Effect of leaf extracts on fruiting and sporulation of Cronartium pini and C. ribicola on susceptible alternate hosts

Effect of leaf extracts on fruiting and sporulation of Cronartium pini and C. ribicola on susceptible alternate hosts | 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 Effect of leaf extracts on fruiting and sporulation of Cronartium pini and C. ribicola on susceptible alternate hosts Juha Piispanen, Ulrich Bergmann, Jouni Karhu, Tuomas Kauppila, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8191801/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Resistance of plants to rust fungi may depend on the chemical quality of plants, suggesting that leaf extracts from resistant plant species could be useful in development of bio-based solutions against rust diseases. Pine trees ( Pinus spp.) are affected by Cronartium rusts ( C. pini , C. ribicola ). In their life cycle, these rusts infect alternate host plants, some of which are more rust resistant than others. We sprayed leaf extracts from resistant alternate host ( Melampyrum pratense , Impatiens glandulifera , Veronica chamaedrys , Ribes rubrum ) and tested—both in the laboratory and on live plants—whether those extracts reduce rust spore production on plants that are normally easy to infect ( Melampyrum sylvaticum , Impatiens balsamina , Paeonia lactiflora , Ribes nigrum ). Two commercial compounds, previously linked to rust resistance of alternate hosts to Cronartium rusts, a methanol control and an untreated control were also included to the experiment. Formation of rust uredinia and telia were estimated on the leaves after 6 weeks of incubation. In the laboratory, uredinia and telia of C. pini developed most abundantly on Paeonia lactiflora . Coverage of uredinia and telia did not differ between extracts on the leaves, but coverages of uredinia were significantly higher compared to dry control in the laboratory. In the greenhouse, infection percentage of leaves with uredinia and telia differed significantly among plant species but the treatments with extracts did not result in significant differences in infection percentage of the test plants. The results indicated that none of the tested extracts from rust-resistant alternate hosts and commercial compounds significantly inhibited fruiting and sporulation of Cronartium spp. on susceptible alternate hosts at medium (100 ppm) concentration. Alternate hosts Leaf extracts Rust resistance Scots pine blister rust White-pine blister rust Introduction Cronartium pini (Willd.) Jørst. is a pathogen that kills pine ( Pinus spp.) trees in Europe and Asia (Gäumann, 1959 ; CABI, 2020 ). The rust is also a quarantine species in North America (Kim et al., 2022 ). In the 2000s, C. pini caused severe losses on young Pinus sylvestris L. plantations in northern Europe, especially in nutrient-rich soils (Kaitera, 2000 ; Wulff et al., 2012 ), although the rust was previously known especially as a disease of mature pines on poor sites (Kaitera et al., 1994 ). Another Cronartium, C. ribicola Fisch., is a serious pathogen of five-needle pines especially in North America (Zambino, 2010 ). Cronartium pini spreads via alternate hosts of over 50 susceptible species in 14 plant families (Kaitera et al., 2015 ; Kim et al., 2022 ). The most important alternate host species belong to hemiparasites in Orobanchaceae (Kaitera, 1999 ; Kaitera et al., 1999 , 2012 , 2015 , 2017 , 2018 ; Kaitera & Nuorteva, 2003a , b ). In genus Melampyrum , M. sylvaticum L., M. nemorosum L., M. arvense L. and M. cristatum L. are highly susceptible, while M. pratense shows resistance against C. pini (Kaitera, 1999 ; Kaitera et al., 2015 ). Cronartium ribicola spreads via plants in genus Ribes (Grossulariaceae). In Finland, most R. nigrum cultivars are susceptible, while R. rubrum cultivars show resistance against C. ribicola (Kaitera & Nuorteva, 2006 ). Recent studies have shown that chemical composition of P. sylvestris wood changes after C. pini infection (Kaitera et al., 2021 ), suggesting that terpenes and resin acids are produced by the host as defensive chemicals against Cronartium . Terpenes have been linked to C. ribicola resistance in Pinus also earlier (Michelozzi et al., 1991 ; Bullington et al., 2018 ) and also phenolic compounds have been assigned defensive roles in pine resistance against Cronartium rusts (Boyer, 1964 ; Hanover & Hoff, 1966 ; Hudgins et al., 2005 ; Sniezko et al., 2014 ). The possible role of phenolics in alternate host resistance against Cronartium has also been studied, in both the susceptible and resistant species (e.g., Piispanen et al., 2023 ). It has been suggested that variation in rust resistance between the closely related species such as M. sylvaticum and M. pratense may be due to variation in leaf phenolic chemistry (Kaitera & Witzell, 2016 ). Polyphenolics, such as luteolin and apigenin flavonoids with documented antimicrobial impact on bacterial, viral and fungal pathogens (Cushnie & Lamb, 2005 ) occur at high concentrations in some Melampyrum species (Naumov et al., 1998 ). Recently, chlorogenic acid (Kaitera & Witzell, 2016 ; Piispanen et al., 2023 ) and quercitrin (Piispanen et al., 2023 ) were found to be enriched in C. pini -resistant M. pratense . With tightening regulations on environmentally harmful synthetic fungicides, there is an urgent demand for bio-based, sustainable methods to manage tree diseases both in nurseries and in the field. The aim of this study was to explore whether extracts from alternate hosts could be useful as bio-based suppressants against Cronartium . Therefore, we conducted in vivo and in vitro studies to investigate the effect of leaf extracts from selected resistant alternate hosts of C. pini and C. ribicola on the fruiting and sporulation of Cronartium species. We hypothesized that the externally added extracts from resistant alternative host species could suppress the fruiting and sporulation of Cronartium rusts on the susceptible hosts. Material and methods Plant material for extracts Plant species resistant to C. pini , i.e., M. pratense (65°2,69N, 25°28,04E), Impatiens glandulifera Royle (65°3,86N, 25°27,79E) and Veronica chamaedrys L. (65°1,30N, 25°25,96E), were from natural habitats in the city area of Oulu in northern Finland, while species resistant to C. ribicola were commercial seedlings of Ribes rubrum L. from a commercial nursery (Särkän taimitarha). Plants were collected and transported to the laboratory, where their healthy leaves were detached, air-dried and used for preparation of leaf extracts. Plant material for inoculations For the laboratory experiment, healthy leaves of susceptible M. sylvaticum were collected from the city area of Oulu in early July 2021. In addition, leaves of commercial plants of susceptible R. nigrum and Paeonia lactiflora Pall from the nursery (Särkän taimitarha), and Impatiens balsamina L. grown from seeds in the Botanical Gardens of Oulu University in May 2021, were used in the laboratory experiments. Whole plants of the above mentioned R. nigrum , P. lactiflora and I. balsamina were also used in the greenhouse experiment. Preparation of plant extracts In the laboratory, healthy green leaves of the rust-resistant plants were separated from the rest of the plant material aseptically with sterile tweezers. The leaves were air-dried for about a week in the laminar cabin in open paper bags and stored at -20°C prior to extraction. The leaf samples were crushed manually inside a paper bag until a powdery consistency was achieved. Of each sample,1 g was extracted in 40 mL methanol (HPLC grade, Merck, 1.06007.2500)(for the extraction, see Piispanen et al., 2023 ). The extracts were kept at + 4 ºC for 24 hours and diluted to 100 mL by sterile water. In addition, solutions of commercial compounds, potentially linked to resistance of Cronartium rusts based on the results of earlier studies (Kaitera & Witzell, 2016 ; Piispanen et al., 2023 ), were also tested: chlorogenic acid (Acros Organics, 109.240.010) and quercitrin (Cayman Chemical Company, CAYM19866), 5 g each, were dissolved to 100 ml of sterile water: methanol (40:60 v/v). The further diluted solutions for the experiments were made daily from these base solutions (100 ppm for plant extracts and 0,5 ppm for chlorogenic acid and quercitrin). The methanol-water control solutions contained same amount of methanol than the plant extracts used in the experiments. Inoculum and inoculation treatments Aeciospores of C. pini were collected from Kolari (67º9,64N, 23º40,06E), northern Finland, in mid-June (June 13) 2021. The collection site was a P. sylvestris stand where the presence and pathogenicity of the rust had been confirmed (Kaitera et al., 2015 ). Five branches bearing C. pini lesions were cut and transported to the Lynet laboratory of the Natural Resources Institute Finland in Oulu. Aeciospores were released into sterile Petri dishes by cutting the surface of aecia aseptically in a laminar cabin using a scalpel. Aeciospores of C. ribicola were then dusted from Pinus cembra L. directly to Petri dishes in the field by cutting the surface of aecia from four lesions in Oulunsalo (64º56,50N, 25º22,60E) in late May (May 28) 2021. The aeciospores of both species were stored at 5°C before usage. Germination of the spores was measured by dusting spores on 1.5% water agar, incubating the plates at 21.5°C in the daylight for 24 h, and counting germination from 10 microscopic areas on agar using a light microscope (Mx4300H, Meiji Techno Co., LTD). Mean