ABSTRACT

The ability of disease-causing bacteria to synergise infection by the entomopathogen Metarhizium of larvae of Costelytra giveni, a New Zealand native scarab, has been previously demonstrated, but the role of soil bacteria in infections is unknown. Bacteria isolated from both dead C. giveni larvae and soil were assessed for their effect on the virulence of Metarhizium novozealandicum C14 towards C. giveni larvae. Seven bacterial isolates showed synergism with M. novozealandicum C14 against second instar larvae, but no synergism was found against third instar larvae. No apparent disease was noted with C. giveni larvae independently challenged with the bacteria isolates. An isolate of Yersinia enterocolitica (isolate 6-1) in combination with M. novozealandicum C14 caused higher larval mortality than the other bacterial isolate-entomopathogen combinations against second instar larvae. Using plate assays, Y. enterocolitica 6-1 was found to produce more chitinase, but not protease, compared with the other bacterial strains suggesting a role of chitinase in synergism. This study suggests that the combination of Y. enterocolitica (isolate 6-1) and M. novozealandicum C14 could provide effective biocontrol of second instar grass grub larvae.

摘要

先前已经证明，致病细菌能够协同新西兰本地金龟子Costelytra giveni幼虫的昆虫病原体绿僵菌感染，但土壤细菌在感染中的作用尚不清楚。评估了从死亡的给定念珠菌幼虫和土壤中分离出的细菌对新生绿僵菌C14 对给定念珠菌幼虫的毒力的影响。七株细菌分离物与M. novozealandicum C14 对二龄幼虫有协同作用，但对三龄幼虫没有发现协同作用。给定念珠菌未发现明显疾病幼虫独立地受到细菌分离物的攻击。的分离小肠结肠炎耶尔森菌与组合（分离物6-1）M. novozealandicum C14不是对第二龄幼虫的其他细菌分离-昆虫病原体组合引起更高幼虫死亡率。使用平板检测，发现小肠结肠炎耶尔森氏菌6-1 与其他细菌菌株相比产生更多的几丁质酶，但不产生蛋白酶，这表明几丁质酶在协同作用中的作用。该研究表明，小肠结肠炎耶尔森氏菌（分离株 6-1）和M. novozealandicum C14 的组合可以为二龄草蛴螬幼虫提供有效的生物防治。