Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: 5/23/1996
Publication Date: N/A
Technical Abstract: The entomopathogenic fungus, Paecilomyces fumosoroseus, is known to cause dramatic epizootics in populations of the insect pest, sweet potato whitefly, Bemisia tabaci. Commercialization of P. fumosoroseus (Pfr) as a bioinsecticide requires low-cost methods to produce high numbers of desiccation tolerant blastospores. In this study, we investigated the effect of supplementing a basal salts medium containing glucose as the carbon source with 13 separate amino acids, 4 separate trace minerals and a mixture of vitamins on growth, sporulation and spore survival after freeze-drying. Poorest growth (3-4 mg biomass/ml, 3-4 x 10**7 blastospores/ml) was observed in Pfr cultures supplemented with methionine, isoleucine, valine or threonine, while aspartate and glutamate supported high concentrations of biomass (14-16 mg/ml) and spores (2-3 x 10**8 blastospores/ml). Using glutamate as the nitrogen source, P. fumosoroseus was able to grow and sporulate in media deficient in cobalt, iron or manganese. Zinc deficiency significantly reduced biomass production (<4 mg/ml) and sporulation (<1.6 x 10**7 blastospores/ml). When Pfr blastospore suspensions in spent medium were freeze-dried, no significant difference in survival (~75%) was seen in blastospores produced in media with glutamate and trace metals, or with Casamino acids and trace metals (standard medium). When Pfr blastospores were rinsed with water, Casamino acids-grown blastospore survival was poor (9%), compared to glutamate-grown blastospore survival (46%). Survival was restored to 75% when blastospore pellets were resuspended in a glucose solution at the same concentration as in the spent medium.