germination of C. pini was 94% (87–98%) and of C. ribicola 85% (81–91%). Laboratory ( in vitro ) experiment Five Petri dishes were prepared with two leaves of each susceptible alternate host ( R. nigrum, M. sylvaticum , P. lactiflora , and I. balsamina and) per plate floating on sterilized water in the laboratory experiment. Prior to inoculation, leaves were treated with extracts (one extract per plate). Four extracts were from M. pratense , I. glandulifera , V. chamaedrys and R. rubrum , and chlorogenic acid and quercitrin were used as additional commercial compounds. Two controls were included: methanol-water (40:60, v/v) and dry leaves without methanol or water. The plant extracts were used at 100 ppm and commercial compounds at concentration of 0.5 ppm. The leaves were soaked in extracts, solutions or pure water:methanol for 5 sec, except for the dry control. After treatments, aeciospores of C. pini were dusted using an artist’s pencil on leaves of M. sylvaticum , P. lactiflora and I. balsamina , while C. ribicola was dusted on R. nigrum . Plates without inoculation were included to control for natural infections on the leaves. The plates were incubated for 6 weeks at 18°C in the dark in a growth chamber (KB240, Binder GmbH, Tuttlingen, Germany). After the incubations, the leaves were checked using a stereomicroscope (M5A, Wild Heerbrugg, Switzerland) to determine the coverage of uredinia and telia per leaf using classes ‘0%’, ‘1–20%’, ’21–40%’, ’41–60%’, ’61–80%’, ’81–99%’ and ‘100%’. Later, the mean percentages of these classes were used in the calculations. Greenhouse ( in vivo ) experiment In the greenhouse, eight plants per species were prepared for the experiment. All leaves of P. lactiflora and I. balsamina , and leaves from one branch of R. nigrum per plant, were sprayed with six extracts and two controls. One extract or control was sprayed per plant. The extracts were the same as in the laboratory experiment. As controls, a methanol:water (40:60, v/v) treatment and a water treatment were used. The sprayed leaves of P. lactiflora and I. balsamina plants were thereafter dusted with C. pini and those of R. nigrum with C. ribicola aeciospores with an artist’s pencil. After inoculation, the plants were covered with a plastic bag for 48 h to promote spore germination. After 6 weeks of incubation, the leaves were collected and the numbers of leaves carrying uredinia or telia were counted using a stereomicroscope in the laboratory (see above). The infection percentage was used to indicate the success of infection. Statistical analysis The effect of extract treatment, plant species and their interaction on coverage of uredinia and telia was modelled using ANOVA of SAS (SAS Institute Inc., version 9.4). The data from the laboratory experiment (6 week’s inoculation) was subjected to one-way analysis of variance with the GLM procedure and the Tukey’s Studentized Range (HSD) post hoc test to test. For the data from the greenhouse experiment, infection percentage of leaves (%) was compared separately between plant species and treatments using also one-way analysis of variance and Tukey’s (HSD) test. Results Cronartium fruiting and sporulation in vitro In vitro inoculations were successful, resulting in mean uredinia coverage values ranging from 5% ( C. pini on M. sylvaticum ) to ca. 70% ( C. ribicola on R. nigrum ), and mean telia coverage values ranging from ca. 6% ( C. pini on M. sylvaticum ) to 35% ( C. pini on P. lactiflora ) (Table 1 ). Natural infections were not found on the uninoculated leaves. Table 1 Mean coverage (x) and standard deviation (std) of uredinia and telia on detached leaf after inoculation with Cronartium pini on Melampyrum sylvaticum , Paeonia lactiflora and Impatiens balsamina , and C. ribicola on Ribes nigrum in the laboratory after 6-weeks of incubation (n = 90 per plant species). Different letters after mean values indicate significant difference (Tukey’s HSD) at p < 0.001. Plant species Fruiting stages Uredinia Telia x std min max x std min max Ribes nigrum 69.60 a 33.91 0 100.0 9.08 a 11.69 0 70.5 Melampyrum sylvaticum 5.42 c 11.50 0 50.5 5.65 a 13.29 0 50.5 Paeonia lactiflora 36.05 b 35.96 0 100.0 34.51 b 36.35 0 100.0 Impatiens balsamina 6.63 c 13.45 0 70.5 6.12 a 13.47 0 70.5 Significant differences occurred between plant species in the mean coverage of uredinia (ANOVA, F 3,356 =205.53, p < 0.001) and telia (F 3,356 =48.14, p < 0.001) after six weeks of incubation time (Table 2 ). In pairwise comparisons, significant differences in coverage of uredinia were found between all species except between M. sylvaticum and I. balsamina (Tukey’s HSD, Table 1 ). The coverage of telia differed significantly only between P. lactiflora and the other three species (Table 1 ). Table 2 ANOVA table on the effect of plant extract treatments on uredinia and telia formation after inoculation of leaves of four test plants ( R. nigrum , M. sylvaticum , P. laciflora and I. balsamina ) with Cronartium pini or C. ribicola after incubation of six weeks in the laboratory. Uredinia Telia Source Type III SS DF MS F P Type III SS DF MS F P Corrected 361619 35 10332 25.46 p < 0.001 97147 35 2776 7.73 p < 0.001 Intercept 311729 1 311729 768.07 p < 0.01 68959 1 68959 192.00 p < 0.001 Species 247816 3 82605 203.53 p < 0.001 51869 3 17290 48.14 p < 0.001 Treatment 48896 8 6112 15.06 p < 0.001 16553 8 2069 5.76 p < 0.001 Species x Treatment 64906 24 2704 6.66 p < 0.001 28725 24 1197 3.33 p < 0.001 Error 131499 324 406 116369 324 359 Total 804846 360 282475 360 Corrected total 493118 359 213516 359 Significant differences occurred between extract treatments both in coverage of uredinia (ANOVA, F 8,351 =15.06, p < 0.001) and telia (F 8,351 =5.76, p < 0.001). Coverage of uredinia was significantly higher in all the other extract treatments and methanol compared to dry control and uninoculated treatment (Tukey’s HSD, Table 3 ). Dry control did not differ significantly from uninoculated treatment, and the extract treatments and methanol control did neither differ from one another (Table 3 ). The coverage of telia was significantly higher after treatment with extracts from M. pratense , V. chamaedrys , chlorogenic acid and methanol control compared with uninoculated treatment (Table 3 ). The extract treatments including methanol and dry controls did not differ in telia coverages from one another (Table 3 ). Table 3 Percentage of uredinia and telia of Cronartium pini and C. ribicola on detached leaves of test plants, pretreated with four plant extracts, two commercial chemicals, water-methanol control, dry control, and on uninoculated leaves after 6-weeks of in vitro incubation. Shown are the mean values of 40 replicate leaves of all the test plants per treatment, standard deviation, and minimum and maximum values. Significant differences between treatments (Tukey’s HSD) are indicated with different letters at p < 0.001. Treatments Uredinia Telia x std min max x std min max Melampyrum pratense 35.41 a 38.49 0 100.0 16.55 a 22.72 0 70.5 Impatiens glandulifera 28.90 a 39.82 0 100.0 7.95 ab 19.92 0 90.0 Veronica chamaedrys 38.10 a 39.14 0 100.0 16.68 a 24.97 0 90.0 Ribes rubrum 30.85 a 38.45 0 100.0 16.08 ab 24.40 0 90.0 Chlorogenic acid 36.63 a 38.64 0 100.0 21.66 a 31.20 0 100.0 Quercitrin 32.53 a 38.82 0 90.0 12.25 ab 25.02 0 90.0 Water + methanol control 40.58 a 41.49 0 100.0 23.30 a 33.30 0 100.0 Dry control 21.85 b 24.29 0 90.0 10.10 ab 14.51 0 50.5 Control without inoculum 0 b 0 0 0 0 b 0 0 0 None of the plant extracts or commercial compounds showed significant inhibition against C. pini infection on the test leaves (Table 3 ). Among extracts, the lowest coverages of C. pini uredinia and telia occurred on the leaves treated with I. glandulifera (Table 3 ). The highest coverages of uredinia and telia occurred after methanol treatment on the plates (Table 3 ). Effect of leaf extracts on Cronartium fruiting and sporulation in the greenhouse The mean percentage of infected leaves per plant among plant species was highest on P. lactiflora in which all leaves of all plants became infected (Table 4 ). The mean percentage of infected leaves was ca. 50% on R. nigrum and ca. 18% on I. balsamina . The disease incidences differed statistically significantly between plant species (one-way ANOVA, F 2,21 =163.22, p < 0.001). All plant species differed significantly from one another according to Tukey’s test (p < 0.001, Table 4 ). The mean percentage of infected leaves per plant did not differ significantly between extract treatments (one-way ANOVA, F 7,16 =0.058, p = 1.0, Table 5 ). The highest mean disease incidence occurred after treatment with R. rubrum extract and the lowest with chlorogenic acid (Table 5 ). None of the treatments prohibited significantly rust fruiting and sporulation on leaves of test plants in the greenhouse (Table 5 ). Table 4 Mean percentage and variation of Ribes nigrum , Paeonia lactiflora and Impatiens balsamina leaves per plant bearing either uredinia or telia of Cronartium pini or C. ribicola after treatment with four plant extracts, two commercial chemicals and two controls and inoculation with either Cronartium pini or C. ribicola after 6-weeks of incubation in the greenhouse. N = Number of plants. Significant differences between plant species (Tukey’s HSD) are indicated with different letters at p < 0.001. Plant species Leaves with uredinia or telia per plant N x std min max Ribes nigrum 8 50.21 a 10.11 41.9 72.2 Paeonia lactiflora 8 100.00 b 0 100.0 100.0 Impatiens