Abstract: One hundred and twenty-nine Magnaporthe grisea isolates from Guangdong, Guangxi, Anhui and Jiangsu provinces of China in 2000 were tested for resistance frequency to kitazin P and carbendazim respectively at distinctive concentrations. The resistance frequency of M. grisea isolates to kitazin P, which had not been used in practice for about 10 years was as high as 79.1% and one carbendazim-resistant isolate was detected in Gaoyao City, Guangdong Province (with a frequency of 0.78%). Meanwhile, the minimum inhibition concentration (MIC) of hyphal melanization was adopted to detect the sensitivity of Magnaporthe grisea to the inhibitor, tricyclazole. The melanin biosynthesis in M. grisea showed several different sensitive degrees to tricyclazole, but no correlation between these MIC values completely inhibiting melanization in hyphal and the EC₅₀ values of tricyclazole against rice blast tested in vivo was observed. Kitazin P-resistant mutants and carbendazim-resistant mutants were recovered by chemical taming and UV irradiation, but none tricyclazole-resistant mutant was got.

Key words: Magnaporthe grisea, fungicide resistance, kitazin P, carbendazim, tricyclazole, mutant

摘要： 用区分剂量法检测了2000年采自中国广东、广西、安徽和江苏四省129株稻瘟病菌对异稻瘟净和多菌灵的抗药性频率。稻瘟病菌对生产上已停用10年左右的异稻瘟净的抗药性频率仍高达79.1%；在广东省高要市检测到了一例多菌灵抗药性菌株GY5，频率为0.78%。利用抑制菌丝黑色素化的最小抑制浓度（MIC）离体检测了稻瘟病菌对三环唑的敏感性，结果表明稻瘟病菌黑色素的生物合成对三环唑存在着不同的敏感性基因水平，但没有观察到上述MIC值与活体条件下测定的防治稻瘟病的[i]EC[/i][sub]50[/sub]间存在相关性。用药剂驯化和紫外诱变的方法都获得了稻瘟病菌抗异稻瘟净突变体和抗多菌灵突变体，但未能获得抗三环唑突变体。

关键词: 稻瘟病菌, 抗药性, 异稻瘟净, 多菌灵, 三环唑, 突变体