Resistance of peas to Sclerotinia sclerotiorum in the Pisum core collection

Abstract

In this study, 497 pea accessions from the Pisum core collection located at the USDA‐ARS, Western Regional Plant Introduction Station (WRPIS), Pullman, WA and seven woody‐stem pea lines from a private collection in the UK, were screened for resistance to Sclerotinia sclerotiorum, the cause of white mould. All of the Pisum genotypes screened were susceptible to infection, and 237 of the 504 genotypes were highly susceptible since these did not survive 2 weeks post‐inoculation. However, 22 pea accessions and one woody‐stem line were identified with quantitative partial resistance to white mould. Pea accessions 103709, 166084, 169603, 240515 and 270536 from the core collection demonstrated the greatest quantitative partial resistance to S. sclerotiorum based on nodal resistance and plant survival in replicated greenhouse and laboratory tests. Only five of the 504 genotypes screened had a mean lesion length of between 0 and 1 cm when assessed 3 days post‐inoculation. Pea stem diameter was significantly (P ≤ 0·03) negatively correlated with stem lesion length in replicated greenhouse and laboratory experiments, and was determined to be the best predictor of quantitative partial resistance to S. sclerotiorum based on lesion length.