balsamina 8 18.11 c 12.17 0 70.5 Table 5 Mean percentage and variation of Ribes nigrum , Paeonia lactiflora and Impatiens balsamina leaves per plant bearing either uredinia or telia of Cronartium pini or C. ribicola after treatment with four plant extracts, two commercial chemicals and two controls and inoculation with either Cronartium pini or C. ribicola after 6-weeks of incubation in the greenhouse. N = Number of plants. Significant differences between treatments (Tukey’s HSD) are indicated with different letters at p < 0.001. Treatment with extracts Leaves with uredinia or telia per plant N x std min max Melampyrum pratense extract 3 51.07 a 46.90 6.5 100.0 Impatiens glandulifera extract 3 58.77 a 39.36 21.6 100.0 Veronica chamaedrys extract 3 55.37 a 39.74 23.8 100.0 Ribes rubrum extract 3 65.10 a 38.94 23.1 100.0 Chlorogenic acid 3 50.00 a 50.00 0 100.0 Quercitrin 3 53.77 a 41.59 19.4 100.0 Water + methanol control 3 51.97 a 45.12 11.1 100.0 Dry control 3 63.73 a 32.01 39.4 100.0 Discussion Creating eco-friendly plant-protection solutions is especially vital for commercially valuable forest species such as pines. Plants that naturally resist pathogens are a potential source of low-risk compounds that fit well into integrated pest-management programs for forest production systems (Lankinen et al., 2024). An earlier study addressed the possible role of alternate host extracts on the aeciospore germination of Cronartium rusts (Piispanen et al ., 2025). The results indicated that the effect of extracts and pure compounds on the pre-haustorial phase of rust infection was not straightforward (Piispanen et al . , 2025). Here, we tested the effect of extracts and individual pure compounds on the post-haustorial, sporulation phase of Cronartium rusts on susceptible alternate hosts. Our experiments confirmed that rust sporulation differed markedly among the test plants, i.e., rust fruiting is strongly host-dependent. Among the tested species, P. lactiflora was heavily infected by C. pini and R. nigrum by C. ribicola . On the other hand, I. balsamina was the least infected in both in vivo and in in vitro tests, in accordance with earlier studies that rated it less susceptible (Kaitera et al. 2012, 2015). In Finnish gardens, paeonies (e.g., P. lactiflora ) are appreciated ornamentals, and R. nigrum is commonly planted by households due to its berries. Given that susceptible plant species are common both in forests ( Melampyrum species) and in urban areas, Cronartium rusts will continue to be a threat to pine forestry throughout the country. Opposed to our expectation, none of the plant extracts from rust-resistant species and commercial chemicals significantly reduced fruiting and sporulation of either C. pini or C. ribicola in the in vitro tests. In contrast, all treatments, including methanol, promoted sporulation. This could indicate that the rusts were able to use the extracts or chemicals as a source of nutrients (carbon) (Blumenstein et al . , 2015) or as positive signaling molecules (Mandal et al., 2010). In addition, while most extracts and pure chemicals tended to result in lower mean sporulation on intact ( in vivo ) plants, none of the treatments showed a clear and strong inhibitory effect. These inconsistent trends across the in vitro and in vivo tests further suggest that the tested plant extracts and chemicals, administered as spray treatment, are not promising protectants against Cronartium rusts. However, we cannot exclude that different concentration of extracts or pure compounds might have influenced rust fruiting differently. In our recent study, plant extracts with 50 and 100 ppm had stimulative effect on germination of C. pini and C. ribicola aeciospores on agar, while 500 ppm inhibited strongly spore germination (Piispanen et al., 2025). Thus, testing of plant extracts should be continued with higher concentrations and different solvents. Declarations Ethics declarations The authors bear all the ethical responsibilities of this manuscript. They declare that the research was conducted in the absence of any commercial or financial relationship that could be construed as a potential conflict of interest and that it does not include any animal and/or human trials. Funding Open access funding provided by Natural Resources Institute Finland (LUKE). Data availability The data that support the findings of this study are available from the corresponding author upon reasonable request. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ Acknowledgements We thank Timo Mikkonen and Annika Uimonen for helping in the laboratory and greenhouse work. The study was financed by the Finnish Academy of Science (grant no. 332811). References Blumenstein, K., Albrectsen, B. R., Martín, J. A., Hultberg, M. Sieber, T. Helander, M., & Witzell. J. (2015) . Nutritional niche overlap potentiates the use of endophytes in biocontrol of a tree disease. BioControl 60 , 655–667. Boyer, M. G. (1964). Studies on white pine phenols in relation to blister rust. Canadian Journal of Botany, 42 , 979-987. Bullington, L.S., Lekberg, Y., Sniezko, R., & Larkin, B. (2018). The influence of genetics, defensive chemistry and the fungal microbiome on disease outcome in whitebark pine trees. Molecular Plant Pathology, 19, 1847–58. CABI. (2020). Cronartium flaccidum (Scots pine blister rust) in: Invasive Species Compendium. Wallingford, UK: CAB International. 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Naumov, P., Kuzmanovski, I., & Stefova, M. (1998). Flavonoids of Verbascum scardicolum and Melampyrum scardicum . Bulletin of the Chemists and Technologists of Macedonia, 17(1) , 41-44. Piispanen, J., Bergmann, U., Karhu, J., Kauppila, T., & Kaitera, J. (2023). Variation of compounds in leaves of susceptible and resistant alternate hosts of Cronartium pini and C. ribicola . European Journal of Plant Pathology, 165(4) , 677-692. Piispanen, J., Bergmann, U., Karhu, J., Kauppila, T., Witzell, J. & Kaitera, J. (2025). Effect of leaf chemicals from susceptible and resistant alternate hosts of Cronartium on in vitro germination of aeciospores of Cronartium pini and C. ribicola . Baltic Forestry , 31(1) , 12-17. Sniezko, R. A., Smith, J., Liu, J.-J., & Hamelin, R. C. (2014). Genetic resistance to fusiform rust in southern pines and white pine blister rust in white pines – a contrasting tale of two rust pathosystems - current status and future prospects. Forests, 5(9) , 2050-2083. Wulff, S., Lindelöw, Å., Lundin, L., Hansson, P., Axelsson, A.-L., Barklund, P., Wijk, S., & Ståhl, G. (2012). Adapting forest health assessments to changing perspectives on threats – a case example from Sweden. Environmental Monitoring Assessments, 184 , 2453-2464. Zambino, P. J. (2010). Biology and pathology of Ribes and their implications for management of white pine blister rust. Forest Pathology, 40 , 264–291. Cite Share Download PDF Status: Posted Version 1 posted 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-8191801","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":555114852,"identity":"1104abdd-0286-4250-9856-2573aa9d5731","order_by":0,"name":"Juha Piispanen","email":"","orcid":"","institution":"Natural Resources Institute Finland: Luonnonvarakeskus","correspondingAuthor":false,"prefix":"","firstName":"Juha","middleName":"","lastName":"Piispanen","suffix":""},{"id":555114853,"identity":"779691af-5a37-4e5c-a34f-daf27c73a1b7","order_by":1,"name":"Ulrich Bergmann","email":"","orcid":"","institution":"University of Oulu Biocenter: Oulu yliopisto Biocenter","correspondingAuthor":false,"prefix":"","firstName":"Ulrich","middleName":"","lastName":"Bergmann","suffix":""},{"id":555114854,"identity":"3fdcccb8-dd80-4cba-ac96-3b940b846e47","order_by":2,"name":"Jouni Karhu","email":"","orcid":"","institution":"Natural Resources Institute Finland: Luonnonvarakeskus","correspondingAuthor":false,"prefix":"","firstName":"Jouni","middleName":"","lastName":"Karhu","suffix":""},{"id":555114855,"identity":"3e1e66ec-948e-4a7d-8c37-3ab7ba00f2cd","order_by":3,"name":"Tuomas Kauppila","email":"","orcid":"","institution":"University of Oulu: Oulun Yliopisto","correspondingAuthor":false,"prefix":"","firstName":"Tuomas","middleName":"","lastName":"Kauppila","suffix":""},{"id":555114856,"identity":"916d765c-4752-4249-bc67-e253892b3e0f","order_by":4,"name":"Johanna Witzell","email":"","orcid":"","institution":"Linnaeus University: Linneuniversitetet","correspondingAuthor":false,"prefix":"","firstName":"Johanna","middleName":"","lastName":"Witzell","suffix":""},{"id":555114857,"identity":"8b16bb3c-9d20-44ea-9627-d8a79f4a22e8","order_by":5,"name":"Juha Kaitera","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA60lEQVRIie2OsWoCQRCG/2PgbAZsTwz4CiMLh6LkXkUQTHMJloEUOUhxjWJ7j7NyoM09wJVJY2WxkEZIkz1jk2Y3ZYr9ihlmdj/mBwKBf0hUsK0afJ3MGmJ37/pPSteiSjqFxKkAP8q1Ed8Up0DV496gub/LetuPz7nUqg+K3MGqp2WCdsnMRzXMpU4HBcGj5JLAEHOyQqfMRfe1T1EXmFfm0Ym+JlbJtP9KaoPV9kocD2GDCXzK5pxOFs2RuVnF0408qKT2KOMyV605vGS98kDt5Xk23pVvZJxKYcvi14pc/y0jz3sgEAgEgG/ZdUMH3xLeAwAAAABJRU5ErkJggg==","orcid":"","institution":"Natural Resources Institute Finland: Luonnonvarakeskus","correspondingAuthor":true,"prefix":"","firstName":"Juha","middleName":"","lastName":"Kaitera","suffix":""}],"badges":[],"createdAt":"2025-11-24 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J\u0026oslash;rst. is a pathogen that kills pine (\u003cem\u003ePinus\u003c/em\u003e spp.) trees in Europe and Asia (G\u0026auml;umann, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1959\u003c/span\u003e; CABI, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The