Chongqing (CQAAS), and two company collections (Table 1 ). Thirty-four pea varieties were obtained, including 7 varieties each from SCAAS and QDAAS, 6 from DXAAS, 2 each from ZJKAAS, QHAAS, IMAAS, and YJAAS; 1 each from GSAAS, CAAS, HBAAS, CQAAS, and the two companies. All pea varieties were tested from one batch, which were harvested in 2018. Table 1 The name and regional distribution of pea varieties Code Variety Sample source Code Variety Sample source P1 Chengwan 268-1 SCAAS P18 Dingwan 4 DXAAS P2 Chengwan 8 P19 Dingwan 5 P3 Chengwan 10 P20 Dingwan 6 P4 Chengwan 11 P21 Dingwan 8 P5 Wuxudoujian 1 P22 9618-2 P6 Wuxudoujian 2 P23 Longwan 3 GSAAS P7 Chengduzhushawan P24 Caoyuan 28 QHAAS P8 ZDW ZJKAAS P25 Caoyuan 224 P9 Bawan 1 P26 Zhongwan 6 CAAS P10 16WDS002 QDAAS P27 Baiwandou IMAAS P11 16WDS007 P28 Qingwandou P12 16WDS010 P29 Suwan 4 YJAAS P13 16WDS017 P30 Taiwanxiaobaihua P14 16WDS018 P31 Ewan 3 HBAAS P15 16WDS021 P32 Wushanzihuawan CQAAS P16 16WDS023 P33 Xinnongcun New Rual P17 Dingwan 1 SDXAAS P34 Lvshangu Green Valley 2.2 Cultivation of pea sprouts The pea seeds with entire grains were selected and soaked for 16 hours. After the seeds were fully absorbed and expanded, the seeds of basically the same size and vigor were uniformly sowed on the seedling tray and placed in an artificial climate incubator with a temperature of 25 ± 2 ℃ and humidity of 80%. Seeds were sprouted in the dark conditions for 3 days, then the pea sprouts were incubated under light for 4 days, illuminated for 12 hours a day and watered 3 times. The pea sprouts were harvested on the 7th day of growth, and the growth index was measured. Then the fresh samples were frozen in-40 ℃ refrigerator for use. 2.3 Determination of growth index Use a ruler to measure the epicotyl length of pea sprouts, and results were expressed as cm of a sample. Use a vernier caliper to measure the stem diameter of pea sprouts, using mm as the unit of measurement. And the seed weight, fresh weight of edible parts, total weight, and root weight were weighed by an analytical balance, results were expressed as g of sample. 2.4 Extraction of phenolic compounds from pea sprouts The phenolic compounds in pea sprouts were extracted by an ultrasonic-assisted method (Shem-Tov et al. 2012 ). Pea sprouts were freeze-dried and ground into powder, passed through a 60-mesh sieve, 0.2 g sample of powder was extracted and added to 4 ml of acetone/water/acetic acid (70:29.5:0.5, v/v/v) solution, 300 W ultrasonic power was extracted for 20 min, and then centrifuged at 10000 rpm for 10 min to extract the supernatant to determine the total phenolic, total flavonoids contents, and antioxidant activity. 2.5 Determination of total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activities (AAs) of pea sprouts TPC was determined by Folin-Ciocalteu assay(Liu et al. 2016 ). The standard curve was established with gallic acid as the standard sample, and the results were expressed as mg of gallic acid equivalent per g of dry weight (mg GAE/g DW). TFC was measured using the aluminum chloride method (Paja̧k et al. 2014a ). The standard curve was expressed as mg of rutin equivalents per g of dry sample (mg RUT/g DW). The ABTS free radical scavenging capacity was determined by Wang et al.'s method (Wang et al. 2015 ). The results were expressed as µM of Trolox equivalent per g of dry sample. The ferric reducing antioxidant power (FRAP) was determined by Müller et al (Müller et al. 2011 ). The standard curve was made with FeSO 4 as the standard sample, and the results were expressed as mM Fe 2+ per g of dry sample (mM Fe 2+ /g DW). 2.6 Grey relational analysis In this study, pea sprout varieties represent a grey system, with each pea sprout variety considered as a factor in the system. TPC, TFC, ABTS free radical scavenging capacity, FRAP, total weight, edible portion fresh weight, epicotyl length, stem diameter, edible rate, water content, dry matter weight, and output ratio were correlated with growth and functional characteristics of pea sprout varieties, which was regarded as a positive correlation index. In contrast, root weight was a negative correlation index. The reference sample is an ideal variety calculated, with the best merchandise. Its positive correlation index is 5% higher than the maximum data value of the tested sample, and its negative correlation index is 5% lower than the minimum value (Hong et al. 2020 ). By calculating the weighted correlation degree between ideal varieties and tested varieties, different pea sprouts were compared. A high correlation coefficient is indicative that the degree of similarity between the sample and the ideal sample is high. The correlation coefficient was calculated according to the method reported by Kadier (Kadier et al. 2015 ). 2.7 Statistical Analysis The experiment used a randomized block design with 3 replicates for each treatment. SPSS20.0 was used for statistical data analysis, Duncan's new multiple range method was used to detect the significance of differences among different treatments, and Pearson correlation was used to detect the correlation of variables. On this basis, principal component analysis and cluster analysis were carried out. The graphing software is SigmaPlot 12.5, and each result in the figure is represented by the mean ± standard deviation. The correlation heatmap between variables was drawn using the R language. 3. Results 3.1 Screening of pea varieties with sprout characteristics Seed germination refers to the process in which the embryo breaks through the seed coat after the dry seed absorbs water and under suitable environmental conditions, completes the transition from a dormant state to a physiologically active state, and grows into an autotrophic seedling. A total of 34 pea seeds were germinated, and the growth index after harvest was shown in Fig. 1 . The results showed that the total weight of pea sprouts varied from 15.59 g to 32.96 g, among which Bawan 1 was the heaviest and Suwan 4 was the lightest. The average total weight was 23.97g, and 18 varieties were higher-than-average (Fig. 1 (a)). Pea sprouts are cotyledon-soil-retaining sprouts, and the edible part of pea sprouts is usually epicotyl, which is also the most valuable part. It was found that the edible portion fresh weight of 34 pea sprouts varied from 3.45 to 13.10 g. The heaviest and lightest varieties were 9618-2 and Suwan 4, respectively, and 16 varieties had a higher-than-average fresh weight of the edible portion of pea sprouts (7.99 g) (Fig. 1 (b)). Figure 1 (c) showed that the edible rate of pea sprouts varied from 21.66 to 46.37%, among which the varieties with the highest and the lowest edible rates were Chengduzhushawan and 16WDS007, respectively, and 14 varieties had higher-than-average edible rate (33.31%). The root weight of the 34 pea sprouts varied from 3.77 to 12.18 g. The heaviest variety was Bawan 1 and the lightest was Dingwan 6, twenty-two varieties were below the average root weight (6.48 g) (Fig. 1 (d)). The variation range of pea sprouts’ epicotyl length was 3.54 ~ 20.66 cm, among which the longest and shortest cultivars Chengduzhushawan and 16WDS007, respectively, and 14 cultivars were higher than the average epicotyl length (10.91cm) (Fig. 1 (e)). It can be seen from Fig. 1 (f) that the variation in stem diameter of pea sprouts ranged from 1.37 to 2.05 mm, with the thickest and thinnest stem varieties being Caoyuan 28 and Chengduzhushawan, respectively, and 15 varieties were wider than the average stem diameter (1.68 mm). The variation range of pea sprouts’ water content was 89.02 ~ 92.53%. The highest and lowest varieties were Dingwan 8 and 16WDS007, respectively, and 17 varieties were higher than the average water content (90.74%) (Fig. 1 (g)). Figure 1 (h) showed that the dry matter content of 34 pea sprouts varied from 7.47 to 10.98%. The highest and lowest varieties were 16WDS007 and Dingwan 8, respectively. The dry matter content of 17 varieties was higher than the average (9.26%). Output ratio is one of the critical factors for screening unique varieties of sprouts. It can be seen from Fig. 1 (i) that the variation range of pea sprouts’ output ratio was 0.91–3.03, and the greatest variety was Taiwanxiaobaihua, which was 3.32 times higher than that of Suwan 4, sixteen varieties were greater than the average output ratio (1.82). 3.2 TPC, TFC and AAs of pea sprouts To screen pea varieties with health-care functions, the TPC, TFC, and AAs of 34 pea sprouts were determined (Fig. 2 ). Figure 2 (a) showed that the TPC of pea sprouts ranged from 2.33 ~ 4.61mg GAE/g DW, with the highest and lowest content of 16WDS021 and Lvshangu, respectively. Fifteen varieties showed higher TPC than the average level (3.46 mg GAE/g DW). As shown in Fig. 2 (b), the TFC varied from 7.14 to 13.54 mg RUT/g DW among 34 pea sprouts, with Zhongwan 6 had the highest and Lvshangu had the lowest TFC, respectively. Specifically, 15 varieties were higher than the average TFC level (9.93mg RUT/g DW). It was found that the ABTS free radical scavenging capacity of pea sprouts ranged from 46.67 to 65.65 µM TE/g DW, and 16 varieties were higher than the average level (53.33 µM TE/g DW) (Fig. 2 (c). The FRAP of pea sprouts varied from 14.95 to 31.26 mM Fe 2+ /g DW, and 19 varieties were higher than the average ferrous reduction capacity (22.10 mM Fe 2+ /g DW) (Fig. 2 (d)). The varieties with the strongest and weakest antioxidant capacity were 16WDS021 and Wuxudoujian 2, respectively. In addition, compared with the pea seeds in our previous study (Zhao et al. 2020 ), TPC, TFC, and AAs of germinated pea sprouts were significantly improved (Fig. 3 ), which has the potential to be developed into functional foods, which is of great significance for promoting human health. 