Published online by Cambridge University Press: 31 May 2012
Enhancement of virulence in entomogenous fungi has been a particularly neglected area of research (Roberts and Yendol 1971). It is generally believed that virulence increases following successive passage through a host and decreases following repeated subculturing on artificial media (see Aizawa 1971; Roberts and Yendol 1971). Using single-spore isolates (clones) of Beauveria bassiana (Bals.) Vuill., SamšiňSáková and Kálalová (1983) demonstrated spontaneous mutants with increased virulence. Enhancement of virulence using parasitic selection pressures has been accomplished by passage of fungal strains through a host (Daoust and Roberts 1982; references in Ignoffo et al. 1982). Such changes are thought to be due to gradual selection of genotypes.