Identification of Characteristics Associated with Resistance to Root Rot Caused by Aphanomyces euteiches in Pea. John M. Kraft, Supervisory Research Plant Pathologist; Department of Agriculture, 24106 N. Bunn Road, Prosser, WA 99350-9687. William L. Boge, Biological Science Laboratory Technician, Vegetable and Forage Crops Production, Agricultural Research Service, U.S. Department of Agriculture, 24106 N. Bunn Road, Prosser, WA 99350-9687. Plant Dis. 80:1383-1386. Accepted for publication 30 August 1996. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1996. DOI: 10.1094/PD-80-1383.

Previous attempts to quantify resistance in pea to Aphanomyces euteiches have involved oospore counts in infected root tips and disease severity ratings to separate resistant from susceptible lines. In a controlled environment with known zoospore inoculum levels, differences in oospore production in infected roots, rate of lesion development in taproots, and zoospore germination in seedling exudates were evident in resistant and susceptible pea lines. Indirect enzyme-linked immunosorbent assay (ELISA) measurements of infected root tissue within a visible lesion revealed a positive, linear regression of lesion length on ELISA readings at 405 nm (R2 = 0.91). Zoospore germination was reduced in seedling exudates from resistant but not from susceptible pea lines. Resistance in pea roots to A. euteiches is associated with reduced oospore production, pathogen multiplication, zoospore germination, and slower lesion development.

Keyword(s): Pisum sativum, root disease, root vigor