3.3 Correlation analysis among various indexes of pea sprouts Correlation analysis was carried out on the growth index, TPC, TFC, and AAs of 34 pea sprouts (Fig. 4 ). According to the correlation heat map, significantly high linear correlation coefficients were reported among TPC, TFC, ABTS, and FRAP of pea sprouts. The results showed that TPC was positively correlated with TFC (r 1 = 0.7563, p < 0.0001), ABTS free radical scavenging activity (r 2 = 0.6387, p < 0.0001) and FRAP (r 3 = 0.5174, p < 0.0001). In addition, TPC had a significant positive correlation with ABTS free radical scavenging activity (r = 0.711, p < 0.0001) and FRAP (r = 0.7697, p < 0.0001). However, ABTS free radical scavenging ability and FRAP also had a significant positive correlation (r = 0.7697, p < 0.0001). The correlation among the growth indexes of pea sprouts was strong. Results showed that the total weight was significantly positively correlated with the fresh weight of edible parts (r = 0.5778, p ༜0.0001) and root weight (r = 0.6940, p ༜0.0001); The fresh weight of edible parts was related to epicotyl length (r = 0.8560, p ༜0.0001), edible rate (r = 0.8187, p ༜0.0001), water content (r = 0.6593, p ༜0.0001) and stem diameter (r=-0.3714, p ༜0.0001). Root weight was negatively correlated with epicotyl length (r=-0.4577, p < 0.0001), edible rate (r=-0.5728, p < 0.0001) and positively correlated with stem diameter (r = 0.5678, p < 0.0001). Meanwhile, a significant negative correlation was reported between stem diameter and edible rate (r=-0.6435, p < 0.0001). The epicotyl length of pea sprouts had a significant negative correlation with stem diameter (r=-0.6925, p ༜0.0001) and dry matter content (r=-0.6194, p ༜0.0001), and was significantly positive correlation with the edible rate (r = 0.9443, p ༜0.0001) and water content (r = 0.6195, p ༜0.0001). The edible rate had a significant positive correlation with water content (r = 0.6420, p < 0.0001), and a significant negative correlation with dry matter content (r=-0.6420, p < 0.0001). The output ratio of pea sprouts was negatively correlated with root weight (r=-0.4262, p ༜0.0001), stem diameter (r=-0.6412, p ༜0.0001) and dry matter content (r=-0.6415, p ༜0.0001), and positively correlated with fresh weight of edible parts (r = 0.6957, p ༜0.0001), epicotyl length (r = 0.7703, p ༜0.0001) and edible rate (r = 0.8784, p ༜0.0001). In addition, there were also significant correlations between phenolic contents, antioxidant activities, and growth indicators. The pea sprouts with higher stem diameter and dry matter content had richer TPC, TFC, and stronger AAs. 3.4 Principal component analysis (PCA) of the variables of pea sprouts Based on the significant correlation among the variables of pea sprouts, PCA was conducted to investigate the impact of individual traits. The chi-square test showed that the significance level was 0.000 (less than 0.01), which indicated that each index had a high correlation and was suitable for PCA analysis. It was found that the total variance contribution rate of the three principal component factors reached 84.50%. Among them, the variance contribution rates of principal component 1 (PC1), principal component 2 (PC2), and principal component 3 (PC3) were 54.98%, 17.06%, and 12.46%, respectively, and the eigenvalues were 7.15, 2.22, and 1.62, respectively (Table 2 ). Table 2 Contribution percentage and major characters associated with the first three principal components of 34 pea varieties and their eigenvectors X loadings PC1 PC2 PC3 Explained proportion of variation (%) 54.98 17.06 12.46 Cumulative proportion of variation (%) 54.98 72.04 84.5 Traits Eigenvectors X1 -0.127 0.84 0.115 X2 -0.202 0.912 0.161 X3 -0.248 0.852 -0.059 X4 -0.459 0.75 0.088 X5 0.301 -0.004 0.92 X6 0.891 -0.24 0.271 X7 -0.3 0.176 0.872 X8 0.83 -0.422 -0.164 X9 -0.437 0.533 0.528 X10 0.884 -0.299 -0.284 X11 0.835 -0.311 0.076 X12 -0.835 0.31 -0.076 X13 0.884 -0.013 -0.242 In each extracted principal component, there were some traits make a significant contribution. Among them, PC1 mainly reflected the sprouting characteristics of pea sprouts, in which the fresh weight of edible parts, epicotyl length, edible rate, water content, dry matter content, and output ratio had higher loads, which could be used as important reference indicators; PC2 embodied the nutritional and health care function of sprouts. The traits with the positive and high load in the eigenvector included TPC, TFC, ABTS free radical scavenging power, and FRAP; total weight and root weight played a major role in PC3 (Table 2 ). 3.5 Clustering analysis The phenotypic traits of 34 pea sprouts were clustered using the phylogenetic clustering method, and the classification distance ranged from 0 to 25. Figure 5 showed that the tree diagram of the system divided all pea sprouts into four groups. Among them, Suwan 4 was the first group, and its sprouts had poor growth, low phenolic content, and weak antioxidant capacity. The second group included three pea sprouts: ZDW, Qingwandou, and Bawan 1, which root weights were the heaviest among the 34 pea sprouts. The third group consists of 9 pea sprouts with thicker stems and higher TFC: 16WDS018, 16WDS021, Caoyuan 28, Zhongwan 6, 16WDS002, Longwan 3, 16WDS007, 16WDS017, and Chengwan 268-1. The remaining 21 pea sprouts were classified into the fourth group, most of which were varieties with better growth and sprouting characteristics. 3.6 Comprehensive value evaluation of pea sprouts In order to objectively evaluate the sprout characteristics and functional quality of pea sprouts and screen out the best pea sprouts varieties, the grey relational analysis was used to assess the comprehensive value of 34 pea sprouts (Table S1). The results showed that the cultivar significantly affected the sprout and functional properties of pea sprouts. The heat map of the influence of each factor on the final result in the grey theory system explained the differences among the varieties of pea sprouts, and more directly reflected the contribution of each index to the final result, which was helpful to explain the difference between the weighted correlation degree of the samples. The heat map for 9618-2 possessed the largest number of green blocks, mainly including TFC, fresh weight of edible part, epicotyl length, edible rate, water content, and output ratio, which indicated that the above indexes of this variety were closer to the ideal variety, that is the main reason why this variety ranked in the forefront. However, Ewan 3 showed more orange and red blocks, with the lowest hierarchy (Fig. 6 ). The ranking of all pea sprout varieties was shown in Table 3 . Generally speaking, 9618-2 (0.819) was the closest pea sprout variety to the ideal sample, followed by Dingwan 4 (0.815), Dingwan 8 (0.805), Baiwandou (0.797), and Taiwanxiaobaihua (0.797). Table 3 The gray relational grade values of 34 pea sprouts Code Variety WGRD Code Variety WGRD 1 9618-2 0.819 18 Dingwan 1 0.751 2 Dingwan 4 0.815 19 16WDS017 0.751 3 Dingwan 8 0.805 20 Chengwan 11 0.750 4 Baiwandou 0.797 21 16WDS007 0.749 5 Taiwanxiaobaihua 0.797 22 Chengwan 10 0.748 6 Chengduzhushawan 0.795 23 Wuxudoujian 1 0.746 7 Dingwan 5 0.793 24 Lvshangu 0.745 8 16WDS021 0.791 25 Chengwan 8 0.745 9 Caoyuan 224 0.778 26 Longwan 3 0.744 10 Caoyuan 28 0.775 27 ZDW 0.740 11 Chengwan 268-1 0.772 28 Wushanzihuawan 0.739 12 Zhongwan 6 0.768 29 Qingwandou 0.739 13 Dingwan 6 0.765 30 16WDS023 0.735 14 Xinnongcun 0.764 31 Bawan 1 0.734 15 16WDS018 0.763 32 16WDS010 0.724 16 16WDS002 0.754 33 Suwan 4 0.718 17 Wuxudoujian 2 0.752 34 Ewan 3 0.715 4 Discussion Seed germination is the essential link in the plant life cycle, which determines the growth and yield of plants (Podlesna et al. 2015 ). Cellular respiration, protein synthesis, and other physiological and biochemical reactions are started after seeds absorb water (Kılınçer and Demir 2019 ). Epicotyl length and stem diameter are important morphological indexes of sprouts, edible portion fresh weight, edible rate, and output ratio are the main indexes to measure the economic benefits of sprouts, which influence and interact with each other. It was found that the superior pea varieties for sprouting were Wuxudoujian 1, Wuxudoujian 2, Chengduzhushawan, Dingwan 1, Dingwan 2, Dingwan 4, Dingwan 5, Dingwan 6, Dingwan 8, 9618-2, Caoyuan 224, Baiwandou, Taiwanxiaobaihua, Xinnongcun, and Lvshangu. Genetic variation-driven differences might account for the wide variation range of pea sprout growth traits. Pea sprouts with sprouting properties presented a better performance in the cell division between stems, hypocotyl growth, photosynthetic efficiency, and high yield, which can be considered a remarkable variety for the family cultivation and food industry. It is necessary to evaluate agronomic traits such as seed yield, stress resistance, disease resistance, sensory evaluation, and market demand for large-scale production. Seed germination is a simple, low-cost, and high-benefit method that not only reduces the levels of anti-nutritional and anti-digestive factors, but also induces the accumulation of secondary metabolites, such as phenolic compounds (Tarasevičienė et al. 2019 ). It was found that the total phenolic contents of lentils reached 379 mg GAE/100 g DW on the 8th day of germination (Aguilera et al. 2014 ). The total phenolic contents of kidney bean and pea reached the maximum value on the 6th and 7th day of germination (685.2 mg EAG/100 g; 910.6mg EAG/100 g ) (Martínez et al. 2021 ). The total flavonoid contents of mung bean and black bean after germination were 5.58 mg RE/g FW and 4.25 mg RE/g FW, respectively (Xue et al. 2016 ). Besides, our results showed that the total phenolic and flavonoid contents of 34 pea sprouts ranged from 2.33 to 4.61 mg GAE/DW and 7.14 to 13.54 mg RUT/DW, respectively. The main reason for this phenomenon could be attributed to differences in species, varieties, germination conditions, growth environment, the extraction method of phenolic substances, and standard samples used. Overall, a higher content of total phenolic and total flavonoids of 34 pea sprouts indicated a more robust antioxidant activity. Similar findings were also reported in studies of germinated lentils (Tarasevičienė et al. 2019 ) and mung beans (Paja̧k et al. 2014b ). The varieties with higher phenolic contents and stronger antioxidant activities are valuable sources of natural antioxidants. Compared to seeds, the total phenolic contents of cowpea, jack bean, dolichos, and mucuna significantly increased after germination (Aguilera et al. 2013 ), and