Abstract: Three hundred and forty two monoconidial isolates were obtained from rice blast specimens collected from five typical areas in Jiangsu Province during 2000-2002. The isolates could be classified into seven groups, thirty races when they were assessed with seven Chinese differential rice cultivars. The race ZG₁ was predominant one with a frequency of 65.00% in 2000, 56.90% in 2001 and 60.38% in 2002; the races ZB and ZC groups were important ones in Jiangsu Province. By inoculating 130 ZG₁ race isolates on 13 Japanese cultivars with known resistance genes, 42 pathotypes were found, 30.77% of ZG₁ race isolates which was predominant pathotype were virulent to the Shin 2(Pita-k^s,Pi-^_sh) ,K1(Pi-ta), Pi 4(Pi-ta²,Pi-sh), suggesting that the resistances of Shin 2(Pita-k^s,Pi-sh),K1(Pi-ta), Pi 4(Pi-ta²,Pi-sh) had lost in Jiangsu Province. K3(Pi-k^h) was highly resistant to Magnaporthe grisea in Jiangsu Province with 100% of resistance frequency. When two isolates, 2003 184(ZC₅) and 2003-14-1(ZG₁), with different virulences were mixed to inoculate, K3 (Pi-k^h) which has resistance to the two isolates respectively was infected by the mixed isolates. It indicated the change of virulence resulted from the interaction among different pathotype isolates was one of the reasons that made variety lose its resistance.

Key words: Magnaporthe grisea, pathological race, distribution, virulence

摘要： 用中国7个统一鉴别品种对2000~2002年江苏省5大稻区采集的342个稻瘟病菌单孢分离菌株进行了小种鉴定。结果表明3年累计出现7群30个小种，其中ZG1为优势小种，3年的频率分别为65.00%、56.90%和60.38%，ZB群和ZC群生理小种也是重要的小种类型,有较高的出现频率。用130个ZG1小种的菌株对日本13个已知抗性基因品种进行毒力测定，出现42种类型毒力，其中30.77％的ZG1小种的菌株同时对品种新2号（Pita-k[sup]s[/sup]，Pi-sh）、K1（Pi-ta）、Pi-4号（Pi-ta[sup]2[/sup]，Pi-sh）致病，为优势毒力类型, 表明品种新2号（Pita-ks，Pi-sh）、K1（Pi-ta）、Pi-4号（Pi-ta[sup]2[/sup]，Pi-sh)与江苏省稻瘟病菌有较高的适合度。品种K3（Pi-k[sup]h[/sup]）在江苏省有较好的抗性，其抗性频率为100%。用两种毒力类型的不同菌株2003-184(ZC[sub]5[/sub])和 2003-14-1(ZG[sub]1[/sub]) 混合接种13个日本已知抗性基因品种后，发现对上述两个单个菌株表现抗病的K3（Pi-k[sup]h[/sup]）品种表现为感病，提示不同毒力的菌株之间的相互作用导致菌株毒力的改变可能是品种抗性丧失的原因之一。

关键词: 稻瘟病菌, 生理小种, 分布, 毒力