Genomics of host and habitat adaption in an entomopathogenic fungus
Final Report Abstract
The cosmopolitan anamorphic fungus Beauveria bassiana (Ascomycota: Hypocreales) is a well recognised entomopathogen known to infect hundreds of insect host species and is an active ingredient of several commercially available biological pest control products. Beauveria bassiana is usually sprayed on the plant’s foliage or directly onto the soil. Besides its pathogenic nature towards insects the fungus can survive saprotrophically in the soil environment for extended periods of time. However, the genetic basis of adaptation to different habitats as well as the impact of artificially applied B. bassiana on the natural soil fungal communities is poorly understood so far. We established a molecular marker method based on the amplification of six B bassiana strain specific microsatellite (SSR) markers and applied this technique to study the persistence of a B. bassiana isolate present in a commercial product (Naturalis) in the soil. This product was applied to different types of potting media with and without plants in the greenhouse as well as onto soil cultivated with ornamental plants. DNA extracted from soil samples was analysed for the presence of the respective B. bassiana isolate. For some SSR markers, specific detection of B. bassiana in soil samples was possible up to 19 weeks after application, with no effects of type of potting media or plant species on B. bassiana persistence being evident. In addition, tag-encoded 454 pyrosequencing of the fungal ITS1-region was conducted to assess the effect of an artificially applied B. bassiana isolate on fungal communities in agricultural soils in India. Cultivated and uncultivated fields being ca. 450 km apart and with different backgrounds regarding the natural occurrence of entomopathogenic fungal epizootics were chosen for this approach. In both field sites fungal communities were analysed before and after the application of B. bassiana for a duration of up to 8 weeks. Amplification of fungal ITS-1 fragments from total DNA extracted from soil samples was possible. Phylogenetical assignment of obtained sequences will provide a first insight into the diversity of fungal species in agricultural soils in India and will help us to understand the effect of an artifically applied entomopathogenic fungus on naturally occuring soil fungal communities. An additional aim of this project was to study the mode of expression patterns of genes in B. bassiana which have a putative role in virulence and pathogenicity. Five genes with a predicted function were chosen based on results of a previous collaborative project and primers for qPCR were designed to verify their expression patterns both in vitro (if the fungus is grown in liquid media containing cuticle extracts from different insects) and in vivo (if the fungus infects living insects). qPCR conditions have been optimized and different cDNA templates will now be analysed in a successive project.
