Genetic characterization of Beauveria bassiana associated with fire ants, Solenopsis spp. and other insects

Beauveria bassiana isolate 447, obtained from Solenopsis invicta in Brazil, has been developed as a microbial control agent against fire ants in the United States. To genetically characterize isolate 447 and other B. bassiana isolates, including commercial product isolates, various molecular markers were evaluated. The limited DNA sequence heterogeneity of the ribosomal internal transcribed spacers (ITS) and 5.8s rRNA gene region was considered insufficient to efficiently discriminate among isolates by using restriction analysis. Two homologous repetitive DNA sequences (probe 133 and probe 205) and two heterologous probes (a telomeric probe and a mitochondrial probe from Fusarium oxysporum) were able to distinguish isolate 447 from the other commercial product isolates, GHA and Naturalis.; None of 17 isolates from 12 non-fire ant species that were tested with probe 133 and the telomeric probe were similar to isolates from Solenopsis spp. Some B. bassiana genotypes from Solenopsis spp. appear to belong to a Solenopsis genus-preferential clone lineage. Genotype similarity in the lineage suggests a co-evolutionary history between this B. bassiana lineage and Solenopsis spp. Genetic diversity analysis with probe 133, the telomeric probe and single locus probes indicates that asexual reproduction is a predominant reproduction mode among B. bassiana isolates associated with Solenopsis spp. Parsimony analysis suggests that B. bassiana may not be a species with exclusively clonal reproduction.; Probe 133 and the telomeric probe can be used to evaluate the ecological adaptability of isolate 447 as a biological control agent against fire ants. When B. bassiana isolates collected from four Solenopsis species in ten locations were examined, multiple genotypes were commonly found among isolates collected from the same species at the same location. One genotype was predominant regardless of the Solenopsis species or geographic location. This indicates that this predominant genotype, which also includes isolate 447, can survive in a wide range of ecological conditions. After isolate 447 was released at treatment sites in Florida and California, isolates with the same genotype of isolate 447 were recovered one year later, indicating the successful colonization of an exotic isolate released in the United States.