中文摘要：

了解稻瘟病菌无毒基因的出现频率及分布，有助于制定有效的合理利用持有不同抗性基因的水稻品种及在多样性种植系统中抗性基因的组合的策略。本文对在云南省11个地（州）采集的稻瘟病菌中无毒基因的出现频率及地理分布进行分析，并利用持有20个抗性基因的水稻单基因系对供试的467个稻瘟病菌株的致病型进行鉴定。结果表明，稻瘟病茵无毒基因在云南省10个地（州）的出现频率差异不显著，而无毒基因在西双纳版纳的出现频率与其它10个地（州）的出现频率之间差异显著；无毒基因Aw—Pi9、Avr-Piz和Avr—Pizt在11个地（州）的稻瘟病菌中出现频率最高，它们的平均检出率在80％以上。本研究结果表明，水稻遗传多样性的组成和分布对于水稻稻瘟病菌遗传多样性的形成和保持比气候和其它环境条件更重要。通过无毒基因的平均出现频率，可将无毒基因划分为4个类群，不同类群的无毒基因出现频率差异显著，而同一类群中的无毒基因出现频率的差异不显著。本研究结果将为水稻抗性基因的评价及稻瘟病有效防控提供有用的信息。

英文摘要：

Knowledge of the geographic distribution and frequency of avirulence genes will contribute to the development of strategies to effectively use rice varieties that carry various resistances genes, including combinations of varieties in mixture cropping systems. Here, we analyzed the geographic distribution and frequencies of avirulence genes in rice blast fungus using samples collected from 11 prefectures across Yunnan province, China. A total of 467 single spore isolates were assayed for pathotypes based on their reaction to 20 rice blast resistance monogenic lines. The results revealed that frequencies of avirulence genes among 10 prefectures showed insignificant difference, but frequencies of avirulenee genes in Xishuangbanna showed significant differences compared to the remaining 10 prefectures. The avirulence genes Avr-Pi9, Avr-Piz and Avr-Pizt were observed at the highest frequency in blast isolates from the 11 prefectures; their average frequency was greater than 80%. Our results imply that the composition and distribution of rice genetic diversity are more important than climate and other environment conditions for formation and maintenance of rice blast fungus genetic diversity. Using average frequencies, the avirulence genes can be categorized into 4 groups. There were significant differences of frequencies of avirulence genes among different groups, while insignificant differences observed within any group. These results will provide useful information for evaluation of resistance genes and effective management of rice blast disease.