The study, led by Sara Rodriguez-Mena of the Institute for Sustainable Agriculture in Córdoba, Spain, together with Mario González, Diego Rubiales and collaborators in Portugal and Iran, set out with a simple but urgent question. Grass pea cultivation declined for decades in many regions where Aphanomyces is endemic, which may explain why the pathogen was never reported as a problem in this crop. But renewed interest in grass pea as a model crop for sustainable agriculture, driven by its resilience and its ability to fix atmospheric nitrogen, means that expanded cultivation could bring the crop back into contact with infested soils. As legume acreage grows across Europe and beyond, so too does the risk that Aphanomyces spreads with it. Understanding whether grass pea can withstand this pathogen before farmers commit to the crop is therefore a matter of practical urgency.

To answer it, the researchers assembled a globally diverse panel of 169 grass pea accessions, drawn from the Mediterranean basin, South Asia, Eastern Europe, Sub-Saharan Africa, North Asia and the Americas. The collection spanned differences in seed colour and seed size that would later prove biologically meaningful. Each accession was inoculated under controlled conditions with the RB84 isolate of A. euteiches, a pea-derived strain known for its ability to cross host boundaries and infect multiple legume species. Ten-day-old seedlings received a zoospore suspension adjusted to 1,000 zoospores per millilitre, applied directly at the base of each stem. Twenty days later, the team scored both foliar symptoms on a scale of 0 to 5 and root rot symptoms on a scale of 0 to 9, with the highly susceptible pea cultivar Messire serving as a positive control to confirm that the inoculation had worked.

The results revealed an extraordinary spectrum of responses. Average foliar symptom scores ranged from 0.08 to 4.50, and root rot scores from 1.64 to 8.73, meaning the collection captured everything from near-complete susceptibility to something approaching immunity. Twelve accessions qualified as resistant, with low scores on both scales, and two of them, PI283570_A and PI283580, displayed complete resistance to the tested isolate, a level of protection that has never been documented in pea, where breeders have managed only to identify partial resistance. Ten further accessions showed partial resistance, including STUDENICA, a commercial variety with strong agronomic credentials that could be recommended for cultivation in infested soils right away. Notably, several of the resistant accessions, including PI283580, BGE17185 and PTLS1006, had previously shown low symptom levels against another soil-borne pathogen, Fusarium oxysporum f. sp. pisi, making them doubly valuable given how frequently Aphanomyces and Fusarium co-infect legume fields.

Genotype was the dominant driver of symptom variation, with high broad-sense heritability for both foliar and root scores, exactly the property breeders need for genetic improvement. But seed characteristics left a visible fingerprint too. Accessions with large, light-coloured seeds, which are typical of Mediterranean origins, showed significantly lower disease symptoms than small, dark-seeded accessions of South Asian provenance. This echoes earlier findings in the same collection for Fusarium resistance, hinting that shared defence mechanisms may underpin grass pea tolerance to both soil-borne pathogens. The correlation between foliar and root symptoms was moderate but significant, confirming that what happens underground reliably manifests above ground, as it does in pea.

The real breakthrough came from combining these phenotypes with an upgraded genomic data set. Building on a previously published grass pea reference genome, the team re-called variants from genotyping-by-sequencing data and mapped DArTseq markers onto the seven chromosomes of the L. sativus assembly. The original data set of 26,876 SNPs, of which only 5,651 passed earlier quality filters, was transformed into a far denser resource: 44,383 SNPs detected in total, with 12,974 high-quality markers passing rigorous filtering for minor allele frequency and missing data. This nearly tripled the usable marker count and provided comprehensive genome-wide coverage, giving the association study the resolution it needed.

Using four different genome-wide association models, the team identified 20 SNPs significantly associated with resistance, distributed across five of the seven grass pea chromosomes, with chromosomes 2 and 3 entirely free of associations. Thirteen markers tracked foliar symptoms, eight tracked root rot, and one, SNP007517 on chromosome 6, was associated with both. Two markers, SNP032149 and SNP007517, were independently detected by two different statistical models, reinforcing confidence in their relevance. The proportion of phenotypic variance explained by individual markers ranged from a modest 0.13 percent to 11.62 percent, a pattern that screams polygenic inheritance: no single locus dominates, and resistance emerges from the combined action of many genes scattered across the genome. Clusters of closely linked markers on chromosomes 5 and 6 point to candidate quantitative trait loci that future studies can target with finer mapping.

In silico annotation of the genomic regions surrounding the significant SNPs identified seven putative candidate genes with plausible roles in defence. A wax ester synthase gene on chromosome 1 and a fatty-acid metabolism gene on chromosome 5 connect to evidence that fatty-acid accumulation mediates reactive oxygen species production during Aphanomyces infection in pea. A component of the exocyst complex on chromosome 4, involved in vesicle trafficking, has been implicated in plant immunity, though its specific role against this oomycete remains poorly understood. Chromosome 6 contributed two protein kinase genes and an ethylene receptor gene, and here the parallels with other legumes are striking: serine/threonine protein kinases and ethylene signalling have both been repeatedly linked to Aphanomyces defence in pea and barrel medic, with the ethylene pathway promoting lignin deposition that forms a protective ring around the root’s central cylinder, physically blocking pathogen entry. A callose synthase gene on chromosome 7 rounds out the list, suggesting reinforcement of cell walls at infection sites to limit hyphal spread.

