Exploring and conserving genetic resources of corn salad: distribution and collecting of wild Valerianella spp. species in Poland

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Dostatny, Rob Treuren This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8397525/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Wild plant species represent a rich source of genetic variation and are therefore indispensable as a source of novel traits for crop improvement. Despite their importance crop wild relatives (CWR) are generally underrepresented in genetic resources collections. Here we performed an inventory of the CWR of corn salad ( Valerianella locusta ), a leafy vegetable that has increased in interest as food crop, and investigated their representation in genetic resources collections. In addition, we reported on the diversity collected for corn salad CWR during an expedition in Poland in 2024. Exploring the plant database Plants of the World Online, our inventory resulted in 79 CWR of which only 22 were represented in the genetic resources data repository Genesys. Focusing on the European distribution area resulted in 32 CWR of which only seven were included in Genesys with a total of 51 accessions. V. locusta occurs in the wild throughout Europe but only 15 accessions originating from only four European origin countries were encountered in Genesys. The collecting expedition covered most of Poland and resulted in 59 new accessions, including 54 of V. locusta , four of V. dentata and one of V. carinata . The expedition materials originated from a wide variety of habitat types and plant associations, while a large diversity in thousand-seed weight was observed among the accessions. It was concluded that CWR are poorly represented in current genetic resources collections of corn salad. The expedition was the first systematic collecting effort for corn salad CWR in a country and the collected materials greatly extend the genetic resources of corn salad available to the user community of gene bank collections. Biodiversity conservation corn salad crop wild relatives genetic resources habitat variation Poland seed collecting Valerianella Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 INTRODUCTION Our present-day crops once originated from wild plant species that were gradually adapted for cultivation and consumption through human activities. This domestication process caused a narrowing of the genetic variation that later was further reduced by modern plant breeding. The strong reduction of diversity in our crops is generally referred to as genetic erosion (van de Wouw et al. 2010). Crop plants often no longer resemble their wild predecessors phenotypically. Nevertheless, gene transfer from wild species to crop plants may still be possible, although species may vary in the level of interfertility with the crop. Such wild species are referred to as crop wild relatives (CWR). Based on their level of interfertility with the crop species CWR can be classified according to the gene pool concept of Harlan & de Wet (1971). Because data about interfertility are often lacking for wild species, a new concept based on taxonomic considerations was introduced (Maxted et al . 2006). According to this concept CWR are assigned to different taxon groups based on their taxonomic relationship with the crop species. In the absence of interfertility data taxa belonging to the same genus as the crop species, or even from related genera, are considered CWR. Plant breeding is about the development of new crop varieties in response to changed cultivation conditions or changed consumer demands, requiring a constant need for novel traits. Traditionally, the cultivated gene pool is used by breeders as the preferred source of new diversity. However, limited through genetic erosion, the new traits of interest are increasingly difficult to find in the cultivated gene pool. Because wild species harbour a much wider diversity than crop species plant breeders are more and more interested in CWR (Hajjar & Hodgkin 2007). CWR constitute rich reservoirs of resistances against biotic and abiotic stresses and therefore are regarded as indispensable genetic resources in the development of a more sustainable agriculture (Mammadov et al . 2018). Unfortunately, CWR are difficult to access by plant breeders as wild species are usually underrepresented in ex situ collections (Castañeda-Álvarez et al . 2016; Khoury et al . 2010). Also the in situ diversity of wild species is often difficult to access, while the continued survival of many species in nature is seriously threatened by various factors, including the effects of climate change (Dempewolf et al ., 2014). It is therefore crucial to improve the ex situ conservation of CWR in order to ensure proper access to the diversity that is needed for breeding resilient crop varieties and safeguarding global food security (Bohra et al . 2022). Corn salad ( Valerianella locusta (L.) Laterr.), also known as lamb’s lettuce, is a diploid (2n = 14), annual, autogamous species in the family Valerianaceae . Corn salad belongs to a highly variable group of crop plants that are cultivated for their edible leaves and that are collectively referred to as leafy vegetables (Van Treuren et al . 2012). Corn salad has become popular for consumption as a ready-to-eat salad or ingredient of salad mixtures (Ceglie et al . 2018). Corn salad leaves are generally appreciated for the soft texture, nutty flavour and nutritional value (Fontana et al . 2003), while positive effects have been reported regarding certain human diseases including diabetes, cardiovascular disorders and cancer (Ramos-Bueno et al . 2016). Corn salad is an economically important crop for Europe as it harbours the main production areas in the world. France is responsible for the largest global production with ~ 43,000 ton on ~ 8,000 ha in 2014 (Verdin et al . 2018), while corn salad is the third most important greenhouse vegetable in Germany (Muminovic et al . 2004). Breeding targets in corn salad include leaf characteristics such as shape and colour (Muminovic et al . 2004), tolerance to temperature stress (Hawrylak-Nowak et al . 2018), shelf life (Beghi et al. 2014), and resistance to pests and diseases, including Fusarium oxysporum (Gilardi et al . 2008), Acidovorax valerianellae (Gardan et al . 2003; Thiele et al . 2011) and Peronospora valerianellae (Pietrek & Zinkernagel 2002). Valerianella represents a large genus with the number of reported species ranging from 50 to 181 (Bell 2004; Hidalgo et al . 2004; Muminovic et al . 2004). However, the number of corn salad CWR remains to be determined as many synonyms and unplaced names are in use (POWO 2025). Phylogenetic studies within the genus Valerianella are scarce and have been carried out with a limited number of species (Bell 2007; Hidalgo et al . 2004, 2010; Muminovic et al . 2004). To date the genetic relationship with the crop species is unclear for most corn salad CWR. Successful crosses with cultivated corn salad have been reported only for wild V. locusta and V. carinata Loisel. (Muminovic et al . 2004). Crop improvement relies heavily on proper access to a wide diversity in genetic resources collections (Engels & Visser 2003). It has been indicated by breeding companies that only narrow genetic diversity is present in available genetic resources of corn salad (Muminovic et al. 2004). As since then no reporting of new expeditions could be found in the public domain this situation most likely still holds. Due to the absence of crossing barriers with the crop species, V. locusta occurring in the wild can be the considered the main CWR of cultivated corn salad. Europe forms the main part of the native distribution area of V. locusta and the species can be found in all European countries (POWO 2025). However, to the best of our knowledge systematic collecting of V. locusta in European countries has not been performed. Poland is located in the centre of the native distribution area of V. locusta and may therefore harbour a rich genetic diversity of the species. Moreover, other CWR of corn salad are currently found in Poland, including V. dentata (L.) Pollich and V. rimosa Bastard, as well as V. mixta (L.) Dufr. and V. carinata Loisel. that are considered ephemerophytes (POWO 2025; Tokarska-Guzik et al. 2012). Here, we present the results of an inventory of corn salad CWR and their availability in genetic resources collections. In addition, we report about the diversity in corn salad CWR collected during a recent expedition throughout Poland. Our general aim was to unlock information on corn salad CWR and to extend their genetic diversity in genetic resources collections. MATERIAL & METHODS Inventory of Valerianella species An overview was made of species of the genus Valerianella using taxonomic information from the database Plants of the World Online (POWO 2025). As many synonyms exist, accepted species names were also extracted from POWO as well as information about the geographic distribution of the species. Data on native distribution were recorded as ISO 3166-1 alpha-3 country codes (ISO 2025). Representation in genetic resources collections An inventory of the crop wild relatives of corn salad maintained in genetic resources collections was performed using the data portal Genesys (2025). Accession data were downloaded using the genus name Valerianella as filter. In addition, data of species from other genera were downloaded in case of synonymous names accepted by POWO. The data were further filtered using the value ‘wild’ and ‘natural’ for the passport descriptor ‘biological status’. The country of origin of an accession was recorded as well as its MLS status (ITPGRFA 2025), availability and the name of the holding institute. Collecting expedition An expedition for the collecting of wild relatives of corn salad in Poland was organized in cooperation between INHORT and CGN. The expedition was mainly directed to wild populations of V. locusta . Known populations were selected based on species observations published in iNaturalist (2024) and through consultation of Polish botanists for suitable sampling locations. Furthermore, previously unknown populations were identified during the expedition by exploring typical habitats of the species, such as river dikes. Geographical spread across Poland was taken into account as much as possible. The expedition covered most of Poland, except for the north-eastern part of the country where Valerianella species are known to be less abundant. The expedition was conducted from 19-29 May 2024. Populations of V. dentata were revisited for seed collecting in July 2024 because of later seed development compared to V. locusta . Prior to seed collecting the population area was explored and covered as much as possible during sampling. In case of large populations seeds were collected from at least 30 plants, but in other cases smaller sample sizes were accepted. Seeds from sampled plants were bulked per population. During the expedition geographic data were recorded about the collecting