Isolation,identification and pathogenicity difference of Bombyx batryticatus pathogenic strains from different silkworm areas in Yunnan province
[Objective]The present paper aimed to understand the diversity of Bombyx batryticatus pathogen in different silkworm areas and the difference in pathogenicity of Beauveria 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 differences 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(LT50)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.
SilkwormMuscardine diseaseIsolation and identificationrDNA-ITS sequence analysisPathogenicity
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