利用离体叶片悬滴法 ,将从云南烟区采集、分离的烟草赤星病菌 39株分别接种到感病品种RG1 7上 ,在保湿培养箱中测定其致病力。结果表明 ,病菌不同菌株致病力有明显的差异。其中 ,致病力强的菌株有 6株 ,病指为 6 0～ 95 ,最高的两个菌株为 97Aa 0 .0 3和 98Aa 6 1 2 ,病指分别为 95 .0和 94.4;致病力中等的菌株有 8株 ,病指为 1 5～ 47.5 ;致病力弱的菌株有 1 5株 ,病指在 1 0以下 ;还有 1 0个菌株不致病。病菌来源说明 ,在不同的烟区中都存在着致病力不同的菌株。大理、楚雄两烟区分离的菌株致病力普遍较低 ;昆明菌株致病力很不均衡 ;玉溪、红河、曲靖菌株致病力较均衡 ,致病力不同的菌株均出现。在同一地块的同一烟株上也存在着致病力不同的菌株 Thirty-nine isolates of tobacco brown spot disease, which were collected and isolated from Yunnan tobacco growing areas, were inoculated onto the susceptible cultivar RG1 7 using leaf hanging method. The pathogenicity of the isolates was determined in a humidified incubator. The results show that the pathogenicity of different strains of bacteria have obvious differences. Among them, there are 6 strains with strong pathogenicity, the pathogenic index is 60 ~ 95, the highest two strains are 97Aa0.03 and 98Aa612, the pathogenic index is 95.0 and 94.4 respectively; There were 8 moderate strains with 15 ~ 47.5 pathogenicity; 15 pathogenic strains with less than 10 pathogenicity; and 10 strains were not pathogenic. Pathogen sources indicate that there are pathogenic strains in different tobacco zones. The virulence of strains isolated from Dali and Chuxiong were generally lower; the pathogenicity of Kunming strains was very unbalanced; strains with more pathogenicity and pathogenicity appeared in Yuxi, Honghe and Qujing strains. In the same land of the same tobacco plants also have different virulence strains