site as well as data on habitat type, population characteristics, phenology of the Valerianella species and the most abundant accompanying plant species. Collecting sites and representative plants at sampling locations were photo documented. All collected samples were entered into the database of the Regional Centre for Horticultural Biodiversity, which allowed for proper documentation and enabled following the origin of the material (Grin-global 2025). Following the expedition seed samples were cleaned and dried at INHORT and their seed weight was determined. Due to insufficient seeds of some samples the thousand-seed weight (TSW) was estimated by counting 3 replicates of 100 seeds, following the simplified method described by the International Seed Testing Association (ISTA 2018). For nine samples TSW values were not determined because of insufficient seeds for accurate measurement. For seed multiplication purposes, seeds from each of the samples were transferred to CGN under the Standard Material Transfer Agreement (SMTA) of the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA 2025). Data analysis To obtain more insight in the diversity among the visited sites of the collecting expedition the sampled locations were grouped into different habitat types based on field characteristics. Relationships between collecting sites were also investigated based on the most common associated species recorded during collecting. Absence/presence data of accompanying species were used to calculate similarity values between collecting sites, which served as input for the K-Means Clustering algorithm. The analysis was performed using the biodiversity indicators species richness, Shannon index and Simpson index, which allow for the assessment of both the abundance and evenness of species distribution in habitats. The data were transformed using the Hellinger method to enable hierarchical Ward clustering, grouping habitats based on similarity of species composition. The optimal number of clusters was selected using the silhouette index, which allowed for the visualisation of a dendrogram with coloured groups and the interpretation of the ecological structure of habitats (Magurran 2013; Podani 1990). To investigate associations among habitat type and TSW of seed samples, a correlation analysis and a Principal Component Analysis (PCA) was carried out. These analyses were conducted using Python (Python Software Foundation 2001) in the Google Collaboratory (Colab), a cloud platform that allows Python code to be executed directly in a web browser. Colab provides access to pre-installed Python libraries and supports integration with packages for data manipulation, statistical analysis, and visualisation (Halyal 2019). RESULTS CWR inventory Inventory of the genus Valerianella resulted in 187 species records, of which the majority were considered synonyms by POWO. When synonyms and unplaced names were disregarded, 79 species remained comprising 54 Valeriana , 23 Valerianella and two species from other genera (Suppl. Table 1). Valerianella species have their native distribution in Europe, Asia, and/or Africa, while species assigned to Valeriana may also be found in the Americas (Suppl. Table 2). V. locusta has its main distribution throughout Europe, while also occurring in the Caucasus area and north-west Africa. CWR availability Examination of Genesys resulted in 103 records with corn salad CWR, related to 22 (28%) of the 79 species (Suppl. Table 2). The largest collections of these genetic resources are maintained by the Millennium Seed Bank of the Royal Botanic Gardens Kew with 48 accessions, the Israel Gene Bank for Agricultural Crops of the Agricultural Research Organisation with 20 accessions, the federal gene bank of the Leibnitz Institute of Plant Genetics and Crop Plant Research with 10 accessions and CGN with 7 accessions (results not shown). Out of the 103 CWR accessions only 25 (24%) were documented in Genesys as included in the multilateral system of the International Treaty and only 22 (21%) as available (results not shown). Zooming in on corn salad CWR occurring in the European distribution area resulted in 32 species. Out of these species only seven were represented in Genesys comprising a total of 51 accessions (Table 1). Despite the importance of V. locusta for corn salad breeding and despite its main distribution in Europe, only 15 accessions from only four European origin countries are documented in Genesys. Regarding Poland only a single accession of V. dentata was documented in Genesys (Table 1). Seed collecting The expedition in Poland resulted in 59 new accessions, comprising 54 seed samples of V. locusta , four of V. dentata and one of V. carinata (Suppl. Table 3). The different Valerianella species share similar leaf and flower characteristics but can easily be distinguished based on seed morphology (Fig. 1). Collecting sites were located throughout Poland with the exception of the north-eastern part of the country (Fig. 2). In general, the populations were found in ruderal environments with an open vegetation structure. The elevation of the collecting sites ranged from 6 to 332 m a.s.l. and the sampling area from 0.25 to 4,000 m 2 . Estimated population sizes ranged from 1 to 10,000 plants and the number of sampled plants per population from 1 to 90 (38 on average). Genotypic variation was difficult to estimate in the field as only little phenotypic variation was observed and populations sometimes consisted of large patches of plants with possibly identical genotype. The phenology of the plants varied considerably between, and sometimes also within, populations. Most populations displayed mixed phenological stages, with plants bearing unripe, ripe, and shattered seeds, while others were still flowering or completely senescent. Accession details are available from Suppl. Table 3. Collecting site variation A total number of 185 accompanying plant species were recorded for the 59 sampled Valerianella populations. Species composition and other collecting site characteristics are presented in Suppl. Table 4. Based on field characteristics the collecting sites were grouped into six different habitat types (Fig. 3): River dike slopes . Sampling was performed from areas along river dikes with different angles of inclination. Such habitats are often embankments with grassy vegetation and are sunny, moderately dry and regularly mowed or grazed. These habitats were not very diverse and the most common observed species were Arrhenatherum elatius , Dactylis glomerata and Galium mollugo . Riverside, riparian and floodplain sites . Samples were collected from areas next to a river and from plain areas along rivers. These habitats are more diverse because they cover a large gradient of humidity due to temporal variation in water availability throughout the growing season. The most common observed species included Agrostis stolonifera, Alopecurus pratensis , Centaurea stoebe , Galium aparine , Galium mollugo , Ranunculus acris and Urtica dioica . Meadows and roadsides . Plants were harvested from the edges of meadows and roadsides of forest areas. Seeds were collected from meadow habitats located between small forest fragments, between copses, in clear-cuts, on road edges, in fresh meadows and herbaceous meadows, at the edges of forests and open areas such as pastures. In this combination of meadow, forest and ruderal vegetation a rich species diversity occurs. Among the observed species were Achillea millefolium , Arrhenatherum elatius , Campanula patula , Centaurea jacea , Hypericum perforatum , Knautia arvensis , Leucanthemum vulgare , Lotus corniculatus , Plantago lanceolata , Potentilla argentea and Veronica chamaedrys . Railway tracks . Samples were collected along the tracks with typical ruderal vegetation harbouring species such as Agrostis capillaris , Artemisia vulgaris , Chenopodium album , Matricaria discoidea , Papaver rhoeas , Rubus caesius , Saponaria officinalis , Stellaria media , Taraxacum officinalle , Trifolium arvense , Vicia hirsuta and Viola arvensis . Margins of agricultural fields . In this habitat type several field species were observed, including Arenaria serpyllifolia , Avena fatua , Centaurea cyanus , Convolvulus arvensis , Euphorbia exigua , Euphorbia helioscopia , Lithospermum arvense , Myosotis arvensis , Neslia paniculata , Stachys annua , Trifolium repens , Veronica persica and Vicia angustifolia . Tree orchards . Plants were sampled at the base of orchard trees and in the area surrounding the orchards. Despite a distance of approximately 15 km, the visited sites harboured similar species, including Capsella bursa-pastoris , Chenopodium album , Equisetum arvense , Erigeron canadensis , Lamium purpureum , Plantago major , Poa annua , Polygonum aviculare , Potentilla anserina , Senecio vulgaris , Taraxacum officinalis and Veronica persica . Cluster analysis of the collecting sites based on species composition resulted in 10 different groups (Fig. 4; Suppl. Table 4). G1 consisted only of samples collected along agricultural fields (habitat type 5) and included all V. dentata accessions. These environments harbour rich segetal and ruderal plant communities occurring in rendzina soils, characterized by species typical for these soils, such as Bupleurum rotundifolium , Caucalis daucoides , Neslia paniculata , Ranunculus arvensis , Stachys annua and Thymelaea passerina . G2 comprised meadows and roadsides and orchard habitats (type 3 and 6) and G3 mainly areas along railway tracks and along agricultural fields (type 4 and 5). G1-G3 together formed a major cluster, characterized by a large diversity of associated species observed at the collecting sites. The second major cluster is divided in two subclusters, respectively consisting of G4-G7 and G8-G10. G4 included only riparian and floodplain sites (habitat type 2) and showed a poor species diversity, while G5-G7 each consisted of combinations of habitat types (respectively 1, 2, 3 and 5; 1, 3 and 5; 1 and 3) and were found to be more divers in species composition. Nearly all collecting sites included in G5-G7 shared the species Plantago lanceolata , Poa annua and Potentilla argentea . Also each of G8-G10 was constituted by combinations of habitat types. G8 included types 1, 2, 3 and 4 and G9 types 1, 3, 4 and 5, which represented the highest species diversity of all collecting sites. G10 was formed by types 1, 2, 3 and 5, including a great share of grasses, as well as Rumex crispus . Arrhenatherum elatius occurred in groups G8-G10 and was shared by all sampled sites. Seed characteristics TSW values of the collected seed samples varied among the collecting sites and differed markedly between habitat types (Suppl. Table 4). Lowest values were found for river dike slopes (habitat type 1) and floodplain sites (type 2). Meadows and roadsides (type 3) and railway tracks (type 4) showed intermediate TSW, while the highest values were observed for margins of agricultural fields (type 5) and orchards (type 6). All V. dentata samples originated from margins of agricultural