Genetic analyses place most Spanish isolates of Beauveria bassiana in a molecular group with word-wide distribution

Inmaculada Garrido-Jurado,Rosa Hermosa,Cándido Santiago-Álvarez,Enrique A Iturriaga,Almudena Ortiz-Urquiza,Marcela Márquez,Enrique Quesada-Moraga,Enrique Monte

doi:10.1186/1471-2180-11-84

Inmaculada Garrido-Jurado, Rosa Hermosa + Show 6 more

Open Access

https://doi.org/10.1186/1471-2180-11-84

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Abstract

BackgroundThe entomopathogenic anamorphic fungus Beauveria bassiana is currently used as a biocontrol agent (BCA) of insects. Fifty-seven Beauveria bassiana isolates -53 from Spain- were characterized, integrating group I intron insertion patterns at the 3'-end of the nuclear large subunit ribosomal gene (LSU rDNA) and elongation factor 1-alpha (EF1-α) phylogenetic information, in order to assess the genetic structure and diversity of this Spanish collection of B. bassiana.ResultsGroup I intron genotype analysis was based on the four highly conserved insertion sites of the LSU (Ec2653, Ec2449, Ec2066, Ec1921). Of the 16 possible combinations/genotypes, only four were detected, two of which were predominant, containing 44 and 9 members out of 57 isolates, respectively. Interestingly, the members of the latter two genotypes showed unique differences in their growth temperatures. In follow, EF1-α phylogeny served to classify most of the strains in the B. bassiana s.s. (sensu stricto) group and separate them into 5 molecular subgroups, all of which contained a group I intron belonging to the IC1 subtype at the Ec1921 position. A number of parameters such as thermal growth or origin (host, geographic location and climatic conditions) were also examined but in general no association could be found.ConclusionMost Spanish B. bassiana isolates (77.2%) are grouped into a major phylogenetic subgroup with word-wide distribution. However, high phylogenetic diversity was also detected among Spanish isolates from close geographic zones with low climatic variation. In general, no correlation was observed between the molecular distribution and geographic origin or climatic characteristics where the Spanish B. bassiana isolates were sampled.

Highlights

The entomopathogenic anamorphic fungus Beauveria bassiana is currently used as a biocontrol agent (BCA) of insects
Analysis of group I introns in 3’ LSU rDNA The 3’-end of the nuclear LSU rDNA genes of the 57 B. bassiana isolates (Table 1) was amplified with primers I29 and M1 and four different sizes of PCR products were observed on agarose gels, ranging from 0.79 to 1.77 kb
After sequencing analysis (Table 2), we observed that the smallest PCR products were detected in 3 out of the 57 isolates studied-coded Bb19, Bb50 and Bb57- indicating that these isolates had no introns, and the intronless sequence size was 790 bp; identical in composition to a homologous fragment of B. bassiana s.l. [25] described previously

Summary

Introduction

The entomopathogenic anamorphic fungus Beauveria bassiana is currently used as a biocontrol agent (BCA) of insects. Morphological and molecular studies have shown that the broad patterns of diversity in Beauveria have been accurately predicted in previous morphological studies They have shown that these approaches are insufficient to investigate species such as B. bassiana [8]. Molecular data applied to taxonomic investigations have demonstrated that B. bassiana is a species complex with several cryptic species and have corroborated their link to Cordyceps teleomorphs [8,9,10,11,12] In this sense, phylogenetic studies based on nuclear ITS and elongation factor 1-alpha (EF1-a) sequences have demonstrated the monophyly of Beauveria and the existence of at least two lineages within B. bassiana s.l. Studies on the genetic variability of BCAs such as B. bassiana are crucial for the development of molecular tools for their monitoring in the natural environment [6]

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