rust is also a quarantine species in North America (Kim et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In the 2000s, \u003cem\u003eC. pini\u003c/em\u003e caused severe losses on young \u003cem\u003ePinus sylvestris\u003c/em\u003e L. plantations in northern Europe, especially in nutrient-rich soils (Kaitera, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Wulff et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), although the rust was previously known especially as a disease of mature pines on poor sites (Kaitera et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). Another \u003cem\u003eCronartium, C. ribicola\u003c/em\u003e Fisch., is a serious pathogen of five-needle pines especially in North America (Zambino, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cem\u003eCronartium pini\u003c/em\u003e spreads via alternate hosts of over 50 susceptible species in 14 plant families (Kaitera et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Kim et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The most important alternate host species belong to hemiparasites in Orobanchaceae (Kaitera, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Kaitera et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1999\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2012\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2015\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kaitera \u0026amp; Nuorteva, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2003a\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003eb\u003c/span\u003e). In genus \u003cem\u003eMelampyrum\u003c/em\u003e, \u003cem\u003eM. sylvaticum\u003c/em\u003e L., \u003cem\u003eM. nemorosum\u003c/em\u003e L., \u003cem\u003eM. arvense\u003c/em\u003e L. and \u003cem\u003eM. cristatum\u003c/em\u003e L. are highly susceptible, while \u003cem\u003eM. pratense\u003c/em\u003e shows resistance against \u003cem\u003eC. pini\u003c/em\u003e (Kaitera, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Kaitera et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). \u003cem\u003eCronartium ribicola\u003c/em\u003e spreads via plants in genus \u003cem\u003eRibes\u003c/em\u003e (Grossulariaceae). In Finland, most \u003cem\u003eR. nigrum\u003c/em\u003e cultivars are susceptible, while \u003cem\u003eR. rubrum\u003c/em\u003e cultivars show resistance against \u003cem\u003eC. ribicola\u003c/em\u003e (Kaitera \u0026amp; Nuorteva, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2006\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eRecent studies have shown that chemical composition of \u003cem\u003eP. sylvestris\u003c/em\u003e wood changes after \u003cem\u003eC. pini\u003c/em\u003e infection (Kaitera et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), suggesting that terpenes and resin acids are produced by the host as defensive chemicals against \u003cem\u003eCronartium\u003c/em\u003e. Terpenes have been linked to \u003cem\u003eC. ribicola\u003c/em\u003e resistance in \u003cem\u003ePinus\u003c/em\u003e also earlier (Michelozzi et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Bullington et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) and also phenolic compounds have been assigned defensive roles in pine resistance against \u003cem\u003eCronartium\u003c/em\u003e rusts (Boyer, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1964\u003c/span\u003e; Hanover \u0026amp; Hoff, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1966\u003c/span\u003e; Hudgins et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Sniezko et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). The possible role of phenolics in alternate host resistance against \u003cem\u003eCronartium\u003c/em\u003e has also been studied, in both the susceptible and resistant species (e.g., Piispanen et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). It has been suggested that variation in rust resistance between the closely related species such as \u003cem\u003eM. sylvaticum\u003c/em\u003e and \u003cem\u003eM. pratense\u003c/em\u003e may be due to variation in leaf phenolic chemistry (Kaitera \u0026amp; Witzell, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Polyphenolics, such as luteolin and apigenin flavonoids with documented antimicrobial impact on bacterial, viral and fungal pathogens (Cushnie \u0026amp; Lamb, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) occur at high concentrations in some \u003cem\u003eMelampyrum\u003c/em\u003e species (Naumov et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). Recently, chlorogenic acid (Kaitera \u0026amp; Witzell, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Piispanen et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) and quercitrin (Piispanen et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) were found to be enriched in \u003cem\u003eC. pini\u003c/em\u003e-resistant \u003cem\u003eM. pratense\u003c/em\u003e.\u003c/p\u003e\u003cp\u003eWith tightening regulations on environmentally harmful synthetic fungicides, there is an urgent demand for bio-based, sustainable methods to manage tree diseases both in nurseries and in the field. The aim of this study was to explore whether extracts from alternate hosts could be useful as bio-based suppressants against \u003cem\u003eCronartium\u003c/em\u003e. Therefore, we conducted \u003cem\u003ein vivo\u003c/em\u003e and \u003cem\u003ein vitro\u003c/em\u003e studies to investigate the effect of leaf extracts from selected resistant alternate hosts of \u003cem\u003eC. pini\u003c/em\u003e and \u003cem\u003eC. ribicola\u003c/em\u003e on the fruiting and sporulation of \u003cem\u003eCronartium\u003c/em\u003e species. We hypothesized that the externally added extracts from resistant alternative host species could suppress the fruiting and sporulation of \u003cem\u003eCronartium\u003c/em\u003e rusts on the susceptible hosts.\u003c/p\u003e"},{"header":"Material and methods","content":"\u003cp\u003ePlant material for extracts\u003c/p\u003e\u003cp\u003ePlant species resistant to \u003cem\u003eC. pini\u003c/em\u003e, i.e., \u003cem\u003eM. pratense\u003c/em\u003e (65\u0026deg;2,69N, 25\u0026deg;28,04E), \u003cem\u003eImpatiens glandulifera\u003c/em\u003e Royle (65\u0026deg;3,86N, 25\u0026deg;27,79E) and \u003cem\u003eVeronica chamaedrys\u003c/em\u003e L. (65\u0026deg;1,30N, 25\u0026deg;25,96E), were from natural habitats in the city area of Oulu in northern Finland, while species resistant to \u003cem\u003eC. ribicola\u003c/em\u003e were commercial seedlings of \u003cem\u003eRibes rubrum\u003c/em\u003e L. from a commercial nursery (S\u0026auml;rk\u0026auml;n taimitarha). Plants were collected and transported to the laboratory, where their healthy leaves were detached, air-dried and used for preparation of leaf extracts.\u003c/p\u003e\u003cp\u003ePlant material for inoculations\u003c/p\u003e\u003cp\u003eFor the laboratory experiment, healthy leaves of susceptible \u003cem\u003eM. sylvaticum\u003c/em\u003e were collected from the city area of Oulu in early July 2021. In addition, leaves of commercial plants of susceptible \u003cem\u003eR. nigrum\u003c/em\u003e and \u003cem\u003ePaeonia lactiflora\u003c/em\u003e Pall from the nursery (S\u0026auml;rk\u0026auml;n taimitarha), and \u003cem\u003eImpatiens balsamina\u003c/em\u003e L. grown from seeds in the Botanical Gardens of Oulu University in May 2021, were used in the laboratory experiments. Whole plants of the above mentioned \u003cem\u003eR. nigrum\u003c/em\u003e, \u003cem\u003eP. lactiflora\u003c/em\u003e and \u003cem\u003eI. balsamina\u003c/em\u003e were also used in the greenhouse experiment.\u003c/p\u003e\u003cp\u003ePreparation of plant extracts\u003c/p\u003e\u003cp\u003eIn the laboratory, healthy green leaves of the rust-resistant plants were separated from the rest of the plant material aseptically with sterile tweezers. The leaves were air-dried for about a week in the laminar cabin in open paper bags and stored at -20\u0026deg;C prior to extraction. The leaf samples were crushed manually inside a paper bag until a powdery consistency was achieved. Of each sample,1 g was extracted in 40 mL methanol (HPLC grade, Merck, 1.06007.2500)(for the extraction, see Piispanen et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The extracts were kept at +\u0026thinsp;4 \u0026ordm;C for 24 hours and diluted to 100 mL by sterile water. In addition, solutions of commercial compounds, potentially linked to resistance of \u003cem\u003eCronartium\u003c/em\u003e rusts based on the results of earlier studies (Kaitera \u0026amp; Witzell, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Piispanen et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), were also tested: chlorogenic acid (Acros Organics, 109.240.010) and quercitrin (Cayman Chemical Company, CAYM19866), 5 g each, were dissolved to 100 ml of sterile water: methanol (40:60 v/v). The further diluted solutions for the experiments were made daily from these base solutions (100 ppm for plant extracts and 0,5 ppm for chlorogenic acid and quercitrin). The methanol-water control solutions contained same amount of methanol than the plant extracts used in the experiments.