fields and showed relatively high TSW, likewise the V . locusta samples collected from this habitat type (Fig. 5). Analysis of variance (ANOVA) revealed a significant effect of habitat on TSW (F₅,₄₅ = 33.55, p < 0.0001). Tukey HSD post hoc tests showed that habitats 5 and 6 had the highest TSW values and did not differ from each other, whereas habitat 1 had the lowest TSW values. Habitats 2, 3, and 4 showed intermediate values, partially overlapping with the values from the other habitats. TSW was found to be positively correlated (r = 0.47, p < 0.001) with the altitude of the collecting site (Fig. 5). As habitat type and altitude of the collecting site do not represent completely independent variables, a PCA was carried out to identify the site characteristics that contribute most to the observed variation in TSW (Fig. 6). The first principal component, accounting for 73.2% of the variation was composed of TSW value (r = 0.94, p < 0.001) and habitat type (r = 0.92, p < 0.001). The second principal component, explaining 21.6% of the variation, was ascribed to altitude (r = 0.73, p < 0.001). Thus habitat type had a stronger effect on TSW than altitude. DISCUSSION CWR taxonomy Various concepts are in use to determine which wild plant species can be considered relatives of a crop species. The gene pool concept is probably the most practical for plant breeders as it is based on the ability to transfer genes from wild species to a crop (Harlan & de Wet 1971). According to this concept species are assigned to the primary gene pool in case of interfertility, to the secondary gene pool in case of limited interfertility and to the tertiary gene pool when special techniques are required such as embryo rescue and bridge crosses. In this sense wild V. locusta can be considered a primary gene pool species of cultivated corn salad. The use of the gene pool concept for corn salad is complicated by the fact that interfertility data for wild species are usually lacking for understudied crops. Alternatively, existing taxonomic hierarchy may be used as a proxy for CWR relatedness with the cultivated crop (Maxted et al . 2006). According to this concept wild V. locusta can be assigned to taxon group 1, while species with missing crossing information but belonging to same genus as the crop are assigned to taxon group 4. In the present study we used the botanical name Valerianella locusta as the basis for our inventory of corn salad CWR and summarized all species sharing the same genus name. As the crop species has recently been reassigned to the genus Valeriana (POWO 2025) it can be argued that our CWR survey should have focussed on this genus. Valeriana represents the biggest genus within the Valerianaceae , comprising 446 accepted species names (POWO 2025). The 54 Valeriana species that previously were assigned to the genus Valerianella were addressed as corn salad CWR in our survey (Suppl. Table 2). The CWR status is less straightforward for the additional 392 Valeriana species, of which 337 (86%) have their native distribution outside Europe (Suppl. Table 5). Their genetic relationship with cultivated corn salad may be low as the crop species originated from Europe (Péron & Rees 1998). Moreover, a molecular study using several representatives of the genera belonging to the Valerianaceae revealed a separate, relatively homogeneous, group of Valerianella locusta and the nine other investigated congeneric species within the phylogenetic tree (Hidalgo et al . 2010). Therefore, for most Valeriana species the CWR status and usefulness for corn salad breeding remains to be determined. CWR accessibility Ensuring proper access to the genetic resources maintained in crop collections is one of the main responsibilities of gene banks in order to link conservation with utilization (Engels & Visser 2003). Despite their importance for crop improvement, CWR generally show limited representation in genetic resources collections (Castañeda-Álvarez et al . 2016; Khoury et al . 2010). Sufficient budget needs to be available to cover the expenses related to a collecting expedition, which can be considerable in case of faraway distribution areas. In addition, ex situ maintenance of wild species can be a burden to gene bank curators because regeneration may be laborious, often requiring specific expertise for germination, flowering and seed production. Moreover, legislation regarding access and benefit sharing of genetic resources has become more and more stricter over the years, often requiring time-consuming administrative processes with the host country, if successful at all (EU 2025). In addition to representation in genetic resources collections, availability of seed samples for utilization forms another issue regarding access to CWR. It has been shown that poor collection accessibility is mainly due to regeneration backlogs causing insufficient quantity and quality of seed stocks for distribution and utilization (Khoury et al . 2010). Approximately half of the 103 accessions of corn salad CWR documented in Genesys are conserved by the Millennium Seed Bank Kew that only supplies seeds for non-commercial purposes (MSB 2025). With 20 accessions documented in Genesys, the Israeli gene bank is the second largest maintainer of corn salad CWR, but accession availability can be questioned as no seed requesting procedures or conditions could be found on the institutional website (IGB 2025). Thus, the breeding industry has only poor access to corn salad CWR for crop improvement purposes. The quality and quantity of plant seeds collected in the wild are usually insufficient for direct long-term ex situ conservation and distribution to users. It is therefore common practice that newly collected seeds first enter a seed multiplication programme. The seeds of the corn salad CWR collected during the expedition in Poland are planned by CGN for regeneration in the Netherlands in 2026 following the protocols available from their website (CGN 2025). Successfully regenerated accessions will then be included in the collections of CGN and INHORT and documented in their institutional databases as well as in the EURISCO catalogue (ECPGR 2025). Seed samples will be made available for distribution to the user community under the Standard Material Transfer Agreement (SMTA) of the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA 2025). Diversity survey The general aim of gene banks is to develop collections representing the genetic diversity of a crop gene pool as much as possible with a minimum level of redundancy (Frankel & Brown 1984). Poland is located in the centre of the European distribution area of wild V. locusta and is therefore expected to harbour a rich diversity for this corn salad CWR. This diversity was sampled as wide as possible during our expedition by collecting seeds from a wide eco-geographic range. V. locusta is characterised by the following ecological habitat indicators: i. light index L5, i.e. full light; ii. thermal index T4-5, i.e. moderately warm climatic conditions; iii. soil moisture index W3-2, i.e. dry or fresh; iv. soil or water acidity index R4, i.e. neutral soil (6 < = pH < 7); v. soil granulometric index D3-4, i.e. sand or sandy loam and silty formations and vi. organic matter content index H2, i.e. mineral-humus soil (Zarzycki et al. 2002). These indicators clearly reflect the plasticity of V. locusta and point towards a strong adaptative capacity, enabling the species to occur and survive in various habitats and in different associations of plant communities. The large variation in habitat types and species composition observed for the collecting sites in the present study was in line with this presumed plasticity. Accession PolVal24-037 was found to be particularly interesting because it was collected from the crevices of a stone wall along a side walk. The ability of V. locusta to survive and reproduce under these extremely unfavourable habitat conditions indicates a high tolerance to abiotic stress and the ability to adapt to limited resources, such as minimal soil content and restricted water availability. Habitats are considered to be strongly linked with species (Bunce et al . 2013). The Valerianella samples were collected from a wide range of habitat types and plant associations, but a hierarchical cluster analysis did not reveal a clear relationship between these population parameters. Habitat classification was based primarily on their spatial distribution and ecological characteristics, such as environmental conditions, structure, and location. Species occurring in each habitat were considered as supplementary information supporting the classification. Consequently, plant species were not strictly grouped by habitat type, as species characteristic for a given habitat were not always present. Furthermore, species were recorded that were most abundant at a collection site, while less common species were disregarded. Therefore, the data reflect common habitat characteristics rather than a complete floristic inventory. The classification was based on EUNIS Habitat Classification (Chytrý et al. 2020) and a combination of others modeling strategies (Ferrier & Guisan 2006). TSW values of the collected Valerianella samples varied markedly among the habitat types of the origin site. Variation in TSW between different habitats may result from a plastic phenotypic response and/or from genetic differences between populations. Phenotypic plasticity in seed mass, often expressed as TSW, is a commonly observed mechanism by which individual genotypes can modify their investment in offspring size and mass in response to environmental conditions (Gnan et al. 2014; Razzaque & Juenger 2022). Mechanisms that determine the increase or decrease in seed mass in more challenging habitats include, among others, limited plant resources such as water and nutrients, thermal stress, and a shortened growing season. In response to these factors, plants may increase individual seed mass, i.e. the so-called "quality over quantity" strategy, which improves seedling survival in harsh conditions, or reduce seed mass and increase seed number, i.e. the "bet-hedging" strategy (Marinoni et al. 2022). From an ecological and biogeographic perspective, observed seed mass gradients, e.g. with altitude, rainfall or soil type, are well documented (Zhao et al. 2022). Tracking this variation allows us to understand how populations respond to local conditions and which populations may represent a valuable source of tolerance traits for breeding programs (Veselá et al. 2020). The specific microhabitat in which PolVal24-037 persisted, demonstrated the high degree of plasticity of V. locusta , including tolerance to drought stress, nutrient deficiencies and temperature fluctuations. Resistances to abiotic stress are valuable traits in response to changing environmental conditions, such as caused by climate change, and are of great importance in breeding improved crop varieties. Proper access to the wide diversity of CWR is therefore indispensable for a sustainable agriculture and to ensure