What makes these findings particularly interesting from an evolutionary and agronomic standpoint is that the genomic distribution of resistance markers in grass pea does not overlap with the conserved syntenic QTL regions identified in pea, lentil, faba bean and barrel medic. Grass pea appears to have evolved its own, independently assembled resistance toolkit. This lack of a conserved pattern could complicate cross-species marker transfer, but it also opens exciting possibilities: if breeders can overcome crossability barriers between grass pea and its close relatives, these novel resistance loci could diversify the genetic defences available across legume agriculture, reducing the selective pressure that intensively cultivated, genetically similar crops place on pathogen populations. Because Aphanomyces populations are genetically diverse and reproduce both sexually and asexually, quantitative, polygenic resistance stacked across multiple loci is widely regarded as the most durable long-term strategy, far more robust than reliance on any single resistance gene.

The authors are careful to note the caveats. The RB84 isolate is a pea pathogen, so the response characterised here is a non-host-specific infection; grass pea-specific isolates, if they exist, could be more aggressive and might overcome even the complete resistance observed in PI283570_A and PI283580. Field validation is essential, as is testing against a broader panel of isolates to determine whether the identified regions confer broad-spectrum or pathotype-specific resistance, and whether the two fully resistant accessions owe their protection to monogenic or polygenic mechanisms. Functional validation of the seven candidate genes in planta will clarify their actual roles and guide precision breeding. Still, the significance of this work is hard to overstate. For the first time, breeders have identified sources of resistance to Aphanomyces root rot in grass pea, together with associated loci and candidate genes, transforming an uncharted vulnerability into a well-mapped opportunity. As climate change pushes agriculture toward resilient crops, grass pea may be entering hostile territory, but it is arriving armed with a genetic arsenal that science is only beginning to decode.

Subject of Research: Genetic resistance of grass pea (Lathyrus sativus) to the oomycete root rot pathogen Aphanomyces euteiches

Article Title: Aphanomyces euteiches causes disease in Lathyrus sativus with a globally diverse, polygenic resistance landscape

Article References: Aphanomyces euteiches causes disease in Lathyrus sativus with a globally diverse, polygenic resistance landscape. (n.d.). https://doi.org/10.1007/s00122-026-05372-w

Image Credits: AI Generated

DOI: 10.1007/s00122-026-05372-w

Keywords: grass pea, Lathyrus sativus, Aphanomyces euteiches, root rot, genome-wide association study, polygenic resistance, candidate genes, legume breeding, plant pathology, SNP markers, quantitative resistance, sustainable agriculture

A new study from researchers at Bidhan Chandra Krishi Viswavidyalaya in West Bengal, working with colleagues at ICAR-National Bureau of Plant Genetic Resources in New Delhi and the ICARDA Food Legume Research Platform in Amlaha, offers fresh ammunition for the campaign to rehabilitate this ancient crop. Published in the Indian Journal of Genetics and Plant Breeding, the research systematically evaluated twenty-one grasspea landraces collected from West Bengal, together with two check varieties, across two growing seasons. The team combined classical field measurements of morphological and yield traits with biochemical assays of seed quality and a molecular survey using simple sequence repeat, or SSR, markers. The goal was ambitious but practical: to find out how much hidden diversity these farmer-developed landraces actually contain, how that diversity is organised genetically, and whether any of the lines could serve as donors of both low neurotoxin content and high yield for future cultivar development.

The answer to the first question is emphatically yes. Across the two seasons, the landraces displayed substantial and economically meaningful variability in nearly every trait the researchers measured. Grain yield per plant ranged from 6.98 grams to 14.38 grams, a spread that represents a genuine breeding opportunity rather than background noise. Seed ODAP content varied more than fivefold, from a remarkably low 0.09 percent to 0.46 percent, while soluble protein content ranged from 17.37 percent to 31.07 percent. That protein ceiling is particularly striking, because it demonstrates that some of these unimproved farmer selections already match or exceed the nutritional quality of many conventional pulse crops. In a world where plant-based protein demand is rising and marginal lands are expanding under climate stress, landraces that combine resilience with such protein density are resources worth taking very seriously.

Beneath the raw numbers, the genetic architecture of the traits matters enormously for breeders, and here the study delivered some of its most useful insights. Using generation mean analysis-style reasoning grounded in the partitioning of variance, the team found that additive gene effects predominated for pods per plant, seeds per plant, biological yield, harvest index, grain yield, ODAP content and soluble protein. In practical terms, additive gene action means that the performance of a trait scales roughly predictably with the alleles an individual plant carries, which makes those traits directly amenable to straightforward selection. Breeders can cross a high-performing donor with an elite variety and expect to make steady progress simply by picking the best progeny in each generation, without needing to exploit complex dominance interactions or heterosis. For a crop that has received comparatively little formal breeding attention, the confirmation that its most important traits respond to simple selection is genuinely encouraging news.