the total flavonoid level of mung bean sprouts increased almost 3 times compared to that of mung bean seeds (Paja̧k et al. 2014b ). Estrella and Lo (Estrella and Lo 2006 ) reported that the antioxidant activities of peas and kidney beans were significantly enhanced after germination, which was consistent with our results. During the germination of legume seeds, the types and activity of enzymes increased, which accelerated the hydrolysis reaction and promoted the synthesis of secondary metabolites (Xue et al. 2016 ). Meanwhile, with the enhancement of respiration in the later germination stage, more reactive oxygen species and hydroxyl radicals would be synthesized in sprouts, promoting membrane lipid peroxidation and thereby increasing the phenolic types and contents. With the rapid development of science and technology, the demand for varieties in modern agriculture tends to the comprehensive requirements for multiple traits. In this study, pea varieties were quickly divided into four categories by cluster analysis, among which the third and fourth categories performed better. Meanwhile, combined with the objective and accurate grey relational analysis method, differences of the varieties were evaluated, and the high-quality pea varieties that were suitable for widespread planting and market promotion with functional characteristics were screened out. The screening and evaluation results of excellent varieties by the two analysis methods were basically the same, which was consistent with the results on cowpea (Fu et al. 2022 ). In general, 9618-2, Dingwan 4, Dingwan 8, Baiwandou, Taiwanxiaobaihua, Chengduzhushawan, Dingwan 5, Caoyuan 224 were the high-quality varieties with comprehensive performance. Our results provided an excellent theoretical foundation for the breeding, developing, and utilizing of pea varieties. 5 Conclusion Through cluster analysis and grey relational analysis, the high-quality pea varieties with sprout and functional characteristics were comprehensively selected: 9618-2, Dingwan 4, Dingwan 8, Baiwandou, Taiwanxiaobaihua, Chengduzhushawan, Dingwan 5, Caoyuan 224. These germinated sprouts are essential sources of natural antioxidants and can be used as raw materials and dietary supplements for functional products. Declarations Acknowledgments The authors appreciate the 12 Academies of Agriculture Sciences and two companies for providing valuable pea varieties. Funding China Agriculture Research System of MOF and MARA- Food Legumes (CARS-08) Conflict of interest The authors declare no conflict of interest. References Aguilera Y, Díaz MF, Jiménez T et al (2013) Changes in nonnutritional factors and antioxidant activity during germination of nonconventional legumes. J Agric Food Chem 61:8120–8125 Aguilera Y, Liébana R, Herrera T et al (2014) Effect of illumination on the content of melatonin, phenolic compounds, and antioxidant activity during germination of lentils ( Lens culinaris L.) and kidney beans ( Phaseolus vulgaris L.). J Agric Food Chem 62:10736–10743 Badshah A, Zeb A, Bibi N, Akbar S (2007) Influence of germination techniques on phytic acid and polyphenols content of chickpea ( Cicer arietinum L.) sprouts. 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Guangdong Agric Sci 49:24–36 (In Chinese) Havananda T, Luengwilai K (2019) Variation in floral antioxidant activities and phytochemical properties among butterfly pea ( Clitoria ternatea L.) germplasm. Genet Resour Crop Evol 66:645–658 Hong J, Mu T, Sun H et al (2020) Valorization of the green waste parts from sweet potato ( Impoea batatas L.): Nutritional, phytochemical composition, and bioactivity evaluation. Food Sci Nutr 8:4086–4097 Hou WH, Wang JL, Dan B, Hu D (2017) Analysis of protein content and genetic diversity in pea germplasm in Tibet. Asian Agric Reaserch 9:62–69 Huang GB, Guan YB, Niu YQ et al (2021) Evaluation and selection of pea varieties based on grey correlation analysis. Ningxia J Agric For Sci Technol 62:1–5 (In Chinese) Kadier A, Abdeshahian P, Simayi Y et al (2015) Grey relational analysis for comparative assessment of different cathode materials in microbial electrolysis cells. Energy 90:1556–1562 Kaur V, Dhar S (2019) Genetic diversity assessment in garden pea ( Pisum sativum L.) germplasm through principal component analysis. Int J Chem Stud 7:482–486 Kılınçer FN, Demir MK (2019) Physical and chemical properties of germinated some cereals and legumes. Gida / J Food 44:419–429 Liu HK, Chen YY, Hu TT et al (2016) The influence of light-emitting diodes on the phenolic compounds and antioxidant activities in pea sprouts. J Funct Foods 25:459–465 Martínez B, Moguel R, Jim C et al (2021) Anti-inflammatory properties of phenolic extracts from Phaseolus vulgaris and Pisum sativum during germination. Food Biosci 42:101067 Müller L, Fröhlich K, Böhm V (2011) Comparative antioxidant activities of carotenoids measured by ferric reducing antioxidant power (FRAP), ABTS bleaching assay (αTEAC), DPPH assay and peroxyl radical scavenging assay. Food Chem 129:139–148 Paja̧k P, Socha R, Gałkowska D et al (2014a) Phenolic profile and antioxidant activity in selected seeds and sprouts. Food Chem 143:300–306 Paja̧k P, Socha R, Gałkowska D et al (2014b) Phenolic profile and antioxidant activity in selected seeds and sprouts. Food Chem 143:300–306 Peroxide H (2020) Improving polyphenolic compounds: antioxidant activity in chickpea sprouts through elicitation with hydrogen peroxide. Foods 9:1–15 Podlesna A, Gładyszewska B, Podlesny J, Zgrajka W (2015) Changes in the germination process and growth of pea in effect of laser seed irradiation. Int Agrophysics 29:485–492 Qi MM, Zhang GY, Ren ZS et al (2021) Impact of extrusion temperature on in vitro digestibility and pasting properties of pea flour. Plant Foods Hum Nutr 76:26–30 Rana JC, Rana M, Sharma V et al (2017) Genetic diversity and structure of pea (Pisum sativum L.) germplasm based on morphological and SSR markers. Plant Mol Biol Report 35:118–129 Rauter AP, Martins A, Borges C et al (2005) Liquid chromatography-diode array detection-electrospray ionisation mass spectrometry/nuclear magnetic resonance analyses of the anti-hyperglycemic flavonoid extract of genista tenera: structure elucidation of a flavonoid-C-glycoside. J Chromatogr A 1089:59–64 Sampaio GR, Aparecida R (2018) Identification and quantification of phenolic compounds and antioxidant activity in cowpeas of brs xiquexique cultivar. Univ Fed Rural do Semi-Árido 2125:209–216 Shem-Tov Y, Badani H, Segev A et al (2012) Determination of total polyphenol, flavonoid and anthocyanin contents and antioxidant capacities Of skins from peanut ( Arachis Hypogaea ) lines with different skin colors. J Food Biochem 36:301–308 Tarasevičienė Ž, Viršilė A, Danilčenko H et al (2019) Effects of germination time on the antioxidant properties of edible seeds. CyTA - J Food 17:447–454 Wang X, Xie K, Zhuang HN et al (2015) Volatile flavor compounds, total polyphenolic contents and antioxidant activities of a China gingko wine. Food Chem 182:41–46 Wille L, Kurmann M, Messmer MM, Studer B (2021) Untangling the pea root rot complex reveals microbial markers for plant health. Front Plant Sci 12:1–12 Xue ZH, Wang C, Zhai LJ et al (2016) Bioactive compounds and antioxidant activity of mung bean ( Vigna radiata L.), soybean ( Glycine max L.) and black bean ( Phaseolus vulgaris L.) during the germination process. Czech J Food Sci 34:68–78 Yu BY, Xiang DQ, Mahfuz H et al (2021) Understanding starch metabolism in pea seeds towards tailoring functionality for value-added utilization. Int J Mol Sci 22:8972 Yuan LY, Wu J, Wang CG et al (2016) Effect of zinc enrichment on growth and nutritional quality in pea sprouts. J Food Nutr Res 4:100–107 Zhao TY, Su WJ, Qin Y et al (2020) Phenotypic diversity of pea ( Pisum sativum L.) varieties and the polyphenols, flavonoids, and antioxidant activity of their seeds. Ciência Rural 50:1–16 Supplementary Files TableS1.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Major revisions 07 Jul, 2022 Reviewers agreed at journal 01 Jun, 2022 Reviewers invited by journal 29 May, 2022 Editor assigned by journal 17 May, 2022 First submitted to journal 15 May, 2022 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-1658053","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":109595825,"identity":"8cc3cd28-ae9c-4970-920e-346ef5c67ff0","order_by":0,"name":"Tianyao Zhao","email":"","orcid":"","institution":"China Agricultural University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Tianyao","middleName":"","lastName":"Zhao","suffix":""},{"id":109595826,"identity":"e26bc90d-2c67-4e74-b30f-b2eca8535d10","order_by":1,"name":"Wei Quan","email":"","orcid":"","institution":"China Agricultural University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Quan","suffix":""},{"id":109595827,"identity":"4a99de7d-ad67-4c60-8652-db2088623495","order_by":2,"name":"Zhonghe Du","email":"","orcid":"","institution":"China Agricultural University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhonghe","middleName":"","lastName":"Du","suffix":""},{"id":109595828,"identity":"3c30db3c-c856-4f35-94f5-e094b4ce2217","order_by":3,"name":"Qiang Xie","email":"","orcid":"","institution":"China Agricultural University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Qiang","middleName":"","lastName":"Xie","suffix":""},{"id":109595829,"identity":"fc8f4f82-c922-49c9-b6a8-bc7dc8852990","order_by":4,"name":"Yufan Kang","email":"","orcid":"","institution":"China Agricultural University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yufan","middleName":"","lastName":"Kang","suffix":""},{"id":109595830,"identity":"4c0cbe63-a4fa-431d-9de4-1f4580642560","order_by":5,"name":"Wentong Xue","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAo0lEQVRIiWNgGAWjYHACxgcQOoFoHczMBiRrYZMgTYvBjfxjFT9qDjPws+cYMPzcQYQWyRnJbDd7jh1mkOx5Y8DYe4YILfzSyWy3GdgOA63LMWBmbCNCCxtQSzHDv8MM9kRrAdkCVAm0RYJYLZLzHxtL9val80iceVZwsJcYLQZnDj788OObtRx/e/LGBz+J0QIDPCDiAAkaRsEoGAWjYBTgAwDqBC+mRQLfcgAAAABJRU5ErkJggg==","orcid":"","institution":"China Agricultural University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Wentong","middleName":"","lastName":"Xue","suffix":""}],"badges":[],"createdAt":"2022-05-15 10:24:54","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1658053/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1658053/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":22089293,"identity":"7542ac3f-ae4c-4f74-9391-2ef531552e5b","added_by":"auto","created_at":"2022-05-31 17:07:14","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1020691,"visible":true,"origin":"","legend":"\u003cp\u003eGrowth indexes of 34 pea sprouts\u003c/p\u003e\u003cp\u003eNote: (a)total weight; (b) edible portion fresh weight; (c) edible rate; (d) root weight; (e) epicotyl length; (f) stem diameter; (g) water content; (h) dry matter content; (i) output ratio.