云南不同蚕区僵蚕致病菌株的分离鉴定及致病力差异研究

Isolation,identification and pathogenicity difference of Bombyx batryticatus pathogenic strains from different silkworm areas in Yunnan province

[目的]了解云南省不同蚕区家蚕僵蚕病原的多样性及不同来源白僵菌菌株对家蚕的致病力差异。[方法]从云南省9个县(市)收集僵蚕样品,分离纯化获得病原菌,通过观察菌株的形态特征、产孢结构,并结合菌株核糖体rDNA-ITS序列的系统发育分析,确认病原种类。同时测定分析不同地理来源以及不同孢子浓度的球孢白僵菌菌株对家蚕致病力的影响。[结果]形态学和ITS序列分析发现,云南蚕区僵病病原菌属于白僵菌属(Beauveria)、虫草菌属(Cordyceps)和绿僵菌属(Metarhizium),其中以球孢白僵菌(Beauveria bassiana)和莱氏绿僵菌(Metarhizium rileyi)为主要病原,分别占57.58%和30.30%。不同地理来源的球孢白僵菌株对家蚕幼虫的致病力存在一定差异,供试菌株侵染后,家蚕的僵蚕率在72.5%~95.0%,半致死时间(LT50)在5.093~7.133 d,其中LL1-1菌株的僵蚕率最高(95.0%),半致死时间最短(5.093 d),致病力最强;CB1-2菌株的僵蚕率较低(75.0%),半致死时间最长(7.133 d),致病力最弱。随着接种浓度的增加,病原的致病力变强,家蚕的僵蚕率也升高。[结论]云南省蚕区家蚕僵病病原种类呈多样性,球孢白僵菌和莱氏绿僵菌为主要病原菌,不同来源的白僵菌株对家蚕的致病力存在差异,本研究结果可为家蚕僵病的防治和僵蚕的生产提供参考依据。

[Objective]The present paper aimed to understand the diversity of Bombyx batryticatus pathogen in different silkworm areas and the difference in pathogenicity of Beauweria bassiana strains from different sources to silkworm in Yunnan province.[Method]Pathogens were isolated and purified from silkworm samples collected from 9 counties(cities)in Yunnan provincial silkworm rearing areas.The pathogenic species were identified by observing the morphological characteristics and sporulation structure of the strains,combined with the phylogenetic analysis based on ribosomal rDNA-ITS sequences.Furthermore,the effects of B.bassiana from different geographical sources and different spore concentrations on pathogenicity were also determined and analyzed.[Result]The pathogens of muscardine disease in Yunnan silkworm areas belonged to the genera Beauveria,Metarhizium and Cordyceps,among which B.bassiana and Metarhizium rileyi were the main patho-gens,accounting for 57.58%and 30.30%respectively.There were certain dfferences in the pathogenicity of B.bassiana strains from dif-ferent geographical sources to silkworm larvae.The batryicated silkworm rate of the tested strains was from 72.5%to 95.0%,and the half-lethal time(LTso)was between 5.093 and 7.133 days.Among them,the LL1-1 strain had the highest batryticated silkworm rate(95.0%),the shortest half-lethal time(5.093 days),and showed the strongest pathogenicity.In contrast,the CB1-2 strain had the lowest ba-tryicated silkworm rate(75.0%),the longest half-lethal time(7.133 days),and showed the weakest pathogenicity.Moreover,with the in-crease in the concentration of inoculation pathogen,its pathogenicity became stronger,and the batryicated silkworm rate also increased.[Conclusion]The pathogenic species of silkworm muscardine disease in Yunnan province are diverse.B.bassiana and Metarhizium rileyi are the main pathogens,and the pathogenicity of B.bassiana strains from different sources to silkworm are different.The results of the study can provide a reference for the control of muscardine disease and the production of batryticated silkworm.