EFFECTS OF NUTRIENTS ON COLONY FORMATION, GROWTH, AND SPORULATION OF METARHIZIUM-ANISOPLIAE (DEUTEROMYCOTINA, HYPHOMYCETES)

In order to examine some possible effects of plant root exudates on Metarhizium anisopliae, we examined the effects of a range of carbon and nitrogen sources and vitamins on colony formation, mycelial growth, and sporulation of two isolates (EF25 and EF55). We also hoped to provide some information relevant to culturing and production methods for M. anisopliae. Colony formation was inhibited by sorbose on a KNO3-based agar medium, but not other carbohydrates. On agar media, sorbose caused abnormal growth and inhibited sporulation by;both isolates. All other carbohydrates, but especially soluble starch and mannose, supported growth and sporulation. Oxalic, sorbic, and tartaric acids prevented colony formation. Acetic, citric, and malic acids reduced growth, and acetic and malic acids reduced sporulation. Soy peptone was much better than all simple nitrogen compounds for growth and sporulation. L-glutamine, L-serine, L-asparagine, L-alanine, and KNO3 were best for growth, and L-cysteine, L-aspartic acid, NH4NO3, and L-threonine were the worst. (NH4)(2)SO4, L-lysine, and L-threonine were best for sporulation. Neither isolate sporulated on L-cysteine, L-glutamine, or L-leucine and little or no sporulation occurred on L-alanine and L-serine. Pyridoxine HCl reduced the growth of EF25, and biotin, pyridoxine, and riboflavin reduced sporulation. Pyridoxine HCl reduced the growth of EF55. Various carbohydrates and nitrogen compounds in plant root exudates could cause premature germination in soil, resulting in loss of inoculum. Organic acids might have the opposite effect, contributing to persistence of conidia in soil, but potentially preventing germination on hosts. Soluble starch may be a useful carbon source for use in production media. (C) 1995 Academic Press, Inc.