野外におけるイネいもち病の第一次伝染源に関する研究(1) : ビニール袋に被覆され積雪下で越冬した籾殻におけるイネいもち病菌の生存と第一次伝染源としての役割

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Summary : This study was carried out to investigate the survival of a rice blast fungus on blast-infected rice husks packed in vinyl bags left over the winter around paddy fields and their role as the primary inoculum for initial occurrence of rice blast disease. These rice husks were collected from the bags at numerous locations in south area of Shonai district of Yamagata prefecture on early spring in 2003 and 2004. The fungus had survived the winter on the rice husks in bags at 9 of 13 locations sampled in 2003, and in 10 of 11 locations in 2004. The pot 2 genotypes of the isolates from rice husks were highly diverse even within the same bag. Our results show that rice blast fungus can survive the winter on infected rice husks in the vinyl bags even in areas with at heavy snowfall such as the Japan Sea side of Yamagata Prefecture. The following year, leaf blast occurred in the paddy fields nearest to where the rice husks bags had been left. The Pot 2 genotypes of the rice blast fungus isolated from leaf lesions on rice plants in the paddy fields were identified as being the same as on the rice husk in the bags. We concluded that the overwintered blast-infected rice husks packed in vinyl bags are a key primary inoculum of rice blast disease in the paddy fields.　　Key Words : primary inoculum, rice blast disease, blast infected rice husk packed in vinyl bag　　キーワード：イネいもち病，第一次伝染源，放置籾殻
2008-02-15