LESION DEVELOPMENT AND SPORULATION OF RICE BLAST

Sporulation intensity of blast lesions over time followed a distributi on curve skewed to the right. Old lesions had very low sporulation int ensities. Lesions grow substantially during their development. With re spect to total sporulation potential, lesion size therefore partly com pensates for low sporulation intensity of old lesions. Sporulation int ensity of individual lesions can be judged by means of visual criteria such as lesion color and zonation. Mean duration of the infectious pe riod i in the field was 11.5, 8, and 7.5 days for lesions on leaf blad es, leaf sheaths, and panicle necks, respectively. Lesion development was significantly affected by ontogenetic host factors and environment . Duration of i, final lesion size, and estimated sporulation capacity could be explained by 47, 23 and 45 % based on negative effects of le af age at infection time, positive effects of soil moisture tension, a nd temperature influences. Wetness conditions correlated positively wi th these lesion parameters.