\u003c/p\u003e\u003cp\u003eInoculum and inoculation treatments\u003c/p\u003e\u003cp\u003eAeciospores of \u003cem\u003eC. pini\u003c/em\u003e were collected from Kolari (67\u0026ordm;9,64N, 23\u0026ordm;40,06E), northern Finland, in mid-June (June 13) 2021. The collection site was a \u003cem\u003eP. sylvestris\u003c/em\u003e stand where the presence and pathogenicity of the rust had been confirmed (Kaitera et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Five branches bearing \u003cem\u003eC. pini\u003c/em\u003e lesions were cut and transported to the Lynet laboratory of the Natural Resources Institute Finland in Oulu. Aeciospores were released into sterile Petri dishes by cutting the surface of aecia aseptically in a laminar cabin using a scalpel. Aeciospores of \u003cem\u003eC. ribicola\u003c/em\u003e were then dusted from \u003cem\u003ePinus cembra\u003c/em\u003e L. directly to Petri dishes in the field by cutting the surface of aecia from four lesions in Oulunsalo (64\u0026ordm;56,50N, 25\u0026ordm;22,60E) in late May (May 28) 2021. The aeciospores of both species were stored at 5\u0026deg;C before usage. Germination of the spores was measured by dusting spores on 1.5% water agar, incubating the plates at 21.5\u0026deg;C in the daylight for 24 h, and counting germination from 10 microscopic areas on agar using a light microscope (Mx4300H, Meiji Techno Co., LTD). Mean germination of \u003cem\u003eC. pini\u003c/em\u003e was 94% (87\u0026ndash;98%) and of \u003cem\u003eC. ribicola\u003c/em\u003e 85% (81\u0026ndash;91%).\u003c/p\u003e\u003cp\u003eLaboratory (\u003cem\u003ein vitro\u003c/em\u003e) experiment\u003c/p\u003e\u003cp\u003eFive Petri dishes were prepared with two leaves of each susceptible alternate host (\u003cem\u003eR. nigrum, M. sylvaticum\u003c/em\u003e, \u003cem\u003eP. lactiflora\u003c/em\u003e, and \u003cem\u003eI. balsamina\u003c/em\u003e and) per plate floating on sterilized water in the laboratory experiment. Prior to inoculation, leaves were treated with extracts (one extract per plate). Four extracts were from \u003cem\u003eM. pratense\u003c/em\u003e, \u003cem\u003eI. glandulifera\u003c/em\u003e, \u003cem\u003eV. chamaedrys\u003c/em\u003e and \u003cem\u003eR. rubrum\u003c/em\u003e, and chlorogenic acid and quercitrin were used as additional commercial compounds. Two controls were included: methanol-water (40:60, v/v) and dry leaves without methanol or water. The plant extracts were used at 100 ppm and commercial compounds at concentration of 0.5 ppm. The leaves were soaked in extracts, solutions or pure water:methanol for 5 sec, except for the dry control. After treatments, aeciospores of \u003cem\u003eC. pini\u003c/em\u003e were dusted using an artist\u0026rsquo;s pencil on leaves of \u003cem\u003eM. sylvaticum\u003c/em\u003e, \u003cem\u003eP. lactiflora\u003c/em\u003e and \u003cem\u003eI. balsamina\u003c/em\u003e, while \u003cem\u003eC. ribicola\u003c/em\u003e was dusted on \u003cem\u003eR. nigrum\u003c/em\u003e. Plates without inoculation were included to control for natural infections on the leaves. The plates were incubated for 6 weeks at 18\u0026deg;C in the dark in a growth chamber (KB240, Binder GmbH, Tuttlingen, Germany). After the incubations, the leaves were checked using a stereomicroscope (M5A, Wild Heerbrugg, Switzerland) to determine the coverage of uredinia and telia per leaf using classes \u0026lsquo;0%\u0026rsquo;, \u0026lsquo;1\u0026ndash;20%\u0026rsquo;, \u0026rsquo;21\u0026ndash;40%\u0026rsquo;, \u0026rsquo;41\u0026ndash;60%\u0026rsquo;, \u0026rsquo;61\u0026ndash;80%\u0026rsquo;, \u0026rsquo;81\u0026ndash;99%\u0026rsquo; and \u0026lsquo;100%\u0026rsquo;. Later, the mean percentages of these classes were used in the calculations.\u003c/p\u003e\u003cp\u003eGreenhouse (\u003cem\u003ein vivo\u003c/em\u003e) experiment\u003c/p\u003e\u003cp\u003eIn the greenhouse, eight plants per species were prepared for the experiment. All leaves of \u003cem\u003eP. lactiflora\u003c/em\u003e and \u003cem\u003eI. balsamina\u003c/em\u003e, and leaves from one branch of \u003cem\u003eR. nigrum\u003c/em\u003e per plant, were sprayed with six extracts and two controls. One extract or control was sprayed per plant. The extracts were the same as in the laboratory experiment. As controls, a methanol:water (40:60, v/v) treatment and a water treatment were used. The sprayed leaves of \u003cem\u003eP. lactiflora\u003c/em\u003e and \u003cem\u003eI. balsamina\u003c/em\u003e plants were thereafter dusted with \u003cem\u003eC. pini\u003c/em\u003e and those of \u003cem\u003eR. nigrum\u003c/em\u003e with \u003cem\u003eC. ribicola\u003c/em\u003e aeciospores with an artist\u0026rsquo;s pencil. After inoculation, the plants were covered with a plastic bag for 48 h to promote spore germination. After 6 weeks of incubation, the leaves were collected and the numbers of leaves carrying uredinia or telia were counted using a stereomicroscope in the laboratory (see above). The infection percentage was used to indicate the success of infection.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eThe effect of extract treatment, plant species and their interaction on coverage of uredinia and telia was modelled using ANOVA of SAS (SAS Institute Inc., version 9.4). The data from the laboratory experiment (6 week\u0026rsquo;s inoculation) was subjected to one-way analysis of variance with the GLM procedure and the Tukey\u0026rsquo;s Studentized Range (HSD) post hoc test to test. For the data from the greenhouse experiment, infection percentage of leaves (%) was compared separately between plant species and treatments using also one-way analysis of variance and Tukey\u0026rsquo;s (HSD) test.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cem\u003eCronartium\u003c/em\u003e fruiting and sporulation \u003cem\u003ein vitro\u003c/em\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003eIn vitro\u003c/em\u003e inoculations were successful, resulting in mean uredinia coverage values ranging from 5% (\u003cem\u003eC. pini\u003c/em\u003e on \u003cem\u003eM. sylvaticum\u003c/em\u003e) to ca. 70% (\u003cem\u003eC. ribicola\u003c/em\u003e on \u003cem\u003eR. nigrum\u003c/em\u003e), and mean telia coverage values ranging from ca. 6% (\u003cem\u003eC. pini\u003c/em\u003e on \u003cem\u003eM. sylvaticum\u003c/em\u003e) to 35% (\u003cem\u003eC. pini\u003c/em\u003e on \u003cem\u003eP. lactiflora\u003c/em\u003e) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Natural infections were not found on the uninoculated leaves.\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\u003eMean coverage (x) and standard deviation (std) of uredinia and telia on detached leaf after inoculation with \u003cem\u003eCronartium pini\u003c/em\u003e on \u003cem\u003eMelampyrum sylvaticum\u003c/em\u003e, \u003cem\u003ePaeonia lactiflora\u003c/em\u003e and \u003cem\u003eImpatiens balsamina\u003c/em\u003e, and \u003cem\u003eC. ribicola\u003c/em\u003e on \u003cem\u003eRibes nigrum\u003c/em\u003e in the laboratory after 6-weeks of incubation (n\u0026thinsp;=\u0026thinsp;90 per plant species). Different letters after mean values indicate significant difference (Tukey\u0026rsquo;s HSD) at p\u0026thinsp;\u0026lt;\u0026thinsp;0.001.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePlant species\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e\u003cp\u003eFruiting stages\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e\u003cp\u003eUredinia\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c9\" namest=\"c6\"\u003e\u003cp\u003eTelia\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003estd\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003emin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003emax\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003estd\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003emin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003emax\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eRibes nigrum\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e69.60\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e33.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e9.08\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e11.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e70.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eMelampyrum sylvaticum\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.42\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e50.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e5.65\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e13.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e50.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003ePaeonia lactiflora\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e36.05\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35.96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e34.51\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e36.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eImpatiens balsamina\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6.63\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e13.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e70.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e6.12\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e13.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e70.