In experiments conducted in a growth chamber, the pathogenicity of a monosporic isolate of Corynespora cassiicola was tested. The isolate was obtained from the leaves of soybean was performed. The isolate of C. cassiicola used was obtained from leaves of soybean from Primavera do Leste, Mato Grosso State, Brazil. The morphology of the conidia under the optical microscope was similar to that of the genus Corynespora. In the assessment of 200 conidia, the following measures were obtained: 8-12 x 20 -280 m, mean of 10 x 150 µm. T he cultivar CD 219 RR was inoculated to prove pathogenicity. Based on the comparison of the symptoms with the descriptions in literature and on the pathogen reisolations followed by its morphological characterization, the pathogenicity of the C. cassiicola isolate used in this work is confirmed. To identify the lower (Lti), and upper (Lts) thermal threshold, as well as the optimal temperature, for the germination of spores, an experiment was performed in Petri dishes containing Czapek agar medium. The tested variables were: (a) exposure times of 6, 12 and 24 hours and (b) low temperatures of 5, 6, 7, 8, 9 and 10ºC, intermediate temperatures of 10, 15, 20, 25, 30 and 35ºC, and high temperatures of 36, 37, 38, 39, 40 and 41ºC. Data were subjected to analysis of variance and regression. The conidia germinated within a wide temperature range presenting Lti of 7ºC, optimal temperature of 23ºC and Lts of 39ºC.
Target leaf spot; soybean; base temperature; Glycine max
