29株虫生真菌的鉴定及对烟粉虱的毒力

【目的】对29株虫生真菌菌株进行分类学鉴定并筛选出对烟粉虱Bemisia tabaci具有高毒力的菌株。【方法】采用形态学及ITS区、TEF区、Bloc区基因序列相似性分析鉴定菌株,并采用浸渍法测定真菌对烟粉虱的毒力。【结果】29株虫生真菌有26株符合白僵菌Beauveria的特征,菌株SB003、SP665和SP670被鉴定属于棒束孢属Isaria;利用TEF区序列、Bloc区序列、TEF-Bloc联合序列构建的系统发育树,结果显示29株菌株共包括24株球孢白僵菌B. bassiana、2株假性球孢白僵菌B. pseudobassiana和3株环链棒束孢I. cateinannulata。烟粉虱2龄若虫的死亡率随孢子浓度的增加而增加,不同菌株致病力不同;用1×108 mL-1的孢子悬浮液处理烟粉虱2龄若虫7 d,致死率最高的菌株为SP433,其次为SB009,分别为87.37%和82.93%。【结论】本研究可为虫生真菌的分类提供理论基础,筛选出的高致病力菌株SP433和SB009可为烟粉虱的生物防治提供参考。

Identification of 29 strains of entomogenous fungi and their toxicity to Bemisia tabaci

Objective To identify 29 strains of entomogenous fungi and select high virulent strains against Bemisia tabaci.Method Identification of fungi were based on morphological analysis and genetic homology analysis of sequences in ITS, TEF and Bloc regions. The fungal toxicity to B. tabaci was evaluated by the immersion method.Result Twenty-six of 29 entomogenous fungal strains had the characteristics of Beauveria and the other three strains of SB003, SP665 and SP670 were identified as Isaria. Phylogenetic tree was constructed using TEF region sequence, Bloc region sequence and TEF-Bloc combined sequence, which showed that 29 strains included 24 strains of Beauveria bassiana, 2 strains of B. pseudobassiana, and 3 strains of Isaria cateinannulata. The mortality of the 2nd instar nymph of B. tabaci increased with the increase of spore concentration, and the pathogenicity of different strain was different. The 2nd instar nymphs of B. tabaci were treated with 1×10⁸ mL^-1 spore suspension for 7 days, and the SP433 strain had the highest lethality rate of 87.37%, followed by SB009 with a lethality rate of 82.93%.Conclusion This study can provide a theoretical basis for the classification of entomophytic fungi. The highly pathogenic strains of SP433 and SB009 were screened out, which can provide a reference for the biological control of B. tabaci.