Abstract:

strains of Metarhizium were cultivated in submerged culture. The results indicated that the submerged conidia could be produced by means of microcyclic sporogenesis for some strains of Metarhizium,but perhaps, the occurrence of microcyclic sporogenesis depended on the nature of strains. Submerged sporulation of M337 strain was emphatically observed in the media containing different nutrient elements. The results showed that the submerged sporulation depended on a delicate equilibrium in the composition of the medium. Various carbon and nitrogen sources affected the production of submerged conidia greatly. Sucrose, soluble starch and lactose were effective for sporulation of submerged conidia. Peanut cake powder, yeast extract and peptone were ideal nitrogen sources for submerged sporulation. The influence of trace elements on submerged sporulation was most spectacular. Molybdenum was the most important element. Zinc was stimulatory. When all 6 elements (B,Cu,Fe,Mn,Mo,Zn) were added together, it yielded highest production of submerged conidia. Vitamins affected submerged sporulation significantly. VB₆+VH and compound vitamin B were more effective for producing submerged conidia. In addition, the infectivity of submerged conidia of M337 strain was tested in laboratory, which showed higher virulent to the 3rd～4th instar larvae of Dendrolimus punctatus. From experiment results, we can appreciate the fact of worth while making a thorough study on production of conidia of Metarhizium cultivated in submerse fermentation.

Key words: Metarhizium, Submerged culture, Submerged conidia, Dendrolimus punctatus, Toxicity