田间水稻单个病斑中稻瘟病菌的遗传多样性

根据93个单病斑中分离的227个单孢菌株样品的分析，研究了来自同一定殖系统(同一病斑)中稻瘟病菌不同单孢菌株(同源菌株)的遗传变异。在致病性分析的样品中，仅有5个病斑分离的10个单孢菌株在所有鉴别品种上表现同源菌株有完全相同的致病反应，并且有完全相同的DNA指纹图谱带型；另有13个病斑上分离的32个单孢菌株的同源菌株不仅属于不同的生理小种，而且在1～3个单基因品种上也有不同的致病反应。用rep—PCR指纹图谱和致病型分析67个病斑的157个单孢样品中的同源菌株具有完全相同的DNA指纹图谱；13个病斑中分离的27个单孢样品中同源菌株具有显著差异的指纹图谱；8个病斑分离的27个单孢菌株样品中同一来源样品中部分样品有相同的指纹图谱带型，部分样品却有不同的指纹图谱。同源菌株之间有完全相同致病性其指纹图谱亦相同或有很小的差异；通常，致病性差异很大的同源菌株其指纹图谱差异也很大。作者认为来自同一定殖系统中的不同单孢菌株存在的遗传变异与病菌的异核现象或自然状态下不同遗传背景菌株同时侵染造成同一病斑有关。

Genetic variation of Magnaporthe grisea isolates from single rice blast lesion

Genetic variation of 227 monocodial isolates of Magnaporthe grisea from 93 rice blast lesions is analyzed based on pathogenicity and DNA fingerprints with Pot2-rep-PCR. The homogenous isolates from same lesion in 10 isolates from 5 lesions in the tested samples showed same pathogenic reaction on all differentials and same DNA fingerprints; homogenous isolates in 32 isolates from 13 lesions were identified as different races and displayed different pathogenic reactions on the monogenic differentials. The homogenous isolates in 157 isolates from 57 lesions had same DNA fingerprints, while those in 27 isolates from 13 lesions had different DNA fingerprints. Some of homogenous isolates in 27 isolates from 8 lesions had different DNA fingerprints , while others had same ones. Different pathogenicity on race and monogenic differential varieties and different DNA fingerprint haplotypes, i. e. different genetic background in different monoconidial isolates from single lesions revealed heterokaryosis in M. grisea or mixture infection with 2 or more different isolates in same lesion.