Aphanomyces euteiches causes disease in Lathyrus sativus with a globally diverse, polygenic resistance landscape.

Aphanomyces euteiches inoculation of a global Lathyrus sativus collection allowed the identification of sources of resistance and associated candidate genes. Aphanomyces euteiches is a major concern in legume crops with limited efficient methods for its management. Although Aphanomyces root rot has been widely studied in pea and lentil, the effect of this pathogen on grass pea (Lathyrus sativus) has been poorly explored. This study aimed to characterise the response of a globally diverse grass pea collection to A. euteiches and to identify genomic regions associated with any potential resistance. A diverse panel of 169 grass pea accessions was inoculated with the A. euteiches RB84 isolate. Twenty days after inoculation, foliar and root symptoms were evaluated. A wide range of responses was observed within the panel, from susceptibility to partial or even complete resistance. Along with these phenotypic data, an improved acquired 12,974 single-nucleotide polymorphism (SNP) data set was used to perform a genome-wide association study. The association study identified 20 resistance-associated SNPs, across five of the seven grass pea chromosomes, suggesting a polygenic nature. In silico analysis identified seven putative candidate genes associated with resistance involved in vesicle trafficking, signal transduction, nucleotide metabolism, fatty-acid metabolism, cell wall synthesis and ethylene signalling. This study confirms the compatible grass pea × A. euteiches interaction, identifying for the first time, sources of resistance and proposing resistance-associated loci with co-located candidate genes for future precision breeding purposes.