Effects of temperature and pathogen isolate on laboratory screening of soybean for resistance to Sclerotina sclerotiorum

The effects of temperature and pathogen isolate on laboratory screening of soybean (Glycine max. L.) for resistance to Sclerotinia sclerotiorum were investigated. The screening procedure used excised stems from 5-wk-old plants. Temperature and isolate significantly affected the length of stem lesions on 15 and 10 cultivars, respectively. At 15 °C, lesions were significantly shorter, but there was no difference in lesion length between 20 and 25 °C. One of the isolates caused significantly shorter lesions. There were significant differences among cultivars, but there were no temperature × cultivar or isolate × cultivar interactions. Choice of isolate and temperature between 15 and 25 °C, therefore, should not affect the relative differences among cultivars when screened for resistance using the excised stem method. Maple Presto, Maple Arrow and Maple Ridge were the most resistant of 19 cultivars evaluated. Key words: Soybean, resistance, temperature, isolate, Sclerotinia sclerotiorum