\u003c/p\u003e","description":"","filename":"Fig1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-1658053/v1/964e01718bd603137d8f4df2.jpeg"},{"id":22089645,"identity":"d00bfd88-aa58-4974-ae0a-71f1c4b13d3b","added_by":"auto","created_at":"2022-05-31 17:12:13","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":126978,"visible":true,"origin":"","legend":"\u003cp\u003eTotal phenolic content\u003cstrong\u003e (a)\u003c/strong\u003e, total flavonoid content \u003cstrong\u003e(b)\u003c/strong\u003e, ABTS free radical scavenging \u003cstrong\u003e(c)\u003c/strong\u003e, and ferric reducing antioxidant power \u003cstrong\u003e(d)\u003c/strong\u003e of pea sprouts\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-1658053/v1/8bda5e76674155655d55f979.png"},{"id":22089646,"identity":"c31426c0-79dd-4fd8-b96b-9fb4e5b39059","added_by":"auto","created_at":"2022-05-31 17:12:13","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":195081,"visible":true,"origin":"","legend":"\u003cp\u003eRelative growth rates of TPC, TFC, ABTS, and FRAP in pea sprouts compared with their seeds\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-1658053/v1/91aeeefb39f47a4810b75983.png"},{"id":22089289,"identity":"11eeba5a-4527-490f-9180-4c5ba9cece8d","added_by":"auto","created_at":"2022-05-31 17:07:13","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":32953,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation analysis of variables of pea sprout\u003cstrong\u003e \u003c/strong\u003e\u003c/p\u003e\u003cp\u003eNote: X1: Total phenolic content, mg GAE/g DW); X2: Total flavonoid content, mg RUT/g DW); X3: ABTS free radical scavenging activity, µM TE/g DW; X4: Ferric reducing antioxidant power, mM Fe\u003csup\u003e2+\u003c/sup\u003e/g DW; X5: Total weight, g; X6: Edible portion fresh weight, g; X7: Root weight, g; X8: Epicotyl length, cm; X9: Stem diameter, mm; X10: Edible rate, %; X11: Water content, %; X12: Dry matter content, %. X13：Output ratio. Blue represents positive correlation, and red represents negative correlation. The darker the color, the larger the square, and the stronger the correlation. The same is below.\u003c/p\u003e","description":"","filename":"Fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-1658053/v1/5b6202ba8d8f81389d38fcf3.png"},{"id":22089287,"identity":"f456da6d-6063-45ee-87f0-5e7fe34c75f6","added_by":"auto","created_at":"2022-05-31 17:07:13","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":127661,"visible":true,"origin":"","legend":"\u003cp\u003eHierarchical cluster analysis of 34 pea collections based on three extracted principal components\u003c/p\u003e","description":"","filename":"Fig5.png","url":"https://assets-eu.researchsquare.com/files/rs-1658053/v1/5620061dee102db7b2bca635.png"},{"id":22089291,"identity":"78d57c1b-4988-4588-8831-bdf1b31136e1","added_by":"auto","created_at":"2022-05-31 17:07:14","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1927411,"visible":true,"origin":"","legend":"\u003cp\u003eThe weighted gray relational grades (WGRG) heat map of 34 pea sprout varieties\u003c/p\u003e\u003cp\u003eNote: The color scale from red to green indicates the change of the index value from small to large.\u003c/p\u003e","description":"","filename":"Fig6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-1658053/v1/c9d80a6e0dd5dfff453b4fc2.jpeg"},{"id":22089648,"identity":"980fab79-b820-438f-8589-da563f5f2789","added_by":"auto","created_at":"2022-05-31 17:12:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":952956,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1658053/v1/12ff568a-0c44-4596-bd19-51923795a74e.pdf"},{"id":22089647,"identity":"444db489-ef6f-4ede-b022-1efdfbc2e987","added_by":"auto","created_at":"2022-05-31 17:12:14","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":25202,"visible":true,"origin":"","legend":"","description":"","filename":"TableS1.docx","url":"https://assets-eu.researchsquare.com/files/rs-1658053/v1/c0e3023656bc2e2aea155e03.docx"}],"financialInterests":"","formattedTitle":"A comprehensive evaluation of pea germplasm resources based on cluster analysis and grey relational analysis","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePea is the most widely cultivated legume in temperate zones (Wille et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and forms an integral part of the human diet in many countries for its abundant nutritional value. Pea is an essential source of high-quality proteins, starch, micronutrients, dietary fibers, phenolic compounds, and antioxidants (Kaur and Dhar \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Tarasevičienė et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Yu et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). However, due to the existence of protease inhibitors such as α-amylase inhibitors, phytic acid, saponin, and other anti-nutritional factors, inappropriate intake of the pea can have adverse effects on human health, which significantly limits its application in a broader range (Boukid et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Qi et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSeed germination is the process for legumes to develop into new plants and enhance their nutritional value and bioavailability (Yuan et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Peroxide \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Pea seeds absorb water and begin to sprout after germination, which can not only improve the nutritional diversity and reduces the anti-nutritional factors in the seeds, but also improve the absorption of proteins, vitamins, and minerals in humans. Additionally, pea sprouts have gained popularity over the years because of their short growth cycle, simple cultivation techniques, and crisp and tender taste. Of the health-improving components in pea sprouts, phenolic compounds increase and accumulate during sprouting (Balasundram \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Estrella and Lo \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). These antioxidant substances are abundant in roots, stems, bark, leaves, and fruits of plants (Rauter et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2005\u003c/span\u003e), and they are important derivates of the pentose phosphate, shikimate, and phenylpropane pathways in plants (Baraniak \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Mart\u0026iacute;nez et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). As essential components for plant growth and development, phenolic compounds can function as plant antitoxin, attractant of pollinators, plant pigmentation contributors, UV-resistant agents (Sampaio and Aparecida \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), and reinforcing agents for the food quality (Tarasevičienė et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Moreover, phenolic compounds exhibit a wide range of health protective effects, including anti-inflammatory, anti-allergic, anti-mutagenic, anti-genotoxic, and anti-cancer activities (Balasundram \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Badshah et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2007\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo the best of our knowledge, previous studies on pea germplasm resources majorly focus on the agronomic trait, nutritional quality, and genetic diversity (Hou et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Rana et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Havananda and Luengwilai \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), and reports on the selection of distinct sprout varieties and their functional qualities are scarce. Additionally, the screening methods of high-quality varieties are mainly based on the principal component analysis, cluster analysis, or gray relational analysis alone (Kaur \u0026amp; Dhar, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Guibin et al., 2021). By employing cluster and grey relational analysis, this study aimed to investigate the growth traits, phenolic content, flavonoid content, and antioxidant activity of 34 peas after germination for comprehensively evaluating the market value of high-quality pea cultivars, and for providing a reference for the development and utilization of pea germplasm resources.\u003c/p\u003e"},{"header":"2. Materials And Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Plant Materials\u003c/h2\u003e \u003cp\u003ePea germplasms were collected from 12 Academies of Agricultural Sciences, China, including Sichuan (SCAAS), Zhangjiakou (ZJKAAS), Qingdao (QDAAS), Xinjiang (XJAAS), Dingxi (DXAAS), Gansu (GSAAS), Qinghai (QHAAS), Beijing (CAAS), Inner Mongolia (IMAAS), Yanjiang (YJAAS), Hubei (HBAAS), Chongqing (CQAAS), and two company collections (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Thirty-four pea varieties were obtained, including 7 varieties each from SCAAS and QDAAS, 6 from DXAAS, 2 each from ZJKAAS, QHAAS, IMAAS, and YJAAS; 1 each from GSAAS, CAAS, HBAAS, CQAAS, and the two companies. All pea varieties were tested from one batch, which were harvested in 2018.