来源于同一穗不同稻曲球的稻曲病菌的致病性及遗传多样性

 本研究从源于6穗稻曲病穗的48个稻曲球中分离获得稻曲病菌（Ustilaginoidea virens）48株，从3个稻曲球的不同部位分离获得稻曲病菌23株。用注射接种法将菌株分别接种到水稻品种两优培九（感病品种）、淮稻5号（中抗品种）和武育粳3号（抗病品种）上，结果显示分离的菌株致病力分化较大，而菌株在水稻品种上的致病力强弱与已知水稻品种对稻曲病菌的感、抗性趋势基本一致。相同孢子量接种水稻，不同分离菌株之间仍有致病力分化，生长速率测定也发现菌株之间可能存在差异。利用REP PCR (repetitive extragenic palindromic sequence PCR)技术进行菌株遗传多样性分析表明，同穗不同稻曲球分离的菌株中，1号穗分离的4个菌株聚在同一簇群，其余5穗的菌株分别聚在3～5个簇群；同一稻曲球不同部位分离的菌株中，一个稻曲球分离的8个病菌聚在同一簇群，而其余2个稻曲球分离的病菌则分别聚在2～3个簇群。由此推测同一稻穗上不同稻曲球可能是由来源不同的稻曲病菌侵染所形成；而一个稻曲球可以由同一稻曲病菌引起，也存在多个侵染源共同侵染的可能。

Genetic diversity and pathogenicity of Ustilaginoidea virens isolated from different rice false smut balls of a diseased spike

Rice false smut, caused by Ustilaginoidea virens , is one of the main diseases of rice. We obtained 48 U. virens strains from different rice false smut balls of 6 diseased spikes and 23 U. virens strains from different parts of 3 smut balls, examined the pathogenicity of the strains on three rice cultivars Liangyoupeijiu(susceptible cultivar), Huaidao No.5 (medium resistant cultivar) and Wuyujing No.3(resistant cultivar), growth rate and analyzed their genetic variability using REP PCR. The strains isolated from different false smut balls of a diseased spike had an evident pathogenicity differences on the three cultivars, and were grouped into 3～5 clusters with REP PCR, except the four strains isolated from the No.1 disease spike. In clustering analysis, the isolates of one smut ball clustered together in the same group, and the strains isolated from the other two smut balls in 3 clusters. When inoculated rice with the same amount of conidium, an evident pathogenicity difference of different strains were still found, and the growth rates also showed the difference of the strains. Thus, different strains can infect the same grain or different grains, and a grain also can be infected by the same strain or different strains. However, there was little relationship between groups of strains, based on REP PCR and pathogenicity.