Microsclerotia production by Metarhizium spp.

The entomopathogenic fungi, especially Metarhizium, Beauveria e Isaria, are the pathogens most used for biological control of pests. In appropriate nutritional and physical conditions the fungi of the genus Metarhizium form an structure of resistance called microsclerotium. Conidia produced by microsclerotia are infective propagule to soils insects. The commercial interest in the use of this propagule to control soil pests has increased with the discovery that some isolates of Metarhizium produce microsclerotia in submerged fermentation. The source and/or concentration of the nitrogen and carbon components of the medium can have a dramatic impact on fungal propagule form and yield. The aim of this study was to evaluate carbon and nitrogen sources for microsclerotia of two Metarhizium spp. isolates (Metarhizium robertsii and Metarhizium sp. Indeterminate). In this work was used culture medium for microsclerotia production contained carbon and nitrogen source in carbon:nitrogen ratio (C:N) of 50:1. The results showed an improvement in terms of microsclerotia production compared with the culture medium originally used, this increase was from 13000 MS. mL-¹ to 26000 MS. mL-¹ for Metarhizium robertsii, and 11000 MS. mL-¹ to 19000 MS. mL-¹ for Metarhizium sp. indeterminate.