ARS | Publication request: Preliminary study of genetic variation in Hawaiian isolates of Beauveria bassiana [Hypocreales, Cordycipitaceae]

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 9, 2010
Publication Date: February 5, 2011
Citation: Hollingsworth, R.G., Lysy, A., Matsumoto Brower, T.K. 2011. Preliminary study of genetic variation in Hawaiian isolates of Beauveria bassiana [Hypocreales, Cordycipitaceae]. Journal of Invertebrate Pathology. 106 (2011) 422-425.

Interpretive Summary: Beauveria bassiana (Balsamo) Vuillemin is an insect-killing fungus species found worldwide. Quarantine regulations in Hawaii (USA) do not allow the import of pesticide products containing the spores of this fungus because native insect species might be harmed if the strain of fungus in the commercial product becomes established in the environment. We used molecular methods (PCR analysis) to categorize fourteen isolates of B. bassiana collected from insects in east Hawaii island. We used these same molecular methods to categorize the ‘GHA’ strain found in the commercial product BotaniGard®. Twelve of the 14 Hawaiian isolates were found to represent unique strains, and all were different from the GHA strain. We also compared virulence and saprophytic growth ability of the GHA strain with a subset of five of the Hawaiian isolates. Growth rates of the Hawaiian isolates on potato dextrose agar equaled or exceeded the growth rates of the GHA strain on the same medium. In bioassays with Drosophila hawaiiensis Grimshaw (Diptera), Cylas formicarius elegantulus (Summers) (Coleoptera), and Frankliniella occidentalis (Pergande) (Thysanoptera), the killing power of the GHA strain was similar to killing power in one or more of the Hawaiian strains for each insect species tested. Our data do not support the theory that the GHA strain of B. bassiana represents a greater risk to native insects than the strains already present in Hawaii.

Technical Abstract: Beauveria bassiana (Balsamo) Vuillemin is a generalist entomopathogenic fungus found worldwide. State quarantine regulations in Hawaii (USA) prohibit the use of imported biopesticides containing this fungus because of concerns that native insect populations might be adversely affected by the establishment of exotic fungal strains. We used PCR micro-satellite primers to characterize fourteen isolates of B. bassiana collected from insects in east Hawaii island and compared these with the ‘GHA’ strain found in the commercial product BotaniGard®. Twelve of the 14 Hawaiian isolates were unique, and all were different from the GHA strain. We also compared virulence and saprophytic growth ability of the GHA strain with a subset of five of the Hawaiian isolates. Growth rates of the Hawaiian isolates on potato dextrose agar equaled or exceeded the growth rates of the GHA strain on the same medium. In bioassays with Drosophila hawaiiensis Grimshaw (Diptera), Cylas formicarius elegantulus (Summers) (Coleoptera), and Frankliniella occidentalis (Pergande) (Thysanoptera), the virulence of the GHA strain was similar to virulence in one or more of the Hawaiian strains for each insect species tested. Our data do not support the hypothesis that the GHA strain of B. bassiana represents a greater risk to native insects than the strains already present in Hawaii.