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eSignificant differences occurred between plant species in the mean coverage of uredinia (ANOVA, F\u003csub\u003e3,356\u003c/sub\u003e=205.53, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and telia (F\u003csub\u003e3,356\u003c/sub\u003e=48.14, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) after six weeks of incubation time (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). In pairwise comparisons, significant differences in coverage of uredinia were found between all species except between \u003cem\u003eM. sylvaticum\u003c/em\u003e and \u003cem\u003eI. balsamina\u003c/em\u003e (Tukey\u0026rsquo;s HSD, Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The coverage of telia differed significantly only between \u003cem\u003eP. lactiflora\u003c/em\u003e and the other three species (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\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\u003eANOVA table on the effect of plant extract treatments on uredinia and telia formation after inoculation of leaves of four test plants (\u003cem\u003eR. nigrum\u003c/em\u003e, \u003cem\u003eM. sylvaticum\u003c/em\u003e, \u003cem\u003eP. laciflora\u003c/em\u003e and \u003cem\u003eI. balsamina\u003c/em\u003e) with \u003cem\u003eCronartium pini\u003c/em\u003e or \u003cem\u003eC. ribicola\u003c/em\u003e after incubation of six weeks in the laboratory.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"11\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" 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=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c6\" namest=\"c3\"\u003e\u003cp\u003eUredinia\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"5\" nameend=\"c11\" namest=\"c7\"\u003e\u003cp\u003eTelia\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSource\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eType III SS\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDF\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMS\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eF\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eP\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eType III SS\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eDF\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eMS\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eF\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u003cp\u003eP\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCorrected\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e361619\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e10332\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e25.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e97147\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e2776\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e7.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntercept\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e311729\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e311729\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e768.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e68959\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e68959\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e192.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpecies\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e247816\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e82605\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e203.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e51869\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e17290\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e48.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTreatment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e48896\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6112\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e15.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e16553\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e2069\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e5.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpecies x Treatment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e64906\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2704\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e6.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e28725\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e1197\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e3.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eError\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e131499\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e324\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e406\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e116369\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e324\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e359\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e804846\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e360\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e282475\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e360\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCorrected total\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e493118\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e359\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e213516\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e359\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eSignificant differences occurred between extract treatments both in coverage of uredinia (ANOVA, F\u003csub\u003e8,351\u003c/sub\u003e=15.06, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and telia (F\u003csub\u003e8,351\u003c/sub\u003e=5.76, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Coverage of uredinia was significantly higher in all the other extract treatments and methanol compared to dry control and uninoculated treatment (Tukey\u0026rsquo;s HSD, Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Dry control did not differ significantly from uninoculated treatment, and the extract treatments and methanol control did neither differ from one another (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The coverage of telia was significantly higher after treatment with extracts from \u003cem\u003eM. pratense\u003c/em\u003e, \u003cem\u003eV. chamaedrys\u003c/em\u003e, chlorogenic acid and methanol control compared with uninoculated treatment (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The extract treatments including methanol and dry controls did not differ in telia coverages from one another (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\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\u003ePercentage of uredinia and telia of \u003cem\u003eCronartium pini\u003c/em\u003e and \u003cem\u003eC. ribicola\u003c/em\u003e on detached leaves of test plants, pretreated with four plant extracts, two commercial chemicals, water-methanol control, dry control, and on uninoculated leaves after 6-weeks of \u003cem\u003ein vitro\u003c/em\u003e incubation. Shown are the mean values of 40 replicate leaves of all the test plants per treatment, standard deviation, and minimum and maximum values. Significant differences between treatments (Tukey\u0026rsquo;s HSD) are indicated with different letters at p\u0026thinsp;\u0026lt;\u0026thinsp;0.001.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTreatments\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e\u003cp\u003eUredinia\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c9\" namest=\"c6\"\u003e\u003cp\u003eTelia\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003estd\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003emin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003emax\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003estd\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003emin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003emax\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eMelampyrum pratense\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35.41\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e38.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e16.55\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e22.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e70.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eImpatiens glandulifera\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e28.90\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e39.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e7.95\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e19.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e90.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eVeronica chamaedrys\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e38.10\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e39.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e16.68\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e24.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e90.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eRibes rubrum\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30.85\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e38.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e16.08\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e24.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e90.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChlorogenic acid\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e36.63\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e38.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e21.66\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e31.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eQuercitrin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e32.53\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e38.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e90.