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Effects of Humidity, Temperature, Fertility, and Cultivar on the Reduction of Soybean Seed Quality by Phomopsis sp.. Douglas A. Spilker, Graduate research student associate, Department of Plant Pathology, The Ohio State University, Columbus 43210; A. F. Schmitthenner(2), and C. W. Ellett(3). (2)Professor, Department of Plant Pathology, The Ohio State University, Columbus 43210; (3)Professor, the Ohio Agricultural Research and Development Center, Wooster 44691. Phytopathology 71:1027-1029. Accepted for publication 23 January 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1027.

Effects of different combinations of high (33 C day, 24 C night) and low (26 C day, 16 C night) temperature, and high (90%) and low (43%) relative humidity imposed during plant maturation stages R6R8 on the development of pod and stem blight symptoms, the occurrence of visibly moldy seed, Phomopsis seed infection, and seed germination were investigated for plants of two soybean cultivars maintained in growth chambers at high and low fertility. The temperature-humidity interaction was significant for all parameters studied. High humidity-high temperature resulted in seed with the most Phomopsis infection (49%) and the poorest germination (32%); high humidity-low temperature resulted in fewer Phomopsis-infected seed (33%) and better germination (62%). Both low humidity-low temperature and low humidity-high temperature resulted in the fewest Phomopsis-infected seed (4 and 4%) and seed with the best germination (95 and 96%), respectively. Percentage of moldy seed was also highest (28%) at high humidity-high temperature, lower (9%) at high humidity-low temperature and less than 1% at both low humidity and low temperature and low humidity-high temperature. There were no cultivar or fertility effects.

Additional keywords: potassium.