Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/18/2006
Publication Date: 7/27/2006
Citation: Rehner, S.A., Posada, F.J., Buckley, E.P., Infante, F., Castillo, A., Vega, F.E. 2006. Cryptic lineage diversification, mating potential and recombination in the mitotic insect pathogenic fungus beauveria bassiana. Journal of Invertebrate Pathology.93(2006) P.11-21 Interpretive Summary: Beauveria bassiana is a soil-inhabiting fungus that attacks and kills a wide range of important agricultural insect pests. Before B. bassiana can be approved for mass release as a biological control agent, its impact on natural populations of B. bassiana must be determined. In this study, new molecular approaches for identifying species in B. bassiana are described. Also, molecular markers were developed to determine whether or not reproduction by B. bassiana is sexual or asexual. A significant conclusion of this study is that B. bassiana is sexually reproducing. Another significant outcome of this research is the development of molecular tools that make possible the assessment of the genetic interaction between biocontrol strains and naturally occurring individuals of B. bassiana. These markers are useful to scientists performing basic research on Beauveria bassiana, to industry for verifying the genetic origins of commercial strains of B. bassiana,
Technical Abstract: The cosmopolitan fungal entomopathogen Beauveria bassiana is characterized by copious mitotic reproduction via haploid conidiospores, hence it has been assumed that this species is asexual. The recent discovery in Asia of a Cordyceps sexual phase for B. bassiana challenges the longstanding premise of exclusive clonality. However, reproductive mode in B. bassiana populations outside of Asia, where only asexual reproduction has been observed, has not been investigated. In this study, we use genealogical concordance based on phylogenies of three nuclear genes to delineate terminal clades of isolates as candidates for population genetic analysis. To investigate whether or not B. bassiana is recombining, we scrutinized a pair of sister lineages that includes a clade from northeast Asia, which is known to reproduce sexually and a presumptively asexual clade of isolates from Europe. Statistical tests of allele associations among polymorphic microsatellite loci in these populations indicate that both are recombining. The presence in both populations of mating-type genes, which regulate fertilization and sexual development in ascomycetes, is demonstrated, supporting the conclusion that both populations are intrinsically sexual.