VIEW ARTICLE

Resistance

Determining Resistance Reactions of Field Pea Cultivars at the Seedling Stage to Mycosphaerella pinodes. R. C. Zimmer, Research scientist, Agriculture Canada, P.O. Box 3001, Morden, Manitoba, Canada R0G 1J0; Donald Sabourin, biometrician, Agriculture Canada, Research Station, 195 Dafoe Road, Winnipeg, Manitoba, Canada R3T 2M9. Phytopathology 76:878-881. Accepted for publication 30 January 1986. Copyright 1986 Department of Agriculture, Government of Canada. DOI: 10.1094/Phyto-76-878.

Four field pea (Pisum sativum var. arvense) cultivars were inoculated once, in the seedling stage, with several concentrations of pycnidiospores of Mycosphaerella pinodes. Parameters u and r of the logistic regression of log inoculum concentration on proportion leaf area infected were estimated for each cultivar and used to compare resistance across cultivars. Early in the incubation period, 4 days after inoculation, significant differences in the proportion of leaf tissue infected appeared among the four cultivars. With further incubation, 4-14 days after inoculation, the rates of disease progress among the cultivars varied but were not significantly different. Throughout the incubation period progress in development of the disease was greatest in cultivars Century and Trapper, followed, in order of increasing resistance, by Triumph and Tara. Resistance to development of this disease in field peas was influenced by the cultivar, seedling leaf age, and inoculum concentration. Under conditions marginally favorable for the pathogen, cultivars containing greater levels of rate-reducing resistance will become less severely diseased.