38th Annual Meeting of the Society for Invertebrate Pathology

Mass-produced biocontrol agents Mycotal and Vertalec have a high virulence against whitefly and aphid, respectively. Strain B-2 has a higher colonizing ability on a cucumber leaf as an epiphyte(Koike et al. 2004). In this study, we performed protoplast fusion experiment among 3 strains of Verticillium lecanii to breed useful new strains those had useful characteristics as biological control agents. Nit mutant was applied as a genetic marker, in order to visualize a colony that had undergone fusion. Complementary parental protoplasts were mixed, and fused by PEG method. 126, 44 and 4 hybrid strains were detected from combination of Vertalec×Mycotal, B-2×Mycotal and B-2×Vertalec, respectively. Furthermore we observed vigorous and vertical growth colonies among them, and measured colony growth speed and the amount of the spore production. Some of them showed rapid growth when compared to parental isolates. It indicated that such vigorous growth might be an important factor to improve the virulence. It also showed that the protoplast fusion could be an effective methods to breeding the entomopathogenic fungi. We also report screening of virulence to aphid and whitefly.