food security (Dostatny & Dajdok 2020; Vincent et al. 2013). Concluding remarks Crop improvement increasingly depends on proper access to the wide genetic diversity contained in their CWR. The CWR of corn salad are characterised by poor representation in current genetic resources collections and limited availability to the breeding industry. The collecting expedition carried out in Poland in 2024 is the first comprehensive collecting activity for corn salad CWR in a country. The expedition materials comprise a rich diversity and greatly extend the genetic resources of corn salad available, not only to plant breeders, but to other users of gene bank collections as well. To further strengthen ex situ collections of corn salad it is recommended that V. locusta is systematically sampled from other parts of its distribution area. Other potentially interesting corn salad CWR can be collected as bycatch during expeditions and explored for their usefulness in crop improvement. Declarations Conflicts of Interest The authors declare no conflicts of interest. Funding This work was supported by the targeted grants of the Ministry of Agriculture and Rural Development in 2024 in accordance with grant agreement no. DHR.bz.070.1.2024 for the Institute of Horticulture-National Research Institute, signed on 30 April 2024 (author D.F.D.) Author Contribution D.F.D: Collection (inventory), conceptualization, original draft preparation, methodology, data counting and analysis, writing. R.V.T: Collection (inventory), conceptualization, methodology, data gathering, writing. All authors reviewed the manuscript. Acknowledgement The authors are grateful to Wojciech Szymański, Zygmunt Dajdok and Karol Bubel for their help in the collecting activities. Data Availability All data supporting the findings of this study are available within the paper and its Supplementary Information. References Beghia R, Giovenzanaa V, Civellia R, Malegorib C, Burattib S, et al . 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14:35:38","extension":"png","order_by":25,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":39505,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineArticleCWRValerianellafigure6.png","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/f88eca249b6b21bc649a5f63.png"},{"id":99812111,"identity":"46ae872f-2eb9-447a-b1b6-98a81f6cecb1","added_by":"auto","created_at":"2026-01-08 14:36:00","extension":"png","order_by":26,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":710748,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/9a6200b59a845ef57a4849bb.png"},{"id":99811926,"identity":"6cad1a1d-c96c-45a2-b403-8ee30b7bef63","added_by":"auto","created_at":"2026-01-08 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14:35:36","extension":"png","order_by":29,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":275427,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/38518cfc517536285af89b6b.png"},{"id":99812089,"identity":"9df27ec4-f37b-416c-b55d-5e2ade16bb3b","added_by":"auto","created_at":"2026-01-08 14:35:53","extension":"png","order_by":30,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":260267,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/8c1b8590a1c2abe64997044f.png"},{"id":99812106,"identity":"f4522772-91ee-49be-a364-70aa989a07af","added_by":"auto","created_at":"2026-01-08 14:35:59","extension":"png","order_by":31,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":235342,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/f08552162727c10ab64bfe25.png"},{"id":99811992,"identity":"b51566bb-b926-40f1-b8f7-917a4f702385","added_by":"auto","created_at":"2026-01-08 14:35:24","extension":"png","order_by":32,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":226711,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/d07726560e5613fa2ab1a8fa.png"},{"id":99812203,"identity":"02c94ae3-64d8-4dec-8dce-571a61b8b4a6","added_by":"auto","created_at":"2026-01-08 14:36:27","extension":"xml","order_by":33,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":103674,"visible":true,"origin":"","legend":"","description":"","filename":"79aa7055602749238d3858eb16529cc01structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/b9233f49b71010242b42014b.xml"},{"id":99812037,"identity":"251659b9-715d-4926-9e2d-3fc6be5bead1","added_by":"auto","created_at":"2026-01-08 14:35:37","extension":"html","order_by":34,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":120758,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/6e4e09d895c96cadccedbc89.html"},{"id":99812178,"identity":"2a08cdb3-c579-45e9-934f-b0ce41853d8c","added_by":"auto","created_at":"2026-01-08 14:36:25","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":647142,"visible":true,"origin":"","legend":"\u003cp\u003eSeed morphology of the three \u003cem\u003eValerianella\u003c/em\u003especies sampled during the collecting expedition in Poland in 2024.\u003c/p\u003e","description":"","filename":"ArticleCWRValerianellafigure1.png","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/c38044738900ec8d4c158e76.png"},{"id":99812150,"identity":"181acd44-2b58-4336-bc08-288825505b24","added_by":"auto","created_at":"2026-01-08 14:36:19","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":102573,"visible":true,"origin":"","legend":"\u003cp\u003eGeographic origin of the \u003cem\u003eValerianella\u003c/em\u003e accessions collected in Poland in 2024. The map was prepared with Google Maps. The numbers in the map correspond to the sample codes presented in Suppl. Table 3.\u003c/p\u003e","description":"","filename":"ArticleCWRValerianellafigure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/24ee2f8d68fb2a1f2ccf22a1.jpg"},{"id":99812134,"identity":"e94e157f-0e0c-4ba8-9bfe-8246b94c630d","added_by":"auto","created_at":"2026-01-08 14:36:10","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1160667,"visible":true,"origin":"","legend":"\u003cp\u003eHabitat types of the visited collecting sites in Poland in 2024 with sample code presented between brackets.\u003c/p\u003e","description":"","filename":"ArticleCWRValerianellafigure3.png","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/0fe12c05d3fb5079b4ea07d1.png"},{"id":99812103,"identity":"da8176f9-abcd-4c1b-a41a-ab1213209d52","added_by":"auto","created_at":"2026-01-08 14:35:57","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":86798,"visible":true,"origin":"","legend":"\u003cp\u003eCluster analysis of the \u003cem\u003eValerianella\u003c/em\u003ecollecting sites based on the most abundant accompanying species. The collecting sites are denoted by sample code on the x-axis. The identified clusters are marked in different colour and are denoted by G1 to G10 and in brackets are written the six habitat types as described in the results.\u003c/p\u003e","description":"","filename":"ArticleCWRValerianellafigure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/182fa66a0fb7b37de8f26f46.jpg"},{"id":99812140,"identity":"7e5df684-700c-4c19-9000-1d6a9607b7a7","added_by":"auto","created_at":"2026-01-08 14:36:12","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":104903,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between thousand-seed weight (TSW) and altitude (meters above sea level) of the collecting site for the sampled \u003cem\u003eV. locusta \u003c/em\u003eand \u003cem\u003eV. dentata\u003c/em\u003e populations.\u003cstrong\u003e \u003c/strong\u003eDetails of the linear regression analysis are presented at the top of the figure. Ellipses have been added for the six habitat types, illustrating the variation in thousand-seed weight (TSW) between populations.\u003c/p\u003e","description":"","filename":"ArticleCWRValerianellafigure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/8bf7f8875fda9cfa494e30b6.jpg"},{"id":99811973,"identity":"685c0afd-ad97-4228-b70a-51da18817160","added_by":"auto","created_at":"2026-01-08 14:35:20","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":73730,"visible":true,"origin":"","legend":"\u003cp\u003ePrincipal Component Analysis (PCA) plot of thousand-seed weight (TSW) and collecting site data of the collected \u003cem\u003eV. locusta\u003c/em\u003e and \u003cem\u003eV. dentata\u003c/em\u003eseed samples. The percentage variation explained by the first two principal components is presented between brackets in the axis legends.\u003c/p\u003e","description":"","filename":"ArticleCWRValerianellafigure6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/681254259be85e3582641c63.jpg"},{"id":100376778,"identity":"25381a69-2983-494d-885e-c08a96bca25e","added_by":"auto","created_at":"2026-01-16 08:45:48","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2980125,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/c4fc7dcb-1866-4984-8ce0-d2ad31b8fa1c.pdf"},{"id":99812143,"identity":"ba4521c0-f703-4be8-8857-cd197c651c37","added_by":"auto","created_at":"2026-01-08 14:36:17","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":68897,"visible":true,"origin":"","legend":"","description":"","filename":"ArticleCWRValerianellasuppl.tables.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/60f07982955ee0e380020efd.xlsx"},{"id":99811991,"identity":"a87c2dac-55bc-49b6-984a-1cc6fcd52a0e","added_by":"auto","created_at":"2026-01-08 14:35:23","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":21498,"visible":true,"origin":"","legend":"","description":"","filename":"ArticleCWRValerianellatable1.docx","url":"https://assets-eu.researchsquare.com/files/rs-8397525/v1/56828cfc5f285fd1de042572.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Exploring and conserving genetic resources of corn salad: distribution and collecting of wild Valerianella spp. species in Poland","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eOur present-day crops once originated from wild plant species that were gradually adapted for cultivation and consumption through human activities. This domestication process caused a narrowing of the genetic variation that later was further reduced by modern plant breeding. The strong reduction of diversity in our crops is generally referred to as genetic erosion (van de Wouw \u003cem\u003eet al.\u003c/em\u003e 2010). Crop plants often no longer resemble their wild predecessors phenotypically. Nevertheless, gene transfer from wild species to crop plants may still be possible, although species may vary in the level of interfertility with the crop. Such wild species are referred to as crop wild relatives (CWR). Based on their level of interfertility with the crop species CWR can be classified according to the gene pool concept of Harlan \u0026amp; de Wet (1971). Because data about interfertility are often lacking for wild species, a new concept based on taxonomic considerations was introduced (Maxted \u003cem\u003eet al\u003c/em\u003e. 2006). According to this concept CWR are assigned to different taxon groups based on their taxonomic relationship with the crop species. In the absence of interfertility data taxa belonging to the same genus as the crop species, or even from related genera, are considered CWR.