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e12.25\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e25.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e90.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWater\u0026thinsp;+\u0026thinsp;methanol control\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e40.58\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e41.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e23.30\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e33.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDry control\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e21.85\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e90.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e10.10\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e14.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e50.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eControl without inoculum\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eNone of the plant extracts or commercial compounds showed significant inhibition against \u003cem\u003eC. pini\u003c/em\u003e infection on the test leaves (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Among extracts, the lowest coverages of \u003cem\u003eC. pini\u003c/em\u003e uredinia and telia occurred on the leaves treated with \u003cem\u003eI. glandulifera\u003c/em\u003e (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The highest coverages of uredinia and telia occurred after methanol treatment on the plates (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cb\u003eEffect of leaf extracts on\u003c/b\u003e \u003cb\u003eCronartium\u003c/b\u003e \u003cb\u003efruiting and sporulation in the greenhouse\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe mean percentage of infected leaves per plant among plant species was highest on \u003cem\u003eP. lactiflora\u003c/em\u003e in which all leaves of all plants became infected (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The mean percentage of infected leaves was ca. 50% on \u003cem\u003eR. nigrum\u003c/em\u003e and ca. 18% on \u003cem\u003eI. balsamina\u003c/em\u003e. The disease incidences differed statistically significantly between plant species (one-way ANOVA, F\u003csub\u003e2,21\u003c/sub\u003e=163.22, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). All plant species differed significantly from one another according to Tukey\u0026rsquo;s test (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The mean percentage of infected leaves per plant did not differ significantly between extract treatments (one-way ANOVA, F\u003csub\u003e7,16\u003c/sub\u003e=0.058, p\u0026thinsp;=\u0026thinsp;1.0, Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The highest mean disease incidence occurred after treatment with \u003cem\u003eR. rubrum\u003c/em\u003e extract and the lowest with chlorogenic acid (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). None of the treatments prohibited significantly rust fruiting and sporulation on leaves of test plants in the greenhouse (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cb\u003eMean percentage and variation of\u003c/b\u003e \u003cem\u003eRibes nigrum\u003c/em\u003e, \u003cb\u003ePaeonia lactiflora\u003c/b\u003e \u003cb\u003eand\u003c/b\u003e \u003cb\u003eImpatiens balsamina\u003c/b\u003e \u003cb\u003eleaves per plant bearing either uredinia or telia of\u003c/b\u003e \u003cb\u003eCronartium pini\u003c/b\u003e \u003cb\u003eor\u003c/b\u003e \u003cb\u003eC. ribicola\u003c/b\u003e \u003cb\u003eafter treatment with four plant extracts, two commercial chemicals and two controls and inoculation with either\u003c/b\u003e \u003cb\u003eCronartium pini\u003c/b\u003e \u003cb\u003eor\u003c/b\u003e \u003cb\u003eC. ribicola\u003c/b\u003e \u003cb\u003eafter 6-weeks of incubation in the greenhouse. N\u0026thinsp;=\u0026thinsp;Number of plants. Significant differences between plant species (Tukey\u0026rsquo;s HSD) are indicated with different letters at p\u0026thinsp;\u0026lt;\u0026thinsp;0.001.\u003c/b\u003e\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\u003ePlant species\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"5\" nameend=\"c6\" namest=\"c2\"\u003e\u003cp\u003eLeaves with uredinia or telia per plant\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eN\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003estd\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003emin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003emax\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eRibes nigrum\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50.21\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e41.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e72.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003ePaeonia lactiflora\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e100.00\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eImpatiens balsamina\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18.11\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e12.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e70.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cb\u003eMean percentage and variation of\u003c/b\u003e \u003cem\u003eRibes nigrum\u003c/em\u003e, \u003cb\u003ePaeonia lactiflora\u003c/b\u003e \u003cb\u003eand\u003c/b\u003e \u003cb\u003eImpatiens balsamina\u003c/b\u003e \u003cb\u003eleaves per plant bearing either uredinia or telia of\u003c/b\u003e \u003cb\u003eCronartium pini\u003c/b\u003e \u003cb\u003eor\u003c/b\u003e \u003cb\u003eC. ribicola\u003c/b\u003e \u003cb\u003eafter treatment with four plant extracts, two commercial chemicals and two controls and inoculation with either\u003c/b\u003e \u003cb\u003eCronartium pini\u003c/b\u003e \u003cb\u003eor\u003c/b\u003e \u003cb\u003eC. ribicola\u003c/b\u003e \u003cb\u003eafter 6-weeks of incubation in the greenhouse. N\u0026thinsp;=\u0026thinsp;Number of plants. Significant differences between treatments (Tukey\u0026rsquo;s HSD) are indicated with different letters at p\u0026thinsp;\u0026lt;\u0026thinsp;0.001.\u003c/b\u003e\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\u003eTreatment with extracts\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"5\" nameend=\"c6\" namest=\"c2\"\u003e\u003cp\u003eLeaves with uredinia or telia per plant\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eN\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003estd\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003emin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003emax\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eMelampyrum pratense\u003c/em\u003e extract\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e51.07\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e46.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eImpatiens glandulifera\u003c/em\u003e extract\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e58.77\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e39.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e21.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eVeronica chamaedrys\u003c/em\u003e extract\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e55.37\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e39.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e23.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cem\u003eRibes rubrum\u003c/em\u003e extract\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e65.10\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e38.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e23.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChlorogenic acid\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50.00\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e50.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eQuercitrin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e53.77\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e41.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e19.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWater\u0026thinsp;+\u0026thinsp;methanol control\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e51.97\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e45.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e11.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDry control\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e63.73\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e32.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e39.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eCreating eco-friendly plant-protection solutions is especially vital for commercially valuable forest species such as pines. Plants that naturally resist pathogens are a potential source of \u0026nbsp;low-risk compounds that fit well into integrated pest-management programs for forest production systems (Lankinen et al., 2024). An earlier study addressed the possible role of alternate host extracts on the aeciospore germination of \u003cem\u003eCronartium\u0026nbsp;\u003c/em\u003erusts (Piispanen et al\u003cem\u003e.,\u003c/em\u003e 2025). The results indicated that the effect of extracts and pure compounds on the pre-haustorial phase of rust infection was not straightforward (Piispanen et al\u003cem\u003e.\u003c/em\u003e, 2025). Here, we tested the effect of extracts and individual pure compounds on the post-haustorial, sporulation phase of \u003cem\u003eCronartium\u003c/em\u003e rusts on susceptible alternate hosts.