Cell electrofusion to improve efficacy and thermotolerance of the entomopathogenic fungus, Beauveria bassiana.

AIMS: The aim of this study was to optimize the potential of Beauveria bassiana through cell electrofusion technique with emphasis on improving its thermotolerance and virulence against western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae) (WFT).

METHODS AND RESULTS: Nine B. bassiana isolates were tested against western flower thrips, F. occidentalis (Thysanoptera: Thripidae) (WFT) to estimate their pathogenicity and speed of infection under laboratory conditions. The isolates were also exposed to 25, 36, 38 and 40°C, for 24, 48, 72 and 120 h. Two isolates with the highest virulence against WFT and highest thermotolerance were selected and paired using a cell electrofusion technique to obtain a single strain that was both highly virulent and thermotolerant. To determine the hybrid conidia among the fusion cells, each selected isolate was loaded with a different nuclei-staining fluorescent dye before the fusion process. Hybridized fungal strains were acquired by a series of sequential dilutions and were tested for thermotolerance and virulence against WFT. Those that demonstrated both characteristics (high thermotolerance and virulence) similar to or greater than the parental isolates were considered hybrids.

CONCLUSIONS: The results demonstrated that genetic transformation using cell electrofusion can be used to obtain hybrid isolates of fungal pathogens that contain the desired genes from selected isolates. Further DNA-based analysis is required to determine the genetic variation between hybrids and the parental isolates.

SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to demonstrate genetic transformation in B. bassiana by use of cell electrofusion and it could be developed to create superior hybrid isolates with various desired properties for integrated pest management and industrial uses in the future.