MOLECULAR ANALYSIS OF HYPERVIRULENT SOMATIC HYBRIDS OF THE ENTOMOPATHOGENIC FUNGI BEAUVERIA-BASSIANA AND BEAUVERIA-SULFURESCENS

Protoplast fusion of diauxotrophic mutants of a Beauveria bassiana ent omopathogenic strain (Bb28) and a Beauveria in sulfurescens toxinogeni c strain (Bs2) produced hybrids which were significantly different fro m the parents in pathogenicity, Some of the hybrids were hypervirulent and killed insects more quickly than the Bb28 strain, probably becaus e these hybrids had acquired the toxic activity of the Bs2 strain. By using six nuclear genes and a telomeric fingerprint probe, the molecul ar structures of the hybrids were studied. The results demonstrated th e occurrence of parasexual events, Hybrids appeared to be diploid or a neuploid, with portions of the genome being heterozygous. A mitochondr ial molecular marker indicated homoplasmy of the hybrids and inheritan ce of mitochondria from strain Bs2 or Bb28, The pathogenicities and th e ploidies of the hybrids remained stable after passage through the ho se insect, showing that somatic hybridization provides an attractive m ethod for the genetic improvement of biocontrol efficiency in the genu s Beauveria.