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe name and regional distribution of pea varieties\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCode\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVariety\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSample source\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCode\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eVariety\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eSample source\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChengwan 268-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"6\" rowspan=\"7\"\u003e \u003cp\u003eSCAAS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDingwan 4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003eDXAAS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChengwan 8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDingwan 5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChengwan 10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDingwan 6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChengwan 11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDingwan 8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWuxudoujian 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9618-2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWuxudoujian 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLongwan 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eGSAAS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChengduzhushawan\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCaoyuan 28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eQHAAS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eZDW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eZJKAAS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCaoyuan 224\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBawan 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eZhongwan 6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCAAS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16WDS002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"6\" rowspan=\"7\"\u003e \u003cp\u003eQDAAS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eBaiwandou\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eIMAAS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16WDS007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eQingwandou\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16WDS010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSuwan 4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eYJAAS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16WDS017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTaiwanxiaobaihua\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16WDS018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEwan 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eHBAAS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16WDS021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eWushanzihuawan\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCQAAS\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16WDS023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eXinnongcun\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNew Rual\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDingwan 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSDXAAS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLvshangu\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eGreen Valley\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Cultivation of pea sprouts\u003c/h2\u003e \u003cp\u003eThe pea seeds with entire grains were selected and soaked for 16 hours. After the seeds were fully absorbed and expanded, the seeds of basically the same size and vigor were uniformly sowed on the seedling tray and placed in an artificial climate incubator with a temperature of 25\u0026thinsp;\u0026plusmn;\u0026thinsp;2 ℃ and humidity of 80%. Seeds were sprouted in the dark conditions for 3 days, then the pea sprouts were incubated under light for 4 days, illuminated for 12 hours a day and watered 3 times. The pea sprouts were harvested on the 7th day of growth, and the growth index was measured. Then the fresh samples were frozen in-40 ℃ refrigerator for use.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Determination of growth index\u003c/h2\u003e \u003cp\u003eUse a ruler to measure the epicotyl length of pea sprouts, and results were expressed as cm of a sample. Use a vernier caliper to measure the stem diameter of pea sprouts, using mm as the unit of measurement. And the seed weight, fresh weight of edible parts, total weight, and root weight were weighed by an analytical balance, results were expressed as g of sample.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Extraction of phenolic compounds from pea sprouts\u003c/h2\u003e \u003cp\u003eThe phenolic compounds in pea sprouts were extracted by an ultrasonic-assisted method (Shem-Tov et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Pea sprouts were freeze-dried and ground into powder, passed through a 60-mesh sieve, 0.2 g sample of powder was extracted and added to 4 ml of acetone/water/acetic acid (70:29.5:0.5, v/v/v) solution, 300 W ultrasonic power was extracted for 20 min, and then centrifuged at 10000 rpm for 10 min to extract the supernatant to determine the total phenolic, total flavonoids contents, and antioxidant activity.\u003c/p\u003e \u003cp\u003e2.5 Determination of total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activities (AAs) of pea sprouts\u003c/p\u003e \u003cp\u003eTPC was determined by Folin-Ciocalteu assay(Liu et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The standard curve was established with gallic acid as the standard sample, and the results were expressed as mg of gallic acid equivalent per g of dry weight (mg GAE/g DW). TFC was measured using the aluminum chloride method (Paja̧k et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2014a\u003c/span\u003e). The standard curve was expressed as mg of rutin equivalents per g of dry sample (mg RUT/g DW).\u003c/p\u003e \u003cp\u003eThe ABTS free radical scavenging capacity was determined by Wang et al.'s method (Wang et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The results were expressed as \u0026micro;M of Trolox equivalent per g of dry sample. The ferric reducing antioxidant power (FRAP) was determined by M\u0026uuml;ller et al (M\u0026uuml;ller et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). The standard curve was made with FeSO\u003csub\u003e4\u003c/sub\u003e as the standard sample, and the results were expressed as mM Fe\u003csup\u003e2+\u003c/sup\u003e per g of dry sample (mM Fe\u003csup\u003e2+\u003c/sup\u003e/g DW).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Grey relational analysis\u003c/h2\u003e \u003cp\u003eIn this study, pea sprout varieties represent a grey system, with each pea sprout variety considered as a factor in the system. TPC, TFC, ABTS free radical scavenging capacity, FRAP, total weight, edible portion fresh weight, epicotyl length, stem diameter, edible rate, water content, dry matter weight, and output ratio were correlated with growth and functional characteristics of pea sprout varieties, which was regarded as a positive correlation index. In contrast, root weight was a negative correlation index. The reference sample is an ideal variety calculated, with the best merchandise. Its positive correlation index is 5% higher than the maximum data value of the tested sample, and its negative correlation index is 5% lower than the minimum value (Hong et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). By calculating the weighted correlation degree between ideal varieties and tested varieties, different pea sprouts were compared. A high correlation coefficient is indicative that the degree of similarity between the sample and the ideal sample is high. The correlation coefficient was calculated according to the method reported by Kadier (Kadier et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.7 Statistical Analysis\u003c/h2\u003e \u003cp\u003eThe experiment used a randomized block design with 3 replicates for each treatment. SPSS20.0 was used for statistical data analysis, Duncan's new multiple range method was used to detect the significance of differences among different treatments, and Pearson correlation was used to detect the correlation of variables. On this basis, principal component analysis and cluster analysis were carried out. The graphing software is SigmaPlot 12.5, and each result in the figure is represented by the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. The correlation heatmap between variables was drawn using the R language.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Screening of pea varieties with sprout characteristics\u003c/h2\u003e \u003cp\u003eSeed germination refers to the process in which the embryo breaks through the seed coat after the dry seed absorbs water and under suitable environmental conditions, completes the transition from a dormant state to a physiologically active state, and grows into an autotrophic seedling. A total of 34 pea seeds were germinated, and the growth index after harvest was shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The results showed that the total weight of pea sprouts varied from 15.59 g to 32.96 g, among which Bawan 1 was the heaviest and Suwan 4 was the lightest. The average total weight was 23.97g, and 18 varieties were higher-than-average (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a)). Pea sprouts are cotyledon-soil-retaining sprouts, and the edible part of pea sprouts is usually epicotyl, which is also the most valuable part. It was found that the edible portion fresh weight of 34 pea sprouts varied from 3.45 to 13.10 g. The heaviest and lightest varieties were 9618-2 and Suwan 4, respectively, and 16 varieties had a higher-than-average fresh weight of the edible portion of pea sprouts (7.99 g) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b)). Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e (c) showed that the edible rate of pea sprouts varied from 21.66 to 46.37%, among which the varieties with the highest and the lowest edible rates were Chengduzhushawan and 16WDS007, respectively, and 14 varieties had higher-than-average edible rate (33.31%). The root weight of the 34 pea sprouts varied from 3.77 to 12.18 g. The heaviest variety was Bawan 1 and the lightest was Dingwan 6, twenty-two varieties were below the average root weight (6.48 g) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(d)). The variation range of pea sprouts\u0026rsquo; epicotyl length was 3.54\u0026thinsp;~\u0026thinsp;20.66 cm, among which the longest and shortest cultivars Chengduzhushawan and 16WDS007, respectively, and 14 cultivars were higher than the average epicotyl length (10.91cm) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e (e)). It can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(f) that the variation in stem diameter of pea sprouts ranged from 1.37 to 2.05 mm, with the thickest and thinnest stem varieties being Caoyuan 28 and Chengduzhushawan, respectively, and 15 varieties were wider than the average stem diameter (1.68 mm). The variation range of pea sprouts\u0026rsquo; water content was 89.02\u0026thinsp;~\u0026thinsp;92.53%. The highest and lowest varieties were Dingwan 8 and 16WDS007, respectively, and 17 varieties were higher than the average water content (90.74%) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(g)). Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e (h) showed that the dry matter content of 34 pea sprouts varied from 7.47 to 10.98%. The highest and lowest varieties were 16WDS007 and Dingwan 8, respectively. The dry matter content of 17 varieties was higher than the average (9.26%). Output ratio is one of the critical factors for screening unique varieties of sprouts. It can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e (i) that the variation range of pea sprouts\u0026rsquo; output ratio was 0.91\u0026ndash;3.03, and the greatest variety was Taiwanxiaobaihua, which was 3.32 times higher than that of Suwan 4, sixteen varieties were greater than the average output ratio (1.82).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.2 TPC, TFC and AAs of pea sprouts\u003c/h2\u003e \u003cp\u003eTo screen pea varieties with health-care functions, the TPC, TFC, and AAs of 34 pea sprouts were determined (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (a) showed that the TPC of pea sprouts ranged from 2.33\u0026thinsp;~\u0026thinsp;4.61mg GAE/g DW, with the highest and lowest content of 16WDS021 and Lvshangu, respectively. Fifteen varieties showed higher TPC than the average level (3.46 mg GAE/g DW). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b), the TFC varied from 7.14 to 13.54 mg RUT/g DW among 34 pea sprouts, with Zhongwan 6 had the highest and Lvshangu had the lowest TFC, respectively. Specifically, 15 varieties were higher than the average TFC level (9.93mg RUT/g DW). It was found that the ABTS free radical scavenging capacity of pea sprouts ranged from 46.67 to 65.65 \u0026micro;M TE/g DW, and 16 varieties were higher than the average level (53.33 \u0026micro;M TE/g DW) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(c). The FRAP of pea sprouts varied from 14.95 to 31.26 mM Fe\u003csup\u003e2+\u003c/sup\u003e/g DW, and 19 varieties were higher than the average ferrous reduction capacity (22.10 mM Fe\u003csup\u003e2+\u003c/sup\u003e/g DW) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (d)). The varieties with the strongest and weakest antioxidant capacity were 16WDS021 and Wuxudoujian 2, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn addition, compared with the pea seeds in our previous study (Zhao et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), TPC, TFC, and AAs of germinated pea sprouts were significantly improved (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), which has the potential to be developed into functional foods, which is of great significance for promoting human health.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Correlation analysis among various indexes of pea sprouts\u003c/h2\u003e \u003cp\u003eCorrelation analysis was carried out on the growth index, TPC, TFC, and AAs of 34 pea sprouts (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). According to the correlation heat map, significantly high linear correlation coefficients were reported among TPC, TFC, ABTS, and FRAP of pea sprouts. The results showed that TPC was positively correlated with TFC (r\u003csub\u003e1\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.7563, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), ABTS free radical scavenging activity (r\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.6387, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) and FRAP (r\u003csub\u003e3\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.5174, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). In addition, TPC had a significant positive correlation with ABTS free radical scavenging activity (r\u0026thinsp;=\u0026thinsp;0.711, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) and FRAP (r\u0026thinsp;=\u0026thinsp;0.7697, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). However, ABTS free radical scavenging ability and FRAP also had a significant positive correlation (r\u0026thinsp;=\u0026thinsp;0.7697, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001).\u003c/p\u003e \u003cp\u003eThe correlation among the growth indexes of pea sprouts was strong. Results showed that the total weight was significantly positively correlated with the fresh weight of edible parts (r\u0026thinsp;=\u0026thinsp;0.5778, \u003cem\u003ep\u003c/em\u003e༜0.0001) and root weight (r\u0026thinsp;=\u0026thinsp;0.6940, \u003cem\u003ep\u003c/em\u003e༜0.0001); The fresh weight of edible parts was related to epicotyl length (r\u0026thinsp;=\u0026thinsp;0.8560, \u003cem\u003ep\u003c/em\u003e༜0.0001), edible rate (r\u0026thinsp;=\u0026thinsp;0.8187, \u003cem\u003ep\u003c/em\u003e༜0.0001), water content (r\u0026thinsp;=\u0026thinsp;0.6593, \u003cem\u003ep\u003c/em\u003e༜0.0001) and stem diameter (r=-0.3714, \u003cem\u003ep\u003c/em\u003e༜0.0001). Root weight was negatively correlated with epicotyl length (r=-0.4577, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), edible rate (r=-0.5728, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001) and positively correlated with stem diameter (r\u0026thinsp;=\u0026thinsp;0.5678, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). Meanwhile, a significant negative correlation was reported between stem diameter and edible rate (r=-0.6435, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). The epicotyl length of pea sprouts had a significant negative correlation with stem diameter (r=-0.6925, \u003cem\u003ep\u003c/em\u003e༜0.0001) and dry matter content (r=-0.6194, \u003cem\u003ep\u003c/em\u003e༜0.0001), and was significantly positive correlation with the edible rate (r\u0026thinsp;=\u0026thinsp;0.9443, \u003cem\u003ep\u003c/em\u003e༜0.0001) and water content (r\u0026thinsp;=\u0026thinsp;0.6195, \u003cem\u003ep\u003c/em\u003e༜0.0001). The edible rate had a significant positive correlation with water content (r\u0026thinsp;=\u0026thinsp;0.6420, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), and a significant negative correlation with dry matter content (r=-0.6420, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). The output ratio of pea sprouts was negatively correlated with root weight (r=-0.4262, \u003cem\u003ep\u003c/em\u003e༜0.0001), stem diameter (r=-0.6412, \u003cem\u003ep\u003c/em\u003e༜0.0001) and dry matter content (r=-0.6415, \u003cem\u003ep\u003c/em\u003e༜0.0001), and positively correlated with fresh weight of edible parts (r\u0026thinsp;=\u0026thinsp;0.6957, \u003cem\u003ep\u003c/em\u003e༜0.0001), epicotyl length (r\u0026thinsp;=\u0026thinsp;0.7703, \u003cem\u003ep\u003c/em\u003e༜0.0001) and edible rate (r\u0026thinsp;=\u0026thinsp;0.8784, \u003cem\u003ep\u003c/em\u003e༜0.0001).\u003c/p\u003e \u003cp\u003eIn addition, there were also significant correlations between phenolic contents, antioxidant activities, and growth indicators. The pea sprouts with higher stem diameter and dry matter content had richer TPC, TFC, and stronger AAs.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Principal component analysis (PCA) of the variables of pea sprouts\u003c/h2\u003e \u003cp\u003eBased on the significant correlation among the variables of pea sprouts, PCA was conducted to investigate the impact of individual traits. The chi-square test showed that the significance level was 0.000 (less than 0.01), which indicated that each index had a high correlation and was suitable for PCA analysis. It was found that the total variance contribution rate of the three principal component factors reached 84.50%. Among them, the variance contribution rates of principal component 1 (PC1), principal component 2 (PC2), and principal component 3 (PC3) were 54.98%, 17.06%, and 12.46%, respectively, and the eigenvalues were 7.15, 2.22, and 1.62, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eContribution percentage and major characters associated with the first three principal components of 34 pea varieties and their eigenvectors\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX loadings\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePC1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePC2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePC3\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExplained proportion of variation (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e54.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12.46\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCumulative proportion of variation (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e54.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e72.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e84.