Submitted to: World Journal of Microbiology and Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/19/2002
Publication Date: 6/15/2003
Citation: Vega, F.E., Jackson, M.A., Mercadier, G., Poprawski, T. 2003. The impact of nutrition spore yields for various fungal entomopathogens in in liqiud culture. World Journal Of Microbiology And Biotechnology. Interpretive Summary: In order to enhance the efficacy of insect pathogenic fungi as biological control agents, it would be useful to improve production systems for generating large numbers of fungal spores. Six strains of fungal insect pathogens, including Beauveria bassiana, Paecilomyces fumosoroseus, and Metarhizium anisopliae were grown in liquid media providing different nutritional conditions to determine if high concentrations of stable spores could be produced. A Paecilomyces fumosoroseus strain isolated from the coffee berry borer was shown to possess the production and stabilization attributes required for commercial development. This was based on the high yields obtained in some of the tested media, and the high mortality on silverleaf whiteflies, a serious agricultural pest of more than 500 species of plants, after spraying fresh and air dried spores. Our results will contribute to the development of new high yielding production systems for fungal insect pathogens. The results suggest that screening potential fungal biopesticides for amenability to liquid culture spore production can aid in the identification of commercially viable isolates.
Technical Abstract: Spore yields were measured for various fungal entomopathogens (two Beauveria bassiana strains, three Paecilomyces fumosoroseus strains and one Metarhizium anisopliae strain) grown in six nutritionally different liquid media. In general, highest spore yields were obtained in media containing 36 g/L carbon and a carbon to nitrogen ratio of 10:1. After four days growth, highest spore yields were obtained in the three Paecilomyces strains. Using commercial production protocol, a comparison of spore yields for a coffee berry borer-isolated P. fumosoroseus strain and a commercial B. bassiana strain showed those highest spore concentrations were obtained with the P. fumosoroseus strain 2-days post inoculation. Desiccation studies showed that ca. 80% of the liquid culture produced P. fumosoroseus spores survived the air-drying process. The virulence of freshly-produced, air-dried and freeze-dried coffee berry borer P. fumosoroseus blastospores preparations were tested against silverleaf whiteflies. While all preparations infected and killed B. argentifolii, fresh and air-dried preparations were significantly more effective.