(24(3-4):23-31)A SURVEY ON THE PREVALENCE OF PANICLE BLAST OF THE LONG GRAIN INDICA TYPE RICE, WITH SPECIAL EMPHASIS ON THE PHYSIOLOGICAL RACES OF BLAST FUNGUS

民國六十三年第二期作於臺南、嘉義、雲林及南投等四縣栽培之長粒型秈稻（嘉農秈8號及11號）異常發生穗稻熱病，嘉農秈8號之栽培面積1,702.0公頃中，受穗稻熱病為害者高達74.83%，而嘉農秈11號之栽培面積4,270.3公頃中，發生面積為28.95%，由此可知其嚴重性。此兩種稻品種發生穗稻熱病之特性，在被害穗之葉節部位受病原菌之侵害（所稱葉節稻熱病）頗普遍。 自被害稻穗分離所得菌株，經對16判別稻種測定結果，可類別為五羣(Groups)，包括21種不同生理小種(Races)，其中新出現之生理小種有五種之多。在21種生理小種中，屬於I羣者13種，T羣2種，K羣4種，N及A羣者各1種。侵害嘉農秈8號及嘉農秈11號之主要稻熱病菌生理型，前者為Race 55及51，後者為Race 51及31等。由此可知可侵害印度型稻之生理型頗多，今後對稻熱病之發生消長，吾人需特別提高警覺。 The present study was conducted to survey the prevalence of panicle blast in the long grain indica type rice varieties, Chianung-shien 8 and Chianung-shien 11. 74.83% of 1,702 hectares of Chianung-shien 8 and 28.95% of 4,270 hectares of Chianung-shien 11 were heavily damaged by the disease in the 2nd crop of 1974. In addition to the panicle part, the collar of the leaves were also severely infected by the disease. The panicle samples were collected from different diseased areas and the pathogen isolated. The isolates of the pathogen were tested to identify the races based on the disease reaction types on the 16 differential rice varieties. Twenty one races, including 5 new races and 16 previously identified races, were obtained. The further investigation comfirmed that 13 races belong to group I, 2 races belong to T group, 4 races belong to K group, and one race each belong to groups N and A respectively. It was also found that the races 51 and 55 invade exclusively to Chianung-shien 8 and race 31 and 51 to Chianung-shien 11. Results indicated that there are more races infecting indica type rice varieties