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTraits\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eEigenvectors\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.127\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.115\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.202\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.912\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.161\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.248\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.852\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.059\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.459\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.088\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.301\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.92\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.891\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.271\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.176\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.872\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.422\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.164\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.437\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.533\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.528\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.884\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.299\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.284\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.835\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.311\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.076\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-0.835\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.076\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eX13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.884\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.242\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\u003cp\u003eIn each extracted principal component, there were some traits make a significant contribution. Among them, PC1 mainly reflected the sprouting characteristics of pea sprouts, in which the fresh weight of edible parts, epicotyl length, edible rate, water content, dry matter content, and output ratio had higher loads, which could be used as important reference indicators; PC2 embodied the nutritional and health care function of sprouts. The traits with the positive and high load in the eigenvector included TPC, TFC, ABTS free radical scavenging power, and FRAP; total weight and root weight played a major role in PC3 (Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Clustering analysis\u003c/h2\u003e \u003cp\u003eThe phenotypic traits of 34 pea sprouts were clustered using the phylogenetic clustering method, and the classification distance ranged from 0 to 25. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e showed that the tree diagram of the system divided all pea sprouts into four groups. Among them, Suwan 4 was the first group, and its sprouts had poor growth, low phenolic content, and weak antioxidant capacity. The second group included three pea sprouts: ZDW, Qingwandou, and Bawan 1, which root weights were the heaviest among the 34 pea sprouts. The third group consists of 9 pea sprouts with thicker stems and higher TFC: 16WDS018, 16WDS021, Caoyuan 28, Zhongwan 6, 16WDS002, Longwan 3, 16WDS007, 16WDS017, and Chengwan 268-1. The remaining 21 pea sprouts were classified into the fourth group, most of which were varieties with better growth and sprouting characteristics.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Comprehensive value evaluation of pea sprouts\u003c/h2\u003e \u003cp\u003eIn order to objectively evaluate the sprout characteristics and functional quality of pea sprouts and screen out the best pea sprouts varieties, the grey relational analysis was used to assess the comprehensive value of 34 pea sprouts (Table S1). The results showed that the cultivar significantly affected the sprout and functional properties of pea sprouts.\u003c/p\u003e \u003cp\u003eThe heat map of the influence of each factor on the final result in the grey theory system explained the differences among the varieties of pea sprouts, and more directly reflected the contribution of each index to the final result, which was helpful to explain the difference between the weighted correlation degree of the samples. The heat map for 9618-2 possessed the largest number of green blocks, mainly including TFC, fresh weight of edible part, epicotyl length, edible rate, water content, and output ratio, which indicated that the above indexes of this variety were closer to the ideal variety, that is the main reason why this variety ranked in the forefront. However, Ewan 3 showed more orange and red blocks, with the lowest hierarchy (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The ranking of all pea sprout varieties was shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Generally speaking, 9618-2 (0.819) was the closest pea sprout variety to the ideal sample, followed by Dingwan 4 (0.815), Dingwan 8 (0.805), Baiwandou (0.797), and Taiwanxiaobaihua (0.797).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe gray relational grade values of 34 pea sprouts\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCode\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVariety\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWGRD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCode\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eVariety\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eWGRD\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9618-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.819\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDingwan 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.751\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDingwan 4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.815\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e16WDS017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.751\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDingwan 8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.805\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eChengwan 11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.750\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBaiwandou\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.797\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e16WDS007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.749\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTaiwanxiaobaihua\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.797\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eChengwan 10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.748\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChengduzhushawan\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.795\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eWuxudoujian 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.746\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDingwan 5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.793\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLvshangu\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.745\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16WDS021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.791\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eChengwan 8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.745\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCaoyuan 224\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.778\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLongwan 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.744\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCaoyuan 28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.775\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eZDW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.740\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChengwan 268-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.772\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eWushanzihuawan\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.739\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eZhongwan 6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.768\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eQingwandou\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.739\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDingwan 6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.765\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e16WDS023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.735\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eXinnongcun\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.764\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eBawan 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.734\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16WDS018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.763\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e16WDS010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.724\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16WDS002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.754\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSuwan 4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.718\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWuxudoujian 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.752\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEwan 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.715\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cp\u003eSeed germination is the essential link in the plant life cycle, which determines the growth and yield of plants (Podlesna et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Cellular respiration, protein synthesis, and other physiological and biochemical reactions are started after seeds absorb water (Kılın\u0026ccedil;er and Demir \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Epicotyl length and stem diameter are important morphological indexes of sprouts, edible portion fresh weight, edible rate, and output ratio are the main indexes to measure the economic benefits of sprouts, which influence and interact with each other. It was found that the superior pea varieties for sprouting were Wuxudoujian 1, Wuxudoujian 2, Chengduzhushawan, Dingwan 1, Dingwan 2, Dingwan 4, Dingwan 5, Dingwan 6, Dingwan 8, 9618-2, Caoyuan 224, Baiwandou, Taiwanxiaobaihua, Xinnongcun, and Lvshangu. Genetic variation-driven differences might account for the wide variation range of pea sprout growth traits. Pea sprouts with sprouting properties presented a better performance in the cell division between stems, hypocotyl growth, photosynthetic efficiency, and high yield, which can be considered a remarkable variety for the family cultivation and food industry. It is necessary to evaluate agronomic traits such as seed yield, stress resistance, disease resistance, sensory evaluation, and market demand for large-scale production.