Devi K Uma, Reineke A, Reddy N Nageswara Rao, Rao C Uma Maheswara, Padmavathi J
Department of Botany, Andhra University, AP India.
Genome. 2006 May;49(5):495-504. doi: 10.1139/g06-004.
Beauveria bassiana, a mitosporic fungus used for the biological control of many insect species, is recognized as a "species complex" comprising genetically diverse lineages. Being predominantly asexual, mating tests cannot be applied to delimit species in this species complex. Genetic tests offer an indirect means of identifying species among isolates. To this end, molecular genetic analysis of a sample of B. bassiana isolates with 2 subsamples, 1 representing a worldwide collection and another from a localized epizootic population was carried out. DNA markers generated through AFLPs (amplified fragment length polymorphisms) and SSCPs (single-strand conformation poly morphisms) and nucleotide sequence data of different allelic forms of 3 genes (large and small subunits of rRNA and beta-tubulin) were evaluated. The B. bassiana isolates from the worldwide sample showed 11% overall similarity and no closely clustered groups. Phylogenetic trees generated from the AFLP and SSCP data of this sample resolved the different isolates into distinct phylogenetic lineages. In the epizootic B. bassiana population, prevalence of recombination was evident from random association of alleles in multilocus tests and lack of phylogenetic concordance among 3 gene genealogies. Thus, the worldwide sample of B. bassiana exhibits a predominantly clonal structure, hinting at species divergence leading to cryptic speciation with recombination being customary among isolates sharing a close ecological niche.
球孢白僵菌是一种用于生物防治多种昆虫的丝孢真菌，被认为是一个“复合种”，由基因多样的谱系组成。由于其主要进行无性繁殖，交配试验无法用于界定该复合种中的物种。基因检测提供了一种间接识别分离株中物种的方法。为此，对球孢白僵菌分离株样本进行了分子遗传分析，该样本有两个子样本，一个代表全球收集的样本，另一个来自局部流行种群。评估了通过扩增片段长度多态性（AFLP）和单链构象多态性（SSCP）产生的DNA标记以及3个基因（rRNA的大亚基和小亚基以及β-微管蛋白）不同等位基因形式的核苷酸序列数据。来自全球样本的球孢白僵菌分离株总体相似度为11%，没有紧密聚类的群体。从该样本的AFLP和SSCP数据生成的系统发育树将不同的分离株解析为不同的系统发育谱系。在流行的球孢白僵菌种群中，多位点试验中等位基因的随机关联以及3个基因谱系之间缺乏系统发育一致性表明重组现象普遍存在。因此，全球球孢白僵菌样本呈现出主要为克隆的结构，这暗示着物种分化导致了隐存种的形成，而在共享紧密生态位的分离株之间重组是常见的。
