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.
Fusarium root rot, caused by Fusarium solani f. sp. pisi, is one of the most important fungal diseases of pea and is found in most pea-growing areas around the world. Currently, no commercial cultivars are resistant to this pathogen. Availability of new sources of partial resistance could provide another tool for managing Fusarium root rot. In all, 387 accessions from the Pisum core collection were evaluated for resistance to Fusarium root rot in two independent experiments. Nonparametric analysis of variance conducted on ranks of disease severity for each accession indicated that the two experiments corresponded well. Forty-four plant introduction lines with a disease severity rating of 2.5 or less on a 0-to-5 scale (where 5 = completely rotted) were selected as being partially resistant to root rot. Immunity to Fusarium root rot was not found. Comparison of disease resistance data for Aphanomyces root rot and Fusarium root rot showed a weak, but significant and positive correlation. A complete listing of the data for the partial resistance of all accessions tested can be found at the National Plant Germplasm System website, United States Department of Agriculture-Agricultural Research Service.
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