\u003c/p\u003e \u003cp\u003eSeed germination is a simple, low-cost, and high-benefit method that not only reduces the levels of anti-nutritional and anti-digestive factors, but also induces the accumulation of secondary metabolites, such as phenolic compounds (Tarasevičienė et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). It was found that the total phenolic contents of lentils reached 379 mg GAE/100 g DW on the 8th day of germination (Aguilera et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). The total phenolic contents of kidney bean and pea reached the maximum value on the 6th and 7th day of germination (685.2 mg EAG/100 g; 910.6mg EAG/100 g ) (Mart\u0026iacute;nez et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The total flavonoid contents of mung bean and black bean after germination were 5.58 mg RE/g FW and 4.25 mg RE/g FW, respectively (Xue et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Besides, our results showed that the total phenolic and flavonoid contents of 34 pea sprouts ranged from 2.33 to 4.61 mg GAE/DW and 7.14 to 13.54 mg RUT/DW, respectively.\u003c/p\u003e \u003cp\u003eThe main reason for this phenomenon could be attributed to differences in species, varieties, germination conditions, growth environment, the extraction method of phenolic substances, and standard samples used. Overall, a higher content of total phenolic and total flavonoids of 34 pea sprouts indicated a more robust antioxidant activity. Similar findings were also reported in studies of germinated lentils (Tarasevičienė et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) and mung beans (Paja̧k et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2014b\u003c/span\u003e). The varieties with higher phenolic contents and stronger antioxidant activities are valuable sources of natural antioxidants.\u003c/p\u003e \u003cp\u003eCompared to seeds, the total phenolic contents of cowpea, jack bean, dolichos, and mucuna significantly increased after germination (Aguilera et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), and the total flavonoid level of mung bean sprouts increased almost 3 times compared to that of mung bean seeds (Paja̧k et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2014b\u003c/span\u003e). Estrella and Lo (Estrella and Lo \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) reported that the antioxidant activities of peas and kidney beans were significantly enhanced after germination, which was consistent with our results. During the germination of legume seeds, the types and activity of enzymes increased, which accelerated the hydrolysis reaction and promoted the synthesis of secondary metabolites (Xue et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Meanwhile, with the enhancement of respiration in the later germination stage, more reactive oxygen species and hydroxyl radicals would be synthesized in sprouts, promoting membrane lipid peroxidation and thereby increasing the phenolic types and contents.\u003c/p\u003e \u003cp\u003eWith the rapid development of science and technology, the demand for varieties in modern agriculture tends to the comprehensive requirements for multiple traits. In this study, pea varieties were quickly divided into four categories by cluster analysis, among which the third and fourth categories performed better. Meanwhile, combined with the objective and accurate grey relational analysis method, differences of the varieties were evaluated, and the high-quality pea varieties that were suitable for widespread planting and market promotion with functional characteristics were screened out. The screening and evaluation results of excellent varieties by the two analysis methods were basically the same, which was consistent with the results on cowpea (Fu et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In general, 9618-2, Dingwan 4, Dingwan 8, Baiwandou, Taiwanxiaobaihua, Chengduzhushawan, Dingwan 5, Caoyuan 224 were the high-quality varieties with comprehensive performance. Our results provided an excellent theoretical foundation for the breeding, developing, and utilizing of pea varieties.\u003c/p\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eThrough cluster analysis and grey relational analysis, the high-quality pea varieties with sprout and functional characteristics were comprehensively selected: 9618-2, Dingwan 4, Dingwan 8, Baiwandou, Taiwanxiaobaihua, Chengduzhushawan, Dingwan 5, Caoyuan 224. These germinated sprouts are essential sources of natural antioxidants and can be used as raw materials and dietary supplements for functional products.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments \u0026nbsp;\u0026nbsp;\u003c/strong\u003eThe authors appreciate the 12 Academies of Agriculture Sciences and two companies for providing valuable pea varieties.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding \u0026nbsp;\u0026nbsp;\u003c/strong\u003eChina Agriculture Research System of MOF and MARA- Food Legumes (CARS-08)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest \u0026nbsp;\u0026nbsp;\u003c/strong\u003eThe authors declare no conflict of interest.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAguilera Y, D\u0026iacute;az MF, Jim\u0026eacute;nez T et al (2013) Changes in nonnutritional factors and antioxidant activity during germination of nonconventional legumes. 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Ci\u0026ecirc;ncia Rural 50:1\u0026ndash;16\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"genetic-resources-and-crop-evolution","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"gres","sideBox":"Learn more about [Genetic Resources and Crop Evolution](https://www.springer.com/journal/10722)","snPcode":"10722","submissionUrl":"https://submission.nature.com/new-submission/10722/3","title":"Genetic Resources and Crop Evolution","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Pisum sativum, Sprout characteristics, Phenolic content, Cluster analysis, Grey relational analysis","lastPublishedDoi":"10.21203/rs.3.rs-1658053/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1658053/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePea (\u003cem\u003ePisum sativum\u003c/em\u003e L.) is an economically important legume crop. Due to the growingly improved living standard and the dietary diversity, there is an increasing demand for peas and sprouts year by year, which makes it imperative to screen high-quality pea varieties. In this study, 34 pea varieties were collected for germination treatment, and their sprouting and functional characteristics were investigated. The results showed that the epicotyl length and output ratio of pea sprouts ranged from 3.54\u0026thinsp;~\u0026thinsp;20.66 cm and 0.91\u0026thinsp;~\u0026thinsp;3.03, respectively. The total phenolic content (TPC), total flavonoid content (TFC), 2,2\u0026rsquo;-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radical scavenging capacity and ferric reducing antioxidant power (FRAP) varied widely, ranging from 2.33\u0026thinsp;~\u0026thinsp;4.61 mg GAE/g DW, 7.14\u0026thinsp;~\u0026thinsp;13.54 mg RUT/g DW, 46.67\u0026thinsp;~\u0026thinsp;65.65 \u0026micro;M TE/g DW and 14.95\u0026thinsp;~\u0026thinsp;31.26 mM Fe\u003csup\u003e2+\u003c/sup\u003e/g DW, respectively. Significantly high linear correlation coefficients were reported among TPC, TFC, ABTS, and FRAP of pea sprouts. Compared with ungerminated pea seeds, sprouts had richer phenolic content and superior antioxidant capacity. Principal component analysis (PCA) extracted three principal components with a total cumulative contribution rate of 84.50%. Hierarchical clustering analysis was carried out based on the extracted three principal components, and the obtained dendrogram divided pea varieties into four categories. The best-performing variety was evaluated by grey relational analysis as 9618-2, with an associate degree of 0.819. The high-quality pea varieties selected by cluster analysis and grey relational analysis were basically the same. Overall, the germinated varieties 9618-2, Dingwan 4, Dingwan 8, Baiwandou, Taiwanxiaobaihua, Chengduzhushawan, Dingwan 5, Caoyuan 224 were superior sources of natural antioxidants.\u003c/p\u003e","manuscriptTitle":"A comprehensive evaluation of pea germplasm resources based on cluster analysis and grey relational analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-05-31 17:07:11","doi":"10.21203/rs.3.rs-1658053/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revisions","date":"2022-07-07T13:25:44+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2022-06-01T06:17:05+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2022-05-29T18:09:35+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2022-05-17T05:16:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"Genetic Resources and Crop Evolution","date":"2022-05-15T06:23:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"genetic-resources-and-crop-evolution","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"gres","sideBox":"Learn more about [Genetic Resources and Crop Evolution](https://www.springer.com/journal/10722)","snPcode":"10722","submissionUrl":"https://submission.nature.com/new-submission/10722/3","title":"Genetic Resources and Crop Evolution","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"2db08e29-ef58-4a49-a3db-3a6d6bd3fab5","owner":[],"postedDate":"May 31st, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2022-10-29T08:19:06+00:00","versionOfRecord":[],"versionCreatedAt":"2022-05-31 17:07:11","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-1658053","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1658053","identity":"rs-1658053","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}