Sensitivity ofBeauveria bassiana to solanine and tomatine : Plant defensive chemicals inhibit an insect pathogen

The alkaloids solanine and tomatine and the polyene antibiotic nystatin were tested in vitro against the entomopathogenic fungusBeauveria bassiana. Nystatin was the most inhibitory compound tested, reducing colony formation, growth, and development of conidiaphores to a greater degree and at lower concentrations than the alkaloids. Tomatine inhibited colony formation and growth more than solanine, which had relatively little effect on the fungus. The toxicity of tomatine suggests that germination of conidia and subsequent hyphal growth would be inhibited when an insect consumes conidia along with foliage containing 0.100 mg/g (fresh weight) of this compound. The sensitivity ofB. bassiana to alkaloids appears to be in the middle of the range found with other fungi.