\u003c/p\u003e \u003cp\u003ePlant breeding is about the development of new crop varieties in response to changed cultivation conditions or changed consumer demands, requiring a constant need for novel traits. Traditionally, the cultivated gene pool is used by breeders as the preferred source of new diversity. However, limited through genetic erosion, the new traits of interest are increasingly difficult to find in the cultivated gene pool. Because wild species harbour a much wider diversity than crop species plant breeders are more and more interested in CWR (Hajjar \u0026amp; Hodgkin 2007). CWR constitute rich reservoirs of resistances against biotic and abiotic stresses and therefore are regarded as indispensable genetic resources in the development of a more sustainable agriculture (Mammadov \u003cem\u003eet al\u003c/em\u003e. 2018). Unfortunately, CWR are difficult to access by plant breeders as wild species are usually underrepresented in \u003cem\u003eex situ\u003c/em\u003e collections (Casta\u0026ntilde;eda-\u0026Aacute;lvarez \u003cem\u003eet al\u003c/em\u003e. 2016; Khoury \u003cem\u003eet al\u003c/em\u003e. 2010). Also the \u003cem\u003ein situ\u003c/em\u003e diversity of wild species is often difficult to access, while the continued survival of many species in nature is seriously threatened by various factors, including the effects of climate change (Dempewolf \u003cem\u003eet al\u003c/em\u003e., 2014). It is therefore crucial to improve the \u003cem\u003eex situ\u003c/em\u003e conservation of CWR in order to ensure proper access to the diversity that is needed for breeding resilient crop varieties and safeguarding global food security (Bohra \u003cem\u003eet al\u003c/em\u003e. 2022).\u003c/p\u003e \u003cp\u003eCorn salad (\u003cem\u003eValerianella locusta\u003c/em\u003e (L.) Laterr.), also known as lamb\u0026rsquo;s lettuce, is a diploid (2n\u0026thinsp;=\u0026thinsp;14), annual, autogamous species in the family \u003cem\u003eValerianaceae\u003c/em\u003e. Corn salad belongs to a highly variable group of crop plants that are cultivated for their edible leaves and that are collectively referred to as leafy vegetables (Van Treuren \u003cem\u003eet al\u003c/em\u003e. 2012). Corn salad has become popular for consumption as a ready-to-eat salad or ingredient of salad mixtures (Ceglie \u003cem\u003eet al\u003c/em\u003e. 2018). Corn salad leaves are generally appreciated for the soft texture, nutty flavour and nutritional value (Fontana \u003cem\u003eet al\u003c/em\u003e. 2003), while positive effects have been reported regarding certain human diseases including diabetes, cardiovascular disorders and cancer (Ramos-Bueno \u003cem\u003eet al\u003c/em\u003e. 2016). Corn salad is an economically important crop for Europe as it harbours the main production areas in the world. France is responsible for the largest global production with ~\u0026thinsp;43,000 ton on ~\u0026thinsp;8,000 ha in 2014 (Verdin \u003cem\u003eet al\u003c/em\u003e. 2018), while corn salad is the third most important greenhouse vegetable in Germany (Muminovic \u003cem\u003eet al\u003c/em\u003e. 2004). Breeding targets in corn salad include leaf characteristics such as shape and colour (Muminovic \u003cem\u003eet al\u003c/em\u003e. 2004), tolerance to temperature stress (Hawrylak-Nowak \u003cem\u003eet al\u003c/em\u003e. 2018), shelf life (Beghi \u003cem\u003eet al.\u003c/em\u003e 2014), and resistance to pests and diseases, including \u003cem\u003eFusarium oxysporum\u003c/em\u003e (Gilardi \u003cem\u003eet al\u003c/em\u003e. 2008), \u003cem\u003eAcidovorax valerianellae\u003c/em\u003e (Gardan \u003cem\u003eet al\u003c/em\u003e. 2003; Thiele \u003cem\u003eet al\u003c/em\u003e. 2011) and \u003cem\u003ePeronospora valerianellae\u003c/em\u003e (Pietrek \u0026amp; Zinkernagel 2002).\u003c/p\u003e \u003cp\u003e \u003cem\u003eValerianella\u003c/em\u003e represents a large genus with the number of reported species ranging from 50 to 181 (Bell 2004; Hidalgo \u003cem\u003eet al\u003c/em\u003e. 2004; Muminovic \u003cem\u003eet al\u003c/em\u003e. 2004). However, the number of corn salad CWR remains to be determined as many synonyms and unplaced names are in use (POWO 2025). Phylogenetic studies within the genus \u003cem\u003eValerianella\u003c/em\u003e are scarce and have been carried out with a limited number of species (Bell 2007; Hidalgo \u003cem\u003eet al\u003c/em\u003e. 2004, 2010; Muminovic \u003cem\u003eet al\u003c/em\u003e. 2004). To date the genetic relationship with the crop species is unclear for most corn salad CWR. Successful crosses with cultivated corn salad have been reported only for wild \u003cem\u003eV. locusta\u003c/em\u003e and \u003cem\u003eV. carinata\u003c/em\u003e Loisel. (Muminovic \u003cem\u003eet al\u003c/em\u003e. 2004). Crop improvement relies heavily on proper access to a wide diversity in genetic resources collections (Engels \u0026amp; Visser 2003). It has been indicated by breeding companies that only narrow genetic diversity is present in available genetic resources of corn salad (Muminovic et al. 2004). As since then no reporting of new expeditions could be found in the public domain this situation most likely still holds.\u003c/p\u003e \u003cp\u003eDue to the absence of crossing barriers with the crop species, \u003cem\u003eV. locusta\u003c/em\u003e occurring in the wild can be the considered the main CWR of cultivated corn salad. Europe forms the main part of the native distribution area of \u003cem\u003eV. locusta\u003c/em\u003e and the species can be found in all European countries (POWO 2025). However, to the best of our knowledge systematic collecting of \u003cem\u003eV. locusta\u003c/em\u003e in European countries has not been performed. Poland is located in the centre of the native distribution area of \u003cem\u003eV. locusta\u003c/em\u003e and may therefore harbour a rich genetic diversity of the species. Moreover, other CWR of corn salad are currently found in Poland, including \u003cem\u003eV. dentata\u003c/em\u003e (L.) Pollich and \u003cem\u003eV. rimosa\u003c/em\u003e Bastard, as well as \u003cem\u003eV. mixta\u003c/em\u003e (L.) Dufr. and \u003cem\u003eV. carinata\u003c/em\u003e Loisel. that are considered ephemerophytes (POWO 2025; Tokarska-Guzik \u003cem\u003eet al.\u003c/em\u003e 2012). Here, we present the results of an inventory of corn salad CWR and their availability in genetic resources collections. In addition, we report about the diversity in corn salad CWR collected during a recent expedition throughout Poland. Our general aim was to unlock information on corn salad CWR and to extend their genetic diversity in genetic resources collections.\u003c/p\u003e"},{"header":"MATERIAL \u0026 METHODS","content":"\u003cp\u003e\u003cstrong\u003eInventory of \u003cem\u003eValerianella\u003c/em\u003e species\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAn overview was made of species of the genus \u003cem\u003eValerianella\u003c/em\u003e using taxonomic information from the database Plants of the World Online (POWO 2025). As many synonyms exist, accepted species names were also extracted from POWO as well as information about the geographic distribution of the species. Data on native distribution were recorded as ISO 3166-1 alpha-3 country codes (ISO 2025).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRepresentation in genetic resources collections\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAn inventory of the crop wild relatives of corn salad maintained in genetic resources collections was performed using the data portal Genesys (2025). Accession data were downloaded using the genus name \u003cem\u003eValerianella\u003c/em\u003e as filter. In addition, data of species from other genera were downloaded in case of synonymous names accepted by POWO. The data were further filtered using the value \u0026lsquo;wild\u0026rsquo; and \u0026lsquo;natural\u0026rsquo; for the passport descriptor \u0026lsquo;biological status\u0026rsquo;. The country of origin of an accession was recorded as well as its MLS status (ITPGRFA 2025), availability and the name of the holding institute.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCollecting expedition\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAn expedition for the collecting of wild relatives of corn salad in Poland was organized in cooperation between INHORT and CGN. The expedition was mainly directed to wild populations of \u003cem\u003eV. locusta\u003c/em\u003e. Known populations were selected based on species observations published in iNaturalist (2024) and through consultation of Polish botanists for suitable sampling locations. Furthermore, previously unknown populations were identified during the expedition by exploring typical habitats of the species, such as river dikes. Geographical spread across Poland was taken into account as much as possible. The expedition covered most of Poland, except for the north-eastern part of the country where \u003cem\u003eValerianella\u003c/em\u003e species are known to be less abundant. The expedition was conducted from 19-29 May 2024. Populations of \u003cem\u003eV. dentata\u003c/em\u003e were revisited for seed collecting in July 2024 because of later seed development compared to \u003cem\u003eV. locusta\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003ePrior to seed collecting the population area was explored and covered as much as possible during sampling. In case of large populations seeds were collected from at least 30 plants, but in other cases smaller sample sizes were accepted. Seeds from sampled plants were bulked per population. During the expedition geographic data were recorded about the collecting site as well as data on habitat type, population characteristics, phenology of the \u003cem\u003eValerianella\u003c/em\u003e species and the most abundant accompanying plant species. Collecting sites and \u0026nbsp;representative plants at sampling locations were photo documented. All collected samples were entered into the database of the Regional Centre for Horticultural Biodiversity, which allowed for proper documentation and enabled following the origin of the material (Grin-global 2025).\u003c/p\u003e\n\u003cp\u003eFollowing the expedition seed samples were cleaned and dried at INHORT and their seed weight was determined. Due to insufficient seeds of some samples the thousand-seed weight (TSW) was estimated by counting 3 replicates of 100 seeds, following the simplified method described by the International Seed Testing Association (ISTA 2018). For nine samples TSW values were not determined because of insufficient seeds for accurate measurement. For seed multiplication purposes, seeds from each of the samples were transferred to CGN under the Standard Material Transfer Agreement (SMTA) of the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA 2025). