曲牙土天牛高毒力绿僵菌菌株筛选

Screening for virulence strains of Metarhizium against Dorysthenes hydropicus pascoes

目的:明确昆虫病原真菌绿僵菌对化橘红害虫曲牙土天牛幼虫的毒力,筛选高致病力菌株,为曲牙土天牛的生物防治提供依据。方法:先利用从化橘红基地土壤中分离及其他实验室提供的36株绿僵菌,制成孢子浓度为1×108个/g的孢子土,对曲牙土天牛1龄幼虫进行初步的毒力测定;在此基础上选取7株分离自化橘红基地土壤的绿僵菌作进一步筛选;并通过液固双相发酵法对筛选出的高毒力菌株的产孢能力进行初步评价。结果:用于作初步毒力测定的36株绿僵菌中,有28株能够侵染曲牙土天牛幼虫,其中6株僵虫率达100%,8株达80%,8株达60%,2株达40%,4株达20%;用于作进一步毒力筛选的7株菌中,有6株表现出较高的毒力,最高僵虫率均大于74%;对这6株菌的产孢量进行测定,产孢量均大于10亿个/g,其中1,4株菌产孢量显著高于其他菌株,分别为2.35±0.25(1×109个孢子/g),2.21±0.27(1×109个孢子/g)。结论:1号和4号菌株对曲牙土天牛1龄幼虫表现出了较高的毒力,并有最强的产孢能力,因此最具开发潜力。

Objective： The aim of the present study was to screen the Metarhizium strains with high virulence against the larvae of Dorysthenes hydropicus, a serious pest of Citrus grandis. Method ： Thirty six strains of Metarhiziums were isolated from the soil of C. grandis GAP base and collected from other institutions, and the pathogenicity of these strains against 1 st instar larvae of D. hydropi- cus was detected at concentration of 1 x 10^8 conidia/g. The high violence strains against D. hydropicus were cultivated in sabouraud dextrose yeast medium at first, then transfer to rice grain. And the sporulations of these violent strains against D. hydropicus were de- tected. Result： Twenty-eight strains showed virulence against D. hydropicus by preliminary study, and 7 strains of them were collected for further study, 6 of the 7 showed high virulence, the highest cadaver rate was higher than 74%. The conidia production of strain 1 and strain 4 were 2. 35 ±0. 25 （ 1 × 109 conidia/g）, 2. 21 ±0. 27（ 1 × 109 conidia/g）, respectively, showed significantly higher than other strains. Conclusion： strain 1 and strain 4 of the 36 Metarhiziums strains showed high virulence against D. hydropicus, and the highest sporulation ability, so they have a best application prospect.