GENETIC-IMPROVEMENT OF HEAT TOLERANCE IN HETERORHABDITIS-BACTERIOPHORA THROUGH HYBRIDIZATION

A trait for heat tolerance was transferred from the IS5 strain to the HP88 strain of Heterorhabditis bacteriophora Poinar. The transfer was accomplished by allowing the heat tolerant strain (IS5) to mate with t he commercial strain (HP88). The hybrid nature of the progeny was conf irmed using a marker mutant of the HP88 strain (Hp dpy-2) and by backc rossing. Progeny from the cross were screened for heat tolerance by me asuring survival after 2 h exposure to 40 degrees C. After three and s ix passages through Galleria mellonella (L.), survival of hybrid nemat odes was significantly greater than survival of the HP88 strain and wa s similar to the survival of the IS5 strain. Fitness, in terms of viru lence, reproduction and storage capacity was compared among the IS5, h ybrid, and HP88 strains. At 32 degrees C, the IS5 and hybrid strains c aused mortality of G. mellonella at a faster rate than the HP88 strain . Similar to the IS5 strain, the hybrids exhibited sensitivity to cold . After 1 week of storage at 10 degrees C, the survival of the hybrid and IS5 strains was significantly reduced relative to the HP88 strain. No differences were detected in reproductive potential among the stra ins. This study demonstrates the potential of using hybridization to g enetically improve entomopathogenic nematodes and illustrates the adva ntages of using marker mutations in this endeavor. (C) 1997 Academic P ress.