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo obtain more insight in the diversity among the visited sites of the collecting expedition the sampled locations were grouped into different habitat types based on field characteristics. Relationships between collecting sites were also investigated based on the most common associated species recorded during collecting. Absence/presence data of accompanying species were used to calculate similarity values between collecting sites, which served \u0026nbsp;as input for the K-Means Clustering algorithm. The analysis was performed using the biodiversity indicators species richness, Shannon index and Simpson index, which allow for the assessment of both the abundance and evenness of species distribution in habitats. The data were transformed using the Hellinger method to enable hierarchical Ward clustering, grouping habitats based on similarity of species composition. The optimal number of clusters was selected using the silhouette index, which allowed for the visualisation of a dendrogram with coloured groups and the interpretation of the ecological structure of habitats (Magurran 2013; Podani 1990). To investigate associations among habitat type and TSW of seed samples, a correlation analysis and a Principal Component Analysis (PCA) was carried out. These analyses were conducted using Python (Python Software Foundation 2001) in the Google Collaboratory (Colab), a cloud platform that allows Python code to be executed directly in a web browser. Colab provides access to pre-installed Python libraries and supports integration with packages for data manipulation, statistical analysis, and visualisation (Halyal 2019).\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cp\u003e\u003cstrong\u003eCWR inventory\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInventory of the genus \u003cem\u003eValerianella\u003c/em\u003e resulted in 187 species records, of which the majority were considered synonyms by POWO. When synonyms and unplaced names were disregarded, 79 species remained comprising 54 \u003cem\u003eValeriana\u003c/em\u003e, 23 \u003cem\u003eValerianella\u003c/em\u003e and two species from other genera (Suppl. Table 1). \u003cem\u003eValerianella\u003c/em\u003e species have their native distribution in Europe, Asia, and/or Africa, while species assigned to \u003cem\u003eValeriana\u003c/em\u003e may also be found in the Americas (Suppl. Table 2). \u003cem\u003eV. locusta\u003c/em\u003e has its main distribution throughout Europe, while also occurring in the Caucasus area and north-west Africa. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCWR availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eExamination of Genesys resulted in 103 records with corn salad CWR, related to 22 (28%) of the 79 species (Suppl. Table 2). The largest collections of these genetic resources are maintained by the Millennium Seed Bank of the Royal Botanic Gardens Kew with 48 accessions, the Israel Gene Bank for Agricultural Crops of the Agricultural Research Organisation with 20 accessions, the federal gene bank of the Leibnitz Institute of Plant Genetics and Crop Plant Research with 10 accessions and CGN with 7 accessions (results not shown). Out of the 103 CWR accessions only 25 (24%) were documented in Genesys as included in the multilateral system of the International Treaty and only 22 (21%) as available (results not shown).\u003c/p\u003e\n\u003cp\u003eZooming in on corn salad CWR occurring in the European distribution area resulted in 32 species. Out of these species only seven were represented in Genesys comprising a total of 51 accessions (Table 1). Despite the importance of \u003cem\u003eV. locusta\u003c/em\u003e for corn salad breeding and despite its main distribution in Europe, only 15 accessions from only four European origin countries are documented in Genesys. Regarding Poland only a single accession of \u003cem\u003eV. dentata\u003c/em\u003e was documented in Genesys (Table 1).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSeed collecting\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe expedition in Poland resulted in 59 new accessions, comprising 54 seed samples of \u0026nbsp;\u003cem\u003eV. locusta\u003c/em\u003e, four of \u003cem\u003eV. dentata\u003c/em\u003e and one of \u003cem\u003eV. carinata\u003c/em\u003e (Suppl. Table 3). The different \u003cem\u003eValerianella\u003c/em\u003e species share similar leaf and flower characteristics but can easily be distinguished based on seed morphology (Fig. 1). Collecting sites were located throughout Poland with the exception of the north-eastern part of the country (Fig. 2). In general, the populations were found in ruderal environments with an open vegetation structure. The elevation of the collecting sites ranged from 6 to 332 m a.s.l. and the sampling area from 0.25 to 4,000 m\u003csup\u003e2\u003c/sup\u003e. Estimated population sizes ranged from 1 to 10,000 plants and the number of sampled plants per population from 1 to 90 (38 on average). Genotypic variation was difficult to estimate in the field as only little phenotypic variation was observed and populations sometimes consisted of large patches of plants with possibly identical genotype. The phenology of the plants varied considerably between, and sometimes also within, populations. Most populations displayed mixed phenological stages, with plants bearing unripe, ripe, and shattered seeds, while others were still flowering or completely senescent. Accession details are available from Suppl. Table 3.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCollecting site variation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total number of 185 accompanying plant species were recorded for the 59 sampled \u003cem\u003eValerianella\u003c/em\u003e populations. Species composition and other collecting site characteristics are presented \u0026nbsp;in Suppl. Table 4. Based on field characteristics the collecting sites were grouped into six different habitat types (Fig. 3):\u003c/p\u003e\n\u003col class=\"decimal_type\"\u003e\n \u003cli\u003e\u003cem\u003eRiver dike slopes\u003c/em\u003e. Sampling was performed from areas along river dikes with different angles of inclination. Such habitats are often embankments with \u0026nbsp; grassy vegetation and are sunny, moderately dry and regularly mowed or grazed. These habitats were not very diverse and the most common observed species were \u003cem\u003eArrhenatherum elatius\u003c/em\u003e, \u003cem\u003eDactylis glomerata\u003c/em\u003e and \u003cem\u003eGalium mollugo\u003c/em\u003e.\u003c/li\u003e\n \u003cli\u003e\u003cem\u003eRiverside, riparian and floodplain sites\u003c/em\u003e. Samples were collected from areas next to a river and from plain areas along rivers. These habitats are more diverse because they cover a large gradient of humidity due to temporal variation in water availability throughout the growing season. The most common observed species included \u003cem\u003eAgrostis stolonifera, Alopecurus pratensis\u003c/em\u003e, \u003cem\u003eCentaurea stoebe\u003c/em\u003e, \u003cem\u003eGalium aparine\u003c/em\u003e, \u003cem\u003eGalium mollugo\u003c/em\u003e, \u003cem\u003eRanunculus acris\u003c/em\u003e and \u003cem\u003eUrtica dioica\u003c/em\u003e.\u003c/li\u003e\n \u003cli\u003e\u003cem\u003eMeadows and roadsides\u003c/em\u003e. Plants were harvested from the edges of meadows and roadsides of forest areas. Seeds were collected from meadow habitats located between small forest fragments, between copses, in clear-cuts, on road edges, in fresh meadows and herbaceous meadows, at the edges of forests and open areas such as pastures. In this combination of meadow, forest and ruderal vegetation a rich species diversity occurs. Among the observed species were \u003cem\u003eAchillea millefolium\u003c/em\u003e, \u003cem\u003eArrhenatherum elatius\u003c/em\u003e, \u003cem\u003eCampanula patula\u003c/em\u003e, \u003cem\u003eCentaurea jacea\u003c/em\u003e, \u003cem\u003eHypericum perforatum\u003c/em\u003e,\u003cem\u003e\u0026nbsp;Knautia arvensis\u003c/em\u003e, \u003cem\u003eLeucanthemum vulgare\u003c/em\u003e, \u003cem\u003eLotus corniculatus\u003c/em\u003e, \u003cem\u003ePlantago lanceolata\u003c/em\u003e, \u003cem\u003ePotentilla argentea\u003c/em\u003e and \u003cem\u003eVeronica chamaedrys\u003c/em\u003e.\u003c/li\u003e\n \u003cli\u003e\u003cem\u003eRailway tracks\u003c/em\u003e. Samples were collected along the tracks with typical ruderal vegetation harbouring species such as \u003cem\u003eAgrostis capillaris\u003c/em\u003e, \u003cem\u003eArtemisia vulgaris\u003c/em\u003e, \u003cem\u003eChenopodium album\u003c/em\u003e, \u003cem\u003eMatricaria discoidea\u003c/em\u003e, \u003cem\u003ePapaver rhoeas\u003c/em\u003e, \u003cem\u003eRubus caesius\u003c/em\u003e, \u003cem\u003eSaponaria officinalis\u003c/em\u003e, \u003cem\u003eStellaria media\u003c/em\u003e, \u003cem\u003eTaraxacum officinalle\u003c/em\u003e, \u003cem\u003eTrifolium arvense\u003c/em\u003e, \u003cem\u003eVicia hirsuta\u003c/em\u003e and \u003cem\u003eViola arvensis\u003c/em\u003e.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003e\u003cem\u003eMargins of agricultural fields\u003c/em\u003e. In this habitat type several field species were observed, including \u003cem\u003eArenaria serpyllifolia\u003c/em\u003e, \u003cem\u003eAvena fatua\u003c/em\u003e, \u003cem\u003eCentaurea cyanus\u003c/em\u003e, \u003cem\u003eConvolvulus arvensis\u003c/em\u003e, \u003cem\u003eEuphorbia exigua\u003c/em\u003e, \u003cem\u003eEuphorbia helioscopia\u003c/em\u003e, \u003cem\u003eLithospermum arvense\u003c/em\u003e, \u003cem\u003eMyosotis arvensis\u003c/em\u003e, \u003cem\u003eNeslia paniculata\u003c/em\u003e, \u003cem\u003eStachys annua\u003c/em\u003e, \u003cem\u003eTrifolium repens\u003c/em\u003e, \u003cem\u003eVeronica persica\u003c/em\u003e and \u003cem\u003eVicia angustifolia\u003c/em\u003e.\u003c/li\u003e\n \u003cli\u003e\u003cem\u003eTree orchards\u003c/em\u003e. Plants were sampled at the base of orchard trees and in the area surrounding the orchards. Despite a distance of approximately 15 km, the visited sites harboured similar species, including \u003cem\u003eCapsella bursa-pastoris\u003c/em\u003e, \u003cem\u003eChenopodium album\u003c/em\u003e, \u003cem\u003eEquisetum arvense\u003c/em\u003e, \u003cem\u003eErigeron canadensis\u003c/em\u003e, \u003cem\u003eLamium purpureum\u003c/em\u003e, \u003cem\u003ePlantago major\u003c/em\u003e, \u003cem\u003ePoa annua\u003c/em\u003e, \u003cem\u003ePolygonum aviculare\u003c/em\u003e, \u003cem\u003ePotentilla anserina\u003c/em\u003e, \u003cem\u003eSenecio vulgaris\u003c/em\u003e, \u003cem\u003eTaraxacum officinalis\u0026nbsp;\u003c/em\u003eand \u003cem\u003eVeronica persica\u003c/em\u003e.