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Factors Affecting Pea Seed and Seedling Rot in Soil. G. E. Short, Former Graduate Research Assistant, Michigan State University, East Lansing 48824, Present address of senior author: Department of Plant Pathology, University of Missouri, Columbia 65201; M. L. Lacy, Associate Professor of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Phytopathology 66:188-192. Accepted for publication 20 August 1975. DOI: 10.1094/Phyto-66-188.

Effects of temperature, soil moisture, cultivar, seed color, and seed treatments on incidence of pea seed and seedling rot in soil naturally infested with Pythium ultimum and artificially infested with Fusarium solani f. sp. pisi, were investigated in controlled environmental chambers and in field plots. Disease incidence was greater with the wrinkled-seeded cultivar Miragreen than with the smooth-seeded cultivar Alaska, and was greater with green than with yellow Miragreen seeds. Seed and seedling rot were greater with high, than with low, soil moisture. Soaking Miragreen seeds in water at 22 C for 48 hours prior to planting reduced incidence of seed and seedling rot below controls, presumably due to removal of the bulk of seed exudates stimulatory to pathogens. However, soaking for 48 hours at 10 or 15 C did not decrease, but usually increased, seed and seedling rot over controls, possibly because of increased exudation due to low-temperature injury. Incidence of rot was greater when growth chamber temperatures were alternated on a diurnal cycle to simulate field conditions than when they were held constant, suggesting that alternating temperatures favored both Fusarium spp. and Pythium spp., which have differing optima for disease development.

Additional keywords: Pythium ultimum, Fusarium solani f. sp. pisi, environmental effects.