Chen Xue, Huang Cui, He Lingmin, Zhang Shengli, Li Zengzhi
Anhui Provincial Key Laboratory of Microbial Control, Anhui Agricultural University, Hefei 230036, China.
Anhui Provincial Key Laboratory of Microbial Control, Anhui Agricultural University, Hefei 230036, China.
J Invertebr Pathol. 2015 Feb;125:16-22. doi: 10.1016/j.jip.2014.12.005. Epub 2014 Dec 23.
The fungal pathogen Beauveria bassiana causes serious economic losses in sericulture. Its origin is usually attributed to the release of B. bassiana insecticides against pine caterpillars (Dendrolimus punctuatus). In the present study, 488 B. bassiana isolates obtained from silkworm (Bombyx mori) collected from 13 Chinese provinces, and 327 B. bassiana isolates obtained from D. punctatus collected from 9 provinces, were analyzed for population genetic structure using the ISSR technique based on genetic distance. A UPGMA dendrogram clustered them into three independent clades: two B. mori clades and one D. punctatus clade. A 3-D principal component analysis further divided them into two completely independent host groups, revealing high host-specificity. This suggested that white muscardine occurring in B. mori populations throughout southern China was not caused by any B. bassiana strain either naturally prevailing in D. punctatus populations or by any strain artificially released as a fungal insecticide against D. punctatus. We further investigated the genetic differentiation coefficient Gst and gene flow between B. mori-pathogenic and D. punctatus-pathogenic B. bassiana isolates from across China and from five provinces inhabited by both B. mori and D. punctatus. The Gst value across China was computed as 0.410, while the values of the five provinces ranged from 0.508 to 0.689; all above 0.25, which is the threshold for significant genetic differentiation. This suggests that B. bassiana strains isolated from the two different hosts maintained their respective heredity without a convergent homogenization trend, and reduces the possibility that the host range of the caterpillar isolates could expand and enhance their virulence in B. mori. These findings indicate that the use of B. bassiana does not threaten the safety of sericulture.
真菌病原体球孢白僵菌在养蚕业中造成严重经济损失。其来源通常归因于用于防治松毛虫（马尾松毛虫）的球孢白僵菌杀虫剂的释放。在本研究中，使用基于遗传距离的ISSR技术，对从中国13个省份采集的家蚕（桑蚕）中获得的488株球孢白僵菌分离株，以及从9个省份采集的马尾松毛虫中获得的327株球孢白僵菌分离株进行了群体遗传结构分析。一个UPGMA聚类图将它们聚为三个独立的分支：两个家蚕分支和一个马尾松毛虫分支。三维主成分分析进一步将它们分为两个完全独立的宿主组，显示出高度的宿主特异性。这表明在中国南方各地家蚕种群中出现的白僵病不是由马尾松毛虫种群中自然存在的任何球孢白僵菌菌株，也不是由作为防治马尾松毛虫的真菌杀虫剂人工释放的任何菌株引起的。我们进一步研究了来自中国各地以及家蚕和马尾松毛虫都有的五个省份的家蚕致病型和马尾松毛虫致病型球孢白僵菌分离株之间的遗传分化系数Gst和基因流。全国范围内的Gst值计算为0.410，而五个省份的值在0.508至0.689之间；均高于0.25，这是显著遗传分化的阈值。这表明从两种不同宿主分离的球孢白僵菌菌株保持了各自的遗传性，没有趋同的同质化趋势，并降低了毛虫分离株的宿主范围扩大并增强其在家蚕中的毒力的可能性。这些发现表明使用球孢白僵菌不会威胁养蚕业的安全。