\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eCluster analysis of the collecting sites based on species composition resulted in 10 different groups (Fig. 4; Suppl. Table 4). G1 consisted only of samples collected along agricultural fields (habitat \u0026nbsp;type 5) and included all \u003cem\u003eV. dentata\u003c/em\u003e accessions. These environments harbour rich segetal and ruderal plant communities occurring in rendzina soils, characterized by species typical for these soils, such as \u003cem\u003eBupleurum rotundifolium\u003c/em\u003e, \u003cem\u003eCaucalis daucoides\u003c/em\u003e, \u003cem\u003eNeslia paniculata\u003c/em\u003e, \u003cem\u003eRanunculus arvensis\u003c/em\u003e, \u003cem\u003eStachys annua and Thymelaea passerina\u003c/em\u003e. G2 comprised meadows and roadsides and orchard habitats (type 3 and 6) and G3 mainly areas along railway tracks and along agricultural fields (type 4 and 5). G1-G3 together formed a major cluster, characterized by a large diversity of associated species observed at the collecting sites. The second major cluster is divided in two subclusters, respectively consisting of G4-G7 and G8-G10. G4 included only riparian and floodplain sites (habitat type 2) and showed a poor species diversity, while G5-G7 each consisted of combinations of habitat types (respectively 1, 2, 3 and 5; 1, 3 and 5; 1 and 3) and were found to be more divers in species composition. Nearly all collecting sites included in G5-G7 shared the species \u003cem\u003ePlantago lanceolata\u003c/em\u003e, \u003cem\u003ePoa annua\u003c/em\u003e and \u003cem\u003ePotentilla argentea\u003c/em\u003e. Also each of G8-G10 was constituted by combinations of habitat types. G8 included types 1, 2, 3 and 4 and G9 types 1, 3, 4 and 5, which represented the highest species diversity of all collecting sites. G10 was formed by types 1, 2, 3 and 5, including a great share of grasses, as well as \u003cem\u003eRumex crispus\u003c/em\u003e. \u003cem\u003eArrhenatherum elatius\u003c/em\u003e occurred in groups G8-G10 and was shared by all sampled sites.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSeed characteristics\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTSW values of the collected seed samples varied among the collecting sites and differed markedly between habitat types (Suppl. Table 4). Lowest values were found for river dike slopes (habitat type 1) and floodplain sites (type 2). Meadows and roadsides (type 3) and railway tracks (type 4) showed intermediate TSW, while the highest values were observed for margins of agricultural fields (type 5) and orchards (type 6). All \u003cem\u003eV. dentata\u003c/em\u003e samples originated from margins of agricultural fields and showed relatively high TSW, likewise the \u003cem\u003eV\u003c/em\u003e. \u003cem\u003elocusta\u003c/em\u003e samples collected from this habitat type (Fig. 5). Analysis of variance (ANOVA) revealed a significant effect of habitat on TSW (F₅,₄₅ = 33.55, p \u0026lt; 0.0001). Tukey HSD post hoc tests showed that habitats 5 and 6 had the highest TSW values and did not differ from each other, whereas habitat 1 had the lowest TSW values. Habitats 2, 3, and 4 showed intermediate values, partially overlapping with the values from the other habitats. TSW was found to be positively correlated (r = 0.47, p \u0026lt; 0.001) with the altitude of the collecting site (Fig. 5). As habitat type and altitude of the collecting site do not represent completely independent variables, a PCA was carried out to identify the site characteristics that contribute most to the observed variation in TSW (Fig. 6). The first principal component, accounting for 73.2% of the variation was composed of \u0026nbsp;TSW value (r = 0.94, p \u0026lt; 0.001) and habitat type (r = 0.92, p \u0026lt; 0.001). The second principal component, explaining 21.6% of the variation, was ascribed to altitude (r = 0.73, p \u0026lt; 0.001). Thus habitat type had a stronger effect on TSW than altitude. \u0026nbsp;\u0026nbsp;\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eCWR taxonomy\u003c/h2\u003e \u003cp\u003eVarious concepts are in use to determine which wild plant species can be considered relatives of a crop species. The gene pool concept is probably the most practical for plant breeders as it is based on the ability to transfer genes from wild species to a crop (Harlan \u0026amp; de Wet 1971). According to this concept species are assigned to the primary gene pool in case of interfertility, to the secondary gene pool in case of limited interfertility and to the tertiary gene pool when special techniques are required such as embryo rescue and bridge crosses. In this sense wild \u003cem\u003eV. locusta\u003c/em\u003e can be considered a primary gene pool species of cultivated corn salad. The use of the gene pool concept for corn salad is complicated by the fact that interfertility data for wild species are usually lacking for understudied crops. Alternatively, existing taxonomic hierarchy may be used as a proxy for CWR relatedness with the cultivated crop (Maxted \u003cem\u003eet al\u003c/em\u003e. 2006). According to this concept wild \u003cem\u003eV. locusta\u003c/em\u003e can be assigned to taxon group 1, while species with missing crossing information but belonging to same genus as the crop are assigned to taxon group 4.\u003c/p\u003e \u003cp\u003eIn the present study we used the botanical name \u003cem\u003eValerianella locusta\u003c/em\u003e as the basis for our inventory of corn salad CWR and summarized all species sharing the same genus name. As the crop species has recently been reassigned to the genus \u003cem\u003eValeriana\u003c/em\u003e (POWO 2025) it can be argued that our CWR survey should have focussed on this genus. \u003cem\u003eValeriana\u003c/em\u003e represents the biggest genus within the \u003cem\u003eValerianaceae\u003c/em\u003e, comprising 446 accepted species names (POWO 2025). The 54 \u003cem\u003eValeriana\u003c/em\u003e species that previously were assigned to the genus \u003cem\u003eValerianella\u003c/em\u003e were addressed as corn salad CWR in our survey (Suppl. Table\u0026nbsp;2). The CWR status is less straightforward for the additional 392 \u003cem\u003eValeriana\u003c/em\u003e species, of which 337 (86%) have their native distribution outside Europe (Suppl. Table\u0026nbsp;5). Their genetic relationship with cultivated corn salad may be low as the crop species originated from Europe (Péron \u0026amp; Rees 1998). Moreover, a molecular study using several representatives of the genera belonging to the \u003cem\u003eValerianaceae\u003c/em\u003e revealed a separate, relatively homogeneous, group of \u003cem\u003eValerianella locusta\u003c/em\u003e and the nine other investigated congeneric species within the phylogenetic tree (Hidalgo \u003cem\u003eet al\u003c/em\u003e. 2010). Therefore, for most \u003cem\u003eValeriana\u003c/em\u003e species the CWR status and usefulness for corn salad breeding remains to be determined.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eCWR accessibility\u003c/h2\u003e \u003cp\u003eEnsuring proper access to the genetic resources maintained in crop collections is one of the main responsibilities of gene banks in order to link conservation with utilization (Engels \u0026amp; Visser 2003). Despite their importance for crop improvement, CWR generally show limited representation in genetic resources collections (Castañeda-Álvarez \u003cem\u003eet al\u003c/em\u003e. 2016; Khoury \u003cem\u003eet al\u003c/em\u003e. 2010). Sufficient budget needs to be available to cover the expenses related to a collecting expedition, which can be considerable in case of faraway distribution areas. In addition, \u003cem\u003eex situ\u003c/em\u003e maintenance of wild species can be a burden to gene bank curators because regeneration may be laborious, often requiring specific expertise for germination, flowering and seed production. Moreover, legislation regarding access and benefit sharing of genetic resources has become more and more stricter over the years, often requiring time-consuming administrative processes with the host country, if successful at all (EU 2025).\u003c/p\u003e \u003cp\u003eIn addition to representation in genetic resources collections, availability of seed samples for utilization forms another issue regarding access to CWR. It has been shown that poor collection accessibility is mainly due to regeneration backlogs causing insufficient quantity and quality of seed stocks for distribution and utilization (Khoury \u003cem\u003eet al\u003c/em\u003e. 2010). Approximately half of the 103 accessions of corn salad CWR documented in Genesys are conserved by the Millennium Seed Bank Kew that only supplies seeds for non-commercial purposes (MSB 2025). With 20 accessions documented in Genesys, the Israeli gene bank is the second largest maintainer of corn salad CWR, but accession availability can be questioned as no seed requesting procedures or conditions could be found on the institutional website (IGB 2025). Thus, the breeding industry has only poor access to corn salad CWR for crop improvement purposes.\u003c/p\u003e \u003cp\u003eThe quality and quantity of plant seeds collected in the wild are usually insufficient for direct long-term \u003cem\u003eex situ\u003c/em\u003e conservation and distribution to users. It is therefore common practice that newly collected seeds first enter a seed multiplication programme. The seeds of the corn salad CWR collected during the expedition in Poland are planned by CGN for regeneration in the Netherlands in 2026 following the protocols available from their website (CGN 2025). Successfully regenerated accessions will then be included in the collections of CGN and INHORT and documented in their institutional databases as well as in the EURISCO catalogue (ECPGR 2025). Seed samples will be made available for distribution to the user community under the Standard Material Transfer Agreement (SMTA) of the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA 2025).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eDiversity survey\u003c/h2\u003e \u003cp\u003eThe general aim of gene banks is to develop collections representing the genetic diversity of a crop gene pool as much as possible with a minimum level of redundancy (Frankel \u0026amp; Brown 1984). Poland is located in the centre of the European distribution area of wild \u003cem\u003eV. locusta\u003c/em\u003e and is therefore expected to harbour a rich diversity for this corn salad CWR. This diversity was sampled as wide as possible during our expedition by collecting seeds from a wide eco-geographic range. \u003cem\u003eV. locusta\u003c/em\u003e is characterised by the following ecological habitat indicators: \u003cem\u003ei.\u003c/em\u003e light index L5, i.e. full light; \u003cem\u003eii.\u003c/em\u003e thermal index T4-5, i.e. moderately warm climatic conditions; \u003cem\u003eiii.\u003c/em\u003e soil moisture index W3-2, i.e. dry or fresh; \u003cem\u003eiv.\u003c/em\u003e soil or water acidity index R4, i.e. neutral soil (6 \u0026lt; = pH \u0026lt; 7); \u003cem\u003ev.\u003c/em\u003e soil granulometric index D3-4, i.e. sand or sandy loam and silty formations and \u003cem\u003evi.\u003c/em\u003e organic matter content index H2, i.e. mineral-humus soil (Zarzycki \u003cem\u003eet al.