Distribution of Fertile Magnaporthe grisea Fungus Pathogenic to Rice in Yunnan Province, China.

Abstract

Three hundred eight isolates of Magnaporthe grisea were collected from rice plants in 14 counties of Yunnan Province, China in 1988-89. Each isolate was tested for mating type and fertility with Mat1-1 and Mat1-2 female fertile tester strains. Three percent of these isolates consisted of Mat1-1, and 23% of Mat1-2. The remaining 74% isolates did not produce perithecia in crosses with both Mat1-1 and Mat1-2 fertile testers. The percentage of fertile isolates in each county ranged from 90% in Lincang to 0% in Lijiang, Dali, and Honghe. Almost all the isolates were differentiated into races based on the reaction of Japanese differential cultivars. Sixteen races were identified within the fertile isolates. Isolates of both mating types were found in two counties, Qujing and Xishuangbanna, and those in Xishuangbanna were slightly interfertile. In contrast, crosses between the hermaphroditic isolate CHNOS37-1-1 from Xishuangbanna and three male isolates from other counties led to the successful production of large numbers of perithecia containing viable ascospores. The crosses were fertile enough to permit the isolation of germinating ascospores. The southwestern area where fertile blast fungi were isolated with a considerable frequency, coincided with the area with a high diversity of rice cultivars.