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; \u0026nbsp;Our experiments confirmed that rust sporulation differed markedly among the test plants, i.e., \u0026nbsp;rust fruiting is strongly host-dependent. Among the tested species, \u003cem\u003eP. lactiflora\u003c/em\u003e was heavily infected by \u003cem\u003eC. pini\u003c/em\u003e and \u003cem\u003eR. nigrum\u003c/em\u003e by \u003cem\u003eC. ribicola\u003c/em\u003e. On the other hand, \u003cem\u003eI. balsamina\u003c/em\u003e was the least infected in both \u003cem\u003ein vivo\u003c/em\u003e and in \u003cem\u003ein vitro\u003c/em\u003e tests, in accordance with earlier studies that rated it less susceptible (Kaitera et al. 2012, 2015). In Finnish gardens, paeonies (e.g., \u003cem\u003eP. lactiflora\u003c/em\u003e) are appreciated ornamentals, and \u003cem\u003eR. nigrum\u003c/em\u003e is commonly planted by households due to its berries. Given that susceptible plant species are common both in forests (\u003cem\u003eMelampyrum\u003c/em\u003e species) and in urban areas, \u003cem\u003eCronartium\u003c/em\u003e rusts will continue to be a threat to pine forestry throughout the country. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; \u0026nbsp;Opposed to our expectation, none of the plant extracts from rust-resistant species and commercial chemicals significantly reduced fruiting and sporulation of either \u003cem\u003eC. pini\u003c/em\u003e or \u003cem\u003eC. ribicola\u0026nbsp;\u003c/em\u003ein the \u003cem\u003ein vitro\u003c/em\u003e tests. In contrast, all treatments, including methanol, promoted sporulation. This could indicate that the rusts were able to use the extracts or chemicals as a source of nutrients (carbon) (Blumenstein et al\u003cem\u003e.\u003c/em\u003e, 2015) or as positive signaling molecules (Mandal et al., 2010). In addition, while most extracts and pure chemicals tended to result in lower mean sporulation on intact (\u003cem\u003ein vivo\u003c/em\u003e) plants, none of the treatments showed a clear and strong inhibitory effect. These inconsistent trends across the \u003cem\u003ein vitro\u003c/em\u003e and \u003cem\u003ein vivo\u0026nbsp;\u003c/em\u003etests further suggest that the tested plant extracts and chemicals, administered as spray treatment, are not promising protectants against \u003cem\u003eCronartium\u003c/em\u003e rusts. However, we cannot exclude that different concentration of extracts or pure compounds might have influenced rust fruiting differently. In our recent study, plant extracts with 50 and 100 ppm had stimulative effect on germination of \u003cem\u003eC. pini\u003c/em\u003e and \u003cem\u003eC. ribicola\u003c/em\u003e aeciospores on agar, while 500 ppm inhibited strongly spore germination (Piispanen et al., 2025). Thus, testing of plant extracts should be continued with higher concentrations and different solvents.\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors bear all the ethical responsibilities of this manuscript. They declare that the research was conducted in the absence of any commercial or financial relationship that could be construed as a potential conflict of interest and that it does not include any animal and/or human trials.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e Open access funding provided by Natural Resources Institute Finland (LUKE).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003eThe data that support the findings of this study are available from the corresponding author upon reasonable request.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOpen Access\u003c/strong\u003e This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank Timo Mikkonen and Annika Uimonen for helping in the laboratory and greenhouse work. The study was financed by the Finnish Academy of Science (grant no. 332811).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eBlumenstein, K., Albrectsen, B. R., Mart\u0026iacute;n, J. A., Hultberg, M. Sieber, T. Helander, M., \u0026amp; Witzell. J. 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Flavonoids of \u003cem\u003eVerbascum scardicolum\u003c/em\u003e and \u003cem\u003eMelampyrum scardicum\u003c/em\u003e. \u003cem\u003eBulletin of the Chemists and\u003c/em\u003e \u003cem\u003eTechnologists of Macedonia, 17(1)\u003c/em\u003e, 41-44.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003ePiispanen, J., Bergmann, U., Karhu, J., Kauppila, T., \u0026amp; Kaitera, J. (2023).\u0026nbsp;\u0026nbsp;Variation of compounds in leaves of susceptible and resistant alternate hosts of \u003cem\u003eCronartium pini\u003c/em\u003e and \u003cem\u003eC. ribicola\u003c/em\u003e. \u003cem\u003eEuropean Journal of Plant Pathology, 165(4)\u003c/em\u003e, 677-692.\u003c/li\u003e\n \u003cli\u003ePiispanen, J., Bergmann, U., Karhu, J., Kauppila, T., Witzell, J. \u0026amp; Kaitera, J. (2025). Effect of leaf chemicals from susceptible and resistant alternate hosts of \u003cem\u003eCronartium\u003c/em\u003e on \u003cem\u003ein vitro\u003c/em\u003e germination of aeciospores of \u003cem\u003eCronartium pini\u003c/em\u003e and \u003cem\u003eC. ribicola\u003c/em\u003e.\u0026nbsp;\u003cem\u003eBaltic Forestry\u003c/em\u003e, \u003cem\u003e31(1)\u003c/em\u003e, 12-17.\u003c/li\u003e\n \u003cli\u003eSniezko, R. A., Smith, J., Liu, J.-J., \u0026amp; Hamelin, R. C. (2014). Genetic resistance to fusiform rust in southern pines and white pine blister rust in white pines \u0026ndash; a contrasting tale of two rust pathosystems - current status and future prospects. \u003cem\u003eForests, 5(9)\u003c/em\u003e, 2050-2083.\u003c/li\u003e\n \u003cli\u003eWulff, S., Lindel\u0026ouml;w, \u0026Aring;., Lundin, L., Hansson, P., Axelsson, A.-L., Barklund, P., Wijk, S., \u0026amp; St\u0026aring;hl, G. (2012). Adapting forest health assessments to changing perspectives on threats \u0026ndash; a case example from Sweden. \u003cem\u003eEnvironmental Monitoring Assessments, 184\u003c/em\u003e, 2453-2464.\u003c/li\u003e\n \u003cli\u003eZambino, P. J. (2010). Biology and pathology of \u003cem\u003eRibes\u003c/em\u003e and their implications for management of white pine blister rust. \u003cem\u003eForest Pathology,\u003c/em\u003e \u003cem\u003e40\u003c/em\u003e, 264\u0026ndash;291.\u003cstrong\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Alternate hosts, Leaf extracts, Rust resistance, Scots pine blister rust, White-pine blister rust","lastPublishedDoi":"10.21203/rs.3.rs-8191801/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8191801/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eResistance of plants to rust fungi may depend on the chemical quality of plants, suggesting that leaf extracts from resistant plant species could be useful in development of bio-based solutions against rust diseases. Pine trees (\u003cem\u003ePinus\u003c/em\u003e spp.) are affected by \u003cem\u003eCronartium\u003c/em\u003erusts (\u003cem\u003eC. pini\u003c/em\u003e, \u003cem\u003eC. ribicola\u003c/em\u003e). In their life cycle, these rusts infect alternate host plants, some of which are more rust resistant than others. We sprayed leaf extracts from resistant alternate host (\u003cem\u003eMelampyrum pratense\u003c/em\u003e, \u003cem\u003eImpatiens glandulifera\u003c/em\u003e, \u003cem\u003eVeronica chamaedrys\u003c/em\u003e,\u003cem\u003eRibes rubrum\u003c/em\u003e) and tested—both in the laboratory and on live plants—whether those extracts reduce rust spore production on plants that are normally easy to infect (\u003cem\u003eMelampyrum sylvaticum\u003c/em\u003e, \u003cem\u003eImpatiens balsamina\u003c/em\u003e, \u003cem\u003ePaeonia lactiflora\u003c/em\u003e, \u003cem\u003eRibes nigrum\u003c/em\u003e). Two commercial compounds, previously linked to rust resistance of alternate hosts to \u003cem\u003eCronartium\u003c/em\u003e rusts, a methanol control and an untreated control were also included to the experiment. Formation of rust uredinia and telia were estimated on the leaves after 6 weeks of incubation. In the laboratory, uredinia and telia of \u003cem\u003eC. pini\u003c/em\u003edeveloped most abundantly on \u003cem\u003ePaeonia lactiflora\u003c/em\u003e. Coverage of uredinia and telia did not differ between extracts on the leaves, but coverages of uredinia were significantly higher compared to dry control in the laboratory. In the greenhouse, infection percentage of leaves with uredinia and telia differed significantly among plant species but the treatments with extracts did not result in significant differences in infection percentage of the test plants. The results indicated that none of the tested extracts from rust-resistant alternate hosts and commercial compounds significantly inhibited fruiting and sporulation of \u003cem\u003eCronartium\u003c/em\u003e spp. on susceptible alternate hosts at medium (100 ppm) concentration.\u003c/p\u003e","manuscriptTitle":"Effect of leaf extracts on fruiting and sporulation of Cronartium pini and C. ribicola on susceptible alternate hosts","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-08 05:50:30","doi":"10.21203/rs.3.rs-8191801/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"08623a6b-6e52-489a-a579-36615fadcf13","owner":[],"postedDate":"December 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-02T02:58:08+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-08 05:50:30","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8191801","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8191801","identity":"rs-8191801","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}