\u003c/em\u003e 2002). These indicators clearly reflect the plasticity of \u003cem\u003eV. locusta\u003c/em\u003e and point towards a strong adaptative capacity, enabling the species to occur and survive in various habitats and in different associations of plant communities. The large variation in habitat types and species composition observed for the collecting sites in the present study was in line with this presumed plasticity. Accession PolVal24-037 was found to be particularly interesting because it was collected from the crevices of a stone wall along a side walk. The ability of \u003cem\u003eV. locusta\u003c/em\u003e to survive and reproduce under these extremely unfavourable habitat conditions indicates a high tolerance to abiotic stress and the ability to adapt to limited resources, such as minimal soil content and restricted water availability.\u003c/p\u003e \u003cp\u003eHabitats are considered to be strongly linked with species (Bunce \u003cem\u003eet al\u003c/em\u003e. 2013). The \u003cem\u003eValerianella\u003c/em\u003e samples were collected from a wide range of habitat types and plant associations, but a hierarchical cluster analysis did not reveal a clear relationship between these population parameters. Habitat classification was based primarily on their spatial distribution and ecological characteristics, such as environmental conditions, structure, and location. Species occurring in each habitat were considered as supplementary information supporting the classification. Consequently, plant species were not strictly grouped by habitat type, as species characteristic for a given habitat were not always present. Furthermore, species were recorded that were most abundant at a collection site, while less common species were disregarded. Therefore, the data reflect common habitat characteristics rather than a complete floristic inventory. The classification was based on EUNIS Habitat Classification (Chytrý \u003cem\u003eet al.\u003c/em\u003e 2020) and a combination of others modeling strategies (Ferrier \u0026amp; Guisan 2006).\u003c/p\u003e \u003cp\u003eTSW values of the collected \u003cem\u003eValerianella\u003c/em\u003e samples varied markedly among the habitat types of the origin site. Variation in TSW between different habitats may result from a plastic phenotypic response and/or from genetic differences between populations. Phenotypic plasticity in seed mass, often expressed as TSW, is a commonly observed mechanism by which individual genotypes can modify their investment in offspring size and mass in response to environmental conditions (Gnan \u003cem\u003eet al.\u003c/em\u003e 2014; Razzaque \u0026amp; Juenger 2022). Mechanisms that determine the increase or decrease in seed mass in more challenging habitats include, among others, limited plant resources such as water and nutrients, thermal stress, and a shortened growing season. In response to these factors, plants may increase individual seed mass, i.e. the so-called \"quality over quantity\" strategy, which improves seedling survival in harsh conditions, or reduce seed mass and increase seed number, i.e. the \"bet-hedging\" strategy (Marinoni \u003cem\u003eet al.\u003c/em\u003e 2022). From an ecological and biogeographic perspective, observed seed mass gradients, e.g. with altitude, rainfall or soil type, are well documented (Zhao \u003cem\u003eet al.\u003c/em\u003e 2022). Tracking this variation allows us to understand how populations respond to local conditions and which populations may represent a valuable source of tolerance traits for breeding programs (Veselá \u003cem\u003eet al.\u003c/em\u003e 2020). The specific microhabitat in which PolVal24-037 persisted, demonstrated the high degree of plasticity of \u003cem\u003eV. locusta\u003c/em\u003e, including tolerance to drought stress, nutrient deficiencies and temperature fluctuations. Resistances to abiotic stress are valuable traits in response to changing environmental conditions, such as caused by climate change, and are of great importance in breeding improved crop varieties. Proper access to the wide diversity of CWR is therefore indispensable for a sustainable agriculture and to ensure food security (Dostatny \u0026amp; Dajdok 2020; Vincent \u003cem\u003eet al.\u003c/em\u003e 2013).\u003c/p\u003e \u003c/div\u003e "},{"header":"Concluding remarks","content":"\u003cp\u003eCrop improvement increasingly depends on proper access to the wide genetic diversity contained in their CWR. The CWR of corn salad are characterised by poor representation in current genetic resources collections and limited availability to the breeding industry. The collecting expedition carried out in Poland in 2024 is the first comprehensive collecting activity for corn salad CWR in a country. The expedition materials comprise a rich diversity and greatly extend the genetic resources of corn salad available, not only to plant breeders, but to other users of gene bank collections as well. To further strengthen \u003cem\u003eex situ\u003c/em\u003e collections of corn salad it is recommended that \u003cem\u003eV. locusta\u003c/em\u003e is systematically sampled from other parts of its distribution area. Other potentially interesting corn salad CWR can be collected as bycatch during expeditions and explored for their usefulness in crop improvement.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eConflicts of Interest\u003c/h2\u003e \u003cp\u003eThe authors declare no conflicts of interest.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis work was supported by the targeted grants of the Ministry of Agriculture and Rural Development in 2024 in accordance with grant agreement no. DHR.bz.070.1.2024 for the Institute of Horticulture-National Research Institute, signed on 30 April 2024 (author D.F.D.)\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eD.F.D: Collection (inventory), conceptualization, original draft preparation, methodology, data counting and analysis, writing. R.V.T: Collection (inventory), conceptualization, methodology, data gathering, writing. All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors are grateful to Wojciech Szymański, Zygmunt Dajdok and Karol Bubel for their help in the collecting activities.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAll data supporting the findings of this study are available within the paper and its Supplementary Information.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eBeghia R, Giovenzanaa V, Civellia R, Malegorib C, Burattib S, \u003cem\u003eet al\u003c/em\u003e. (2014) Setting-up of a simplified handheld optical device for decay detection in fresh-cut \u003cem\u003eValerianella locusta\u003c/em\u003e L. 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J Exp Bot 73(16):5682-5697. doi:10.1093/jxb/erac231.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table","content":"\u003cp\u003eTable 1 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"genetic-resources-and-crop-evolution","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"gres","sideBox":"Learn more about [Genetic Resources and Crop Evolution](https://www.springer.com/journal/10722)","snPcode":"10722","submissionUrl":"https://submission.nature.com/new-submission/10722/3","title":"Genetic Resources and Crop Evolution","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Biodiversity conservation, corn salad, crop wild relatives, genetic resources, habitat variation, Poland, seed collecting, Valerianella","lastPublishedDoi":"10.21203/rs.3.rs-8397525/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8397525/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eWild plant species represent a rich source of genetic variation and are therefore indispensable as a source of novel traits for crop improvement. Despite their importance crop wild relatives (CWR) are generally underrepresented in genetic resources collections. Here we performed an inventory of the CWR of corn salad (\u003cem\u003eValerianella locusta\u003c/em\u003e), a leafy vegetable that has increased in interest as food crop, and investigated their representation in genetic resources collections. In addition, we reported on the diversity collected for corn salad CWR during an expedition in Poland in 2024. Exploring the plant database Plants of the World Online, our inventory resulted in 79 CWR of which only 22 were represented in the genetic resources data repository Genesys. Focusing on the European distribution area resulted in 32 CWR of which only seven were included in Genesys with a total of 51 accessions. \u003cem\u003eV. locusta\u003c/em\u003e occurs in the wild throughout Europe but only 15 accessions originating from only four European origin countries were encountered in Genesys. The collecting expedition covered most of Poland and resulted in 59 new accessions, including 54 of \u003cem\u003eV. locusta\u003c/em\u003e, four of \u003cem\u003eV. dentata\u003c/em\u003e and one of \u003cem\u003eV. carinata\u003c/em\u003e. The expedition materials originated from a wide variety of habitat types and plant associations, while a large diversity in thousand-seed weight was observed among the accessions. It was concluded that CWR are poorly represented in current genetic resources collections of corn salad. The expedition was the first systematic collecting effort for corn salad CWR in a country and the collected materials greatly extend the genetic resources of corn salad available to the user community of gene bank collections.\u003c/p\u003e","manuscriptTitle":"Exploring and conserving genetic resources of corn salad: distribution and collecting of wild Valerianella spp. species in Poland","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-08 13:53:43","doi":"10.21203/rs.3.rs-8397525/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-02-22T15:21:42+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-16T13:04:22+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-08T10:57:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"33017345054950373221539100185038118405","date":"2026-02-04T09:02:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"50988080418318327495074333786909222405","date":"2026-02-02T09:18:29+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"339801562832788288804024732461170083294","date":"2026-01-18T07:35:59+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-06T14:06:16+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-29T11:49:36+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-29T11:48:12+00:00","index":"","fulltext":""},{"type":"submitted","content":"Genetic Resources and Crop Evolution","date":"2025-12-18T15:53:34+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"genetic-resources-and-crop-evolution","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"gres","sideBox":"Learn more about [Genetic Resources and Crop Evolution](https://www.springer.com/journal/10722)","snPcode":"10722","submissionUrl":"https://submission.nature.com/new-submission/10722/3","title":"Genetic Resources and Crop Evolution","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"43cda739-cc50-46d0-8de1-afefad92c8c7","owner":[],"postedDate":"January 8th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-19T16:23:14+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-08 13:53:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8397525","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8397525","identity":"rs-8397525","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}