Correlation analysis added a second layer of practical guidance. Grain yield showed a strong positive association with pods per plant, with a correlation coefficient of 0.77, identifying pod number as the single most effective primary selection criterion for yield improvement in this material. This kind of indirect selection is a cornerstone of efficient breeding: rather than waiting for full yield data that may be confounded by environmental variation, breeders can reliably screen large populations early for pod production and capture most of the yield signal. The study also found that ODAP content was significantly associated with several key phenological and yield-related traits, suggesting that the neurotoxin is not an isolated biochemical curiosity but is woven into the broader developmental and adaptive physiology of the plant. That linkage has implications for breeding strategy, because it means selection on ODAP alone could inadvertently shift flowering time or yield architecture if the associations are not monitored and managed through careful, multi-trait selection.

To understand how the landraces relate to one another genetically, the researchers turned to molecular markers. SSR markers, which detect variation in short tandemly repeated DNA sequences, remain a workhorse tool for diversity analysis in orphan crops where full genome sequences and high-density SNP arrays are not yet routine. The SSR analysis revealed a moderate level of polymorphism, with a mean polymorphism information content, or PIC, of 0.30. Two markers stood out as especially informative: S_97, with a PIC value of 0.61, and S_33, with a PIC of 0.40. In marker-assisted breeding, high-PIC markers are valuable because they distinguish genotypes efficiently, and S_97 in particular could serve as a useful anchor locus for future fingerprinting, purity testing and association mapping work in grasspea. At the same time, the overall moderate polymorphism pointed to a relatively narrow genetic base among the evaluated landraces, a finding that carries a caution: the diversity captured in this collection, while real, may not be inexhaustible, and broader germplasm exploration could be warranted.

One of the study’s most methodologically satisfying results was the concordance between phenotypic and genotypic clustering. The researchers used multivariate analyses to group the landraces based on morphological and biochemical traits, and separately based on SSR marker data, then applied the Mantel test to compare the resulting distance matrices. The test revealed a moderate but statistically significant correlation between the morphological and molecular distances, validating the trait-based grouping of the material. This matters because it tells breeders that what they see in the field is not an illusion of environment or measurement error; the observable differences among these landraces reflect genuine underlying genetic differentiation. It also means that either type of data, measured alone, provides a reasonably trustworthy guide to the structure of the collection, which is reassuring for breeding programmes that lack the resources to run both kinds of analysis routinely.

The headline deliverables of the work are two stand-out accessions. IC 0634674 was identified as a low-ODAP donor, with seed neurotoxin content of just 0.09 percent, a level that approaches the thresholds considered safe for unrestricted human consumption and that could dramatically reduce the risk of neurolathyrism in communities that depend on grasspea as a staple. Meanwhile, IC 0634670 exhibited superior yield potential at 14.38 grams per plant, the highest in the entire panel. Together, these two lines offer complementary donor profiles: one addresses the safety bottleneck that has stigmatised the crop, and the other addresses the productivity bottleneck that has limited its competitiveness with major pulses. Crossing programmes that pyramid low ODAP with high yield, guided by the additive gene action and pod-number selection criterion documented in this study, now have a clear starting point.

The broader significance of the research extends beyond a single crop. As climate volatility intensifies, agricultural scientists are increasingly looking to underutilised, climate-resilient legumes to diversify food systems, and grasspea is frequently cited as a prime candidate for drought-prone and flood-prone regions of South Asia and sub-Saharan Africa. Studies like this one show that the raw material for that transformation already exists, sitting in farmer fields and gene banks, waiting to be characterised and deployed. By demonstrating that West Bengal’s grasspea landraces harbour usable variation for toxin content, protein quality and yield, and by supplying the genetic and statistical framework to exploit that variation, the researchers have converted a stigmatised orphan crop into a credible breeding target. The next step, transferring the low-ODAP and high-yield donor alleles into locally adapted cultivars through targeted crossing and selection, will determine whether grasspea finally takes its place as a safe, nutritious staple for the marginal lands of the future.

Subject of Research: Genetic diversity and low-ODAP, high-yield donor identification in Bengal grasspea landraces

Article Title: Integrative Morpho-Biochemical and SSR-Based Diversity Analysis of Bengal Grasspea (Lathyrus sativus L.) Landraces Reveals Low ODAP and High-Yielding Donors

Article References: Das, N., Chanda, R., Roy, S., Das, A., Bhattacharya, S., Datta, J., Mandal, G. S., Tripathi, K., Barpete, S., & Kumar, S. (2026). Integrative Morpho-Biochemical and SSR-Based Diversity Analysis of Bengal Grasspea (Lathyrus sativus L.) Landraces Reveals Low ODAP and High-Yielding Donors. Indian Journal of Genetics and Plant Breeding. https://doi.org/10.1007/s44489-026-00049-6

Image Credits: AI Generated

DOI: 10.1007/s44489-026-00049-6

Keywords: grasspea, Lathyrus sativus, landraces, ODAP, genetic diversity, SSR markers, grain yield, protein content, plant breeding, climate-resilient legume, West Bengal, neurolathyrism