我国烟草赤星病菌遗传多样性的ISSR分析
Genetic diversity analysis of tobacco brown spot pathogens in China by ISSR

为明确我国烟草赤星病的2种主要致病菌链格孢菌Alternaria alternata和长柄链格孢菌A.longipes的地理差异与遗传结构，采用ISSR标记对分离自9个省市的135株烟草赤星病菌进行遗传多样性分析。结果显示，通过正交优化试验建立的烟草赤星病菌ISSR-PCR最佳反应体系稳定性较好，筛选出17条多态性高且稳定的引物，共扩增出192条谱带，其中有177条具有多态性，多态率为92.19%。UPGMA聚类分析结果显示，链格孢菌和长柄链格孢菌的遗传相似性系数分别在0.67~1.00和0.66~1.00之间，遗传相似性系数为0.83时可使链格孢菌和长柄链格孢菌分别划分为5个和6个亚群，其中前者不同地理种群间表现出地理相关性，后者不同菌株随机分组。烟草赤星病菌种群的基因多态性和遗传多样性丰富，链格孢菌和长柄链格孢菌的群体间遗传分化系数分别为0.36和0.37，均存在遗传分化；群居每代迁移数分别为0.89和0.85，不同地理种群间存在基因交流；2种烟草赤星病菌的遗传分化结构表现出相似性。表明我国烟草赤星病菌中的链格孢菌和长柄链格孢菌均存在丰富的遗传多样性，且二者进化方向相似，ISSR标记能较好地揭示烟草赤星病菌种群间的亲缘关系和遗传差异性，可用于其遗传多样性分析。
In order to understand the geographical differences and genetic structure of Alternaria alternata and A. longipes, the two main pathogens of tobacco brown spot in China, genetic diversity analysis of 135 strains of tobacco brown spot pathogens isolated from nine provinces or cities were conducted by using ISSR. The results showed that the stability of ISSR-PCR system established by orthogonal optimization test was high; 17 ISSR primers were screened out with high polymorphism and stable amplification; a total of 192 bands were detected, and 177 of them were polymorphic, with the polymorphic rate up to 92.19%. UPGMA cluster analysis showed that the genetic similarity coefficients of A. alternata were between 0.67 and 1.00, while those of A. longipes were between 0.66 and 1.00. When the genetic similarity coefficient was selected as 0.83, A. alternata and A. longipes strains tested in this study were divided into five and six subgroups, respectively. Among them, the different geographic populations of A. alternata showed geographical correlation, but A. longipes populations were grouped randomly. PopGene analysis results revealed that the genetic diversity and genetic differentiation of A. alternata and A. longipes groups in China were abundant, and the coefficients of population genetic differentiation were 0.36 and 0.37, respectively. The numbers of migrants per generation were 0.89 and 0.85, respectively, indicating frequent gene flow between A. alternata and A. longipes in different geographic regions. The population genetic structure of the two types of pathogens was similar. In conclusion, there was abundant genetic diversity in A. alternata and A. longipes in China, and their evolutionary directions were similar. ISSR markers could be used to reveal the genetic relationship and genetic diversity of the pathogens of tobacco brown spot.