Effects of Humidity, Temperature, Fertility, and Cultivar on the Reduction of Soybean Seed Quality byPhomopsissp.

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Abstract
Effects of different combinations of high (33.degree. C day, 24.degree. C night) and low (26.degree. C day, 16.degree. C night) temperature and high (90%) and low (43%) relative humidity imposed during plant maturation stages R6-R8 on the development of pod and stem blight symptoms, the occurrence of visibly moldly seed, Phomopsis seed infection and seed germination were investigated for plants of 2 soybean cultivars [''Wells'' and ''Wayne''] 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 < 1% at both low humidity and low temperature and low humidity-high temperature. There were no cultivar or fertility effects.