重庆市烟草赤星病菌致病力测定

利用离体叶片悬滴接种法,将2005年在重庆市各烟区采集分离的烟草赤星病24个代表菌株进行了致病力测定。结果显示,所有测试菌株均具有致病力,但存在明显的致病力差异,其中强致病力菌株5个,较强菌株8个,中等致病力菌株10个,弱致病力菌株1个,分别占供试菌株的20.8%、33.3%、41.7%和4.2%。这表明试验分离获得的大多数菌株致病力居中或偏强。对来源性不同的菌株的致病力进行分析比较,发现重庆各烟区菌株的致病力有所不同,而且同一烟区的菌株致病力也存在一定的差异。离体叶片试验表明,赤星病菌不同病原菌株对烟草叶片的穿透生长能力与致病力呈明显的正相关。

Studies on the pathogenicity differentiation of Alternaria alternata in Chongqing

The pathogenicity of twenty-four strains of Alternaria alternata,isolated from different regions of Chongqing in 2005,was measured.These strains were used to inoculate the detached leaves with spore suspension liquid.All of the strains showed pathogenicity to some extent.The pathogenicity differentiation among the strains was found through the disease index of tobacco leaves infected by brown spots.Five of the 24 strains were most virulent;8 strains were relatively powerful virulent;10 strains were moderately virulent;only one strain showed weak virulence.The results indicated that the majority of the isolated strains were powerfully virulent.For all strains tested,the pathogenicity difference existed in different tobacco-growing regions and even in the same region.It was also found that the ability for mycelium penetrating into detached leaves and its growth was positively correlated to its pathogenicity.