Meyling Nicolai V, Lübeck Mette, Buckley Ellen P, Eilenberg Jørgen, Rehner Stephen A
Department of Agriculture and Ecology, University of Copenhagen, Frederiksberg C, Denmark.
Mol Ecol. 2009 Mar;18(6):1282-93. doi: 10.1111/j.1365-294X.2009.04095.x. Epub 2009 Feb 17.
Although intensively investigated for biological control of insect pests, little is known about the ecology of the fungal entomopathogenic genus Beauveria in natural or agricultural habitats. In this study, we used molecular phylogenetic and genotypic information to infer species diversity, reproductive potential and genetic structure of Beauveria occurring within a single arable field and bordering hedgerow in Denmark. Isolates were sampled from cultivated field and hedgerow soils, from insects harbouring latent fungal infections, and from the phylloplanes of three plant species common in the hedgerow flora. A nuclear phylogeny of this local Beauveria assemblage resolved seven phylogenetic species, including (i) five phylogenetic species within Beauveria bassiana sensu stricto; (ii) Clade C, a taxonomically uncharacterized species that is morphologically indistinguishable but phylogenetically distant from B. bassiana s.s.; and (iii) Beauveria brongniartii. All seven species were present throughout the hedgerow habitat, including as infections in insects. Significantly, only B. bassiana s.s. phylogenetic species Eu_1 was isolated from tilled soils. Mating type polymerase chain reaction assays demonstrated that all five B. bassiana s.s. phylogenetic species possess bipolar outcrossing mating systems. Of these, only the Eu_1 population contained two mating types; however, a 31:2 skew in MAT1:MAT2 mating types suggests a low frequency of sexual reproduction in this population. The four remaining B. bassiana s.s. phylogenetic species were fixed for single mating types and these populations are evidently clonal. Multilocus microsatellite genotyping revealed polymorphism in all five phylogenetic species of B. bassiana s.s.; however, all show evidence of clonal genetic structure.
尽管对昆虫病原真菌进行了深入研究以用于害虫的生物防治,但对于球孢白僵菌属在自然或农业生境中的生态学却知之甚少。在本研究中,我们利用分子系统发育和基因型信息来推断丹麦一块耕地及其毗邻树篱内球孢白僵菌的物种多样性、繁殖潜力和遗传结构。从耕地和树篱土壤、携带潜伏真菌感染的昆虫以及树篱植物群落中常见的三种植物的叶面上采集分离株。对该地区球孢白僵菌组合的核系统发育分析确定了7个系统发育种,包括:(i)严格意义上的球孢白僵菌内的5个系统发育种;(ii)进化枝C,一个分类学上未明确的物种,其形态上与严格意义上的球孢白僵菌无法区分,但系统发育上与之相距甚远;(iii)布氏白僵菌。所有7个物种都存在于整个树篱生境中,包括感染昆虫。值得注意的是,仅从耕作土壤中分离出了严格意义上的球孢白僵菌系统发育种Eu_1。交配型聚合酶链反应分析表明,所有5个严格意义上的球孢白僵菌系统发育种都具有双极性异交交配系统。其中,只有Eu_1群体包含两种交配型;然而,MAT1:MAT2交配型的31:2偏差表明该群体中进行有性繁殖的频率较低。其余4个严格意义上的球孢白僵菌系统发育种都固定为单一交配型,这些群体显然是克隆的。多位点微卫星基因分型显示,严格意义上的球孢白僵菌的所有5个系统发育种都存在多态性;然而,所有这些种都显示出克隆遗传结构的证据。