Natural populations of the entomopathogenic fungus Beauveria bassiana in Chinese forest ecosystems are diverse and reveal equal frequencies of mating types within phylogenetic species

Beauveria bassiana is an important entomopathogenic fungus with widespread application in the biological control of harmful insect pests. This species is widely distributed as an anamorph while only two teleomorph specimens have been found in eastern China. However, little is known about the ecological conditions for sexual reproduction in natural populations of B. bassiana. Here, we collected 488 isolates of Chinese B. bassiana sensu stricto from five sites, in which teleomorph or anamorph occurred, and used molecular phylogenetic and haplotype information to determine phylogenetic diversity, mating types, and sexual reproductive potential in these populations. Molecular identification based on denaturing gradient gel electrophoresis (DGGE) and combined data of the nuclear intergenic region Bloc and translation elongation factor-1a (TEF) assemblage resolved five B. bassiana s.s phylogenetic species labeled according to their geographic origin: Europe/N. Africa 1, Asia 3, Asia 4, AFNEO_1, and N. America 2. In Guniujiang and Manshuihe collection sites, teleomorph isolates RCEF 0771 and RCEF 0382 were both identified as Europe/N. Africa 1 phylogenetic species. In addition, more than half of the isolates in five representative sites belonged to Europe/N. Africa 1. However, the teleomorph of B. bassiana s.s. was not detected in Kuankuoshui while isolates within Europe/N. Africa 1 were present at this site, and isolates belonging to Europe/N. Africa 1 were not found in either Jingyuetan or Dinghushan collection sites. Distribution of MAT1 and MAT2 mating type idiomorphs in Europe/N. Africa 1 were 51:69, 37:24, and 15:15 in Guniujiang, Manshuihe, and Kuankuoshui, respectively. The presence of teleomorph and roughly equal frequencies of opposite mating types indicate regular sexual reproduction in B. bassiana natural populations. The data offer a better understanding of the ecological conditions of sexual reproduction in natural populations of B. bassiana. These results also yield insights into the potential for sexual reproduction in other supposedly ‘asexual’ fungi.