感染松墨天牛的金龟子绿僵菌菌株的初步筛选

Preliminary screening of virulent strains of Metarhizium anisopliae against Monochamus alternatus

松墨天牛是松材线虫病的主要媒介昆虫,本文对分离自松墨天牛的6株金龟子绿僵菌,以及从光肩星天牛、大蜡螟、伊藤厚丝角叶蜂和土蝽上分离的各1个菌株,共10个菌株的产孢情况、孢子萌发率进行研究;在此基础上选出金龟子绿僵菌1291、1349和2049三个菌株及球孢白僵菌F-263菌株,采用成虫跗节接种法和幼虫浸渍法进行室内松墨天牛及大蜡螟的毒力测定比较。结果表明,供试绿僵菌菌株对松墨天牛幼虫在接种15天后的感染僵虫率为76.9%～93.1%(1×107孢子/mL);成虫在接种20天后的僵虫率亦达57.9%～75.0%(6.5×105～3.4×106孢子/成虫);2049菌株表现尤其突出;对应的球孢白僵菌F-263对幼虫和成虫的僵虫率分别是96.3%(1×107孢子/mL)和55%(9.7×105孢子/成虫)。但这3个金龟子绿僵菌菌株对大蜡螟的毒力较低,存在较明显的寄主专化性。这3个菌株今后在防治松墨天牛方面具有较大开发应用价值。

Monochamus alternatus is the major vector of pinewood nematode disease, Bursaphelenchus xylopilus. Ten strains of Metarhizium anisopliae, of which six isolated from M. alternatus, and four from Anoplophora glabripennis, Pachynematus itoi, Galleria mellonella and a burrower bug （Cydnidae） at different locations, were tested for the sporogenous ability and spore germination rate. Three strains of M. anisopliae （1291, 1349, and 2049） were selected, and their virulences to M. alternatus and G. rrtellonella larvae were assayed using the adult-conidial attaching method （attaching all tarsi of adult with dry conidial） and larva dip method with Beauveria bassiana strain F-263 as the control. The results indicated that the three strains of M. anisopliae, especially the strain 2049, were highly virulent to M. alternattLs, with the cadaver rates as high as 76.9% -93.1% （1 × 10^7 conidia/mL） and 57.9% -75.0% （6.5 × 10^5 -3.4× 10^6 conidia/individual） for larvae 15 d after inoculation and adults 20 d after inoculation respectively; as contrast, the cadaver rates by the B. bassiana strain F-263 was 96.3 % （1× 107 conidia/mL） and 55.0% （9.7 × 10^5 conidia/individual） for adults and larvae, respectively. However, the virulence of the three strains of M. anisopliae to G. rrtellonella larvae was rather low, and this suggested that they were strong host specific. The three strains may serve as a potential source of biocontrol agents for M. alternatus.