海南椰心叶甲病原菌金龟子绿僵菌的分离、鉴定及其生防潜力

摘要

椰心叶甲[Brontispa longissima(Gestro)]是椰子的重要害虫,近年来,该虫在海南岛发生普遍,椰子受害严重.由于椰心叶甲受到自然界中某些致病微生物的侵袭,在受害的椰子树心叶上常可发现椰心叶甲僵虫,并发现大部分僵虫表面长出了霉菌,本研究的目的在于从椰心叶甲僵虫表面的霉菌中分离出绿僵菌,并对分离菌株进行鉴定和致病性测定.从僵虫表面刮下孢子或菌丝体,置于绿僵菌选择性培养基(DOA)上培养,挑出真菌菌落,经纯化后,进行生物学特性、菌落生长速率及产孢量的测定,并从PPDA、OMA、V8A和PDA中筛选菌落生长及产孢最适培养基,同时对所分离的菌株进行对椰心叶甲的致病性测定.结果表明,所有分离菌株均鉴定为金龟子绿僵菌[Metarhizium anisopliae(Metschnikoff)],PPDA是菌落生长及产孢的最适培养基,大多数菌株对椰心叶甲有较强的致病力.选取强毒菌株MA4在田间进行防治效果的初步测定,结果表明,该菌株能显著降低椰心叶甲成虫的虫口密度.这些金龟子绿僵菌菌株是首次从海南的椰心叶甲僵虫中分离到的昆虫病原真菌,该菌对海南的椰心叶甲具有很好的生防潜能.%Coconut hispid beetles, Brontispa longissima (Gestro) (Coleoptera:Chrysomelidae) have been prevalent all over Hainan Island in China, and millions of coconut palms were attacked by this pest. The objective of this work was to isolate and identify strains of entomopathogenic fungi from natural infections of B. longissima collected from coconut palms.Conidia or mycelia collected from the surface of beetle cadavers were cultured and the colonies were screened on dodine oatmeal agar medium (DOA). The colony morphology, mycelia growth rate and conidial production were further studied on various agar media: PPDA, OMA, V8A and PDA. In order to confirm whether these isolates were pathogenic to B.longissima, their virulence to the beetles were also tested in laboratory. The results showed two different kinds of strains MA and MB were all identified as Metarhizium anisopliae(Metschnikoff) base on the macromorphological and micromorphological characteristics, and PPDA was the optimal culture medium for vegetative growth and conidial production. Several high virulent strains were screened in vitro, and application on controlling coconut hispid beetles was carried out preliminarily in vivo. The results showed a significant reduction in adult population was caused by the isolate. It was proved that M.anisopliae isolated from the natural infected cadavers of B. longissima have great potential as a means of biocontrol against this serious pest.