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Title: Identification of tolerance to Fusarium root rot in wild pea germplasm with high levels of partial resistance

Author
item Porter, Lyndon
item Coffman, Virginia

Submitted to: Pisum Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2011
Publication Date: 4/1/2011
Citation: Porter, L., Coffman, V.A. 2011. Identification of tolerance to Fusarium root rot in wild pea germplasm with high levels of partial resistance. Pisum Genetics. 42:1-6.

Interpretive Summary: Fusarium root rot, caused by Fusarium solani f. sp. pisi is a serious root rot disease affecting peas in all pea growing areas of the USA. The disease may damage peas produced in both dryland and irrigated fields, and has been reported to reduce yield between 30 to 57% in eastern Washington and Canada. Early symptoms of the disease are reddish brown to black lesions on the roots that often expand and coalesce as the growing season progresses resulting in severe root rot. Chlorosis and eventual necrosis of lower plant leaves is commonly observed in infected plants and can progresses to upper leaves. Mature plants may be severely stunted or die due to infection. Currently there are no commercial pea cultivars that have been bred for resistance to F. solani. Identifying and incorporating resistant breeding material into future pea cultivars would have a tremendous impact on pea productivity. The present study identified the most resistant pea lines from the Pisum Core Collection with high levels of resistance to Fusarium root rot based on seed germination rates, root disease severity, plant height, fresh and dry foliage weights, and dry root weight of infected verse non-infected pea plants. Four pea lines were determined as having excellent resistance to Fusarium root rot based on root disease severity values. These lines could be used in genetic mapping populations to identify the genes associated with this resistance. Eight lines demonstrated high levels of resistance to Fusarium root rot since root disease severity values of infected plants were low, and the disease did not significantly impact germination rates, plant height, foliage fresh weight, foliage dry weight, or root dry weight when compared to non-infected plants. The lines identified in this study can be used by pea breeders to develop future Fusarium-root-rot-resistant pea cultivars.

Technical Abstract: Fusarium root rot, caused by Fusarium solani f. sp. pisi, is a serious root rot pathogen affecting peas in all pea growing areas of the USA and is damaging in both dryland and irrigated pea fields. Partial resistance to Fusarium root rot in 44 accessions from the Pisum Core Collection located in Pullman, WA was characterized under greenhouse conditions. Germination rates, root rot severity, plant height, foliage fresh weight, foliage dry weight, and dry root weight of inoculated and non-inoculated plants of each accession were assessed. Accessions PI125839, PI198735, PI222071 and PI271119 were identify as excellent selections to generate mapping populations to identify resistant genes associated with partial resistance to Fusarium root rot based on low root disease severity values within each of their respective screening groups in replicated trials. Twelve accessions demonstrated high levels of partial resistance to infection since plant heights were not significantly (P > 0.05) reduced compared to the non-inoculated controls of the same accession in replicated trials. In addition, eight accessions (PI25839, PI125840, PI175226, PI220174, PI2223526, PI2223527, PI226561 and PI227258) demonstrated partial resistance to Fusarium root rot since plant heights, foliage fresh weights, foliage dry weights, and dry root rates of these accessions were not significantly (P < 0.05) different from non-inoculated plants for all screening trials. Five of these eight accessions originated from Afghanistan, and the other three were from India, Iran, and Ethiopia. Germination rates of inoculated and non-inoculated seed of all 44 PI accessions screened were not significantly (P > 0.05) different in two or more trials, indicating a high level of resistance in these accessions to seed rot and pre-emergence damping off.