PRODUCTION OF PAECILOMYCES-FUMOSOROSEUS CONIDIA IN SUBMERGED CULTURE

Mexican isolates of Paecilomyces fumosoroseus (Wize) Brown & Smith vir ulent to nymphs and adults of Bemisia tabaci Gennadius (Homoptera: Ale yrodidae) were screened in terms of spore production in submerged cult ure. Effects of light, temperature stress and yeast extract on sporula tion were studied. Cycles of 12 hours light/12 hours dark increased sp ore production as well as an incubation for 24 hours at 37 degrees C p rior to incubation at 30 degrees C. Ln absence of organic nitrogen bot h fungal growth and sporulation were very low. Spore production in fer menters with a culture media of a C:N ratio of 25 was doubled as compa red to a media with a C:N ratio of 11. Both conidia and blastospores w ere produced. Production of conidia directly from blastospores through microcyclic sporulation was observed. The proportion of conidia obtai ned under optimal conditions was 88.8%. Submerged culture of P. fumoso roseus seemed advantageous compared to rice-filled plastic bags produc tion method because of shorter fermentation times, higher spore yields and substantially higher volumetric spore productivity. Results indic ated that careful manipulation of nutritional and environmental condit ions allowed for production of conidia during submerged growth of P. f umosoroseus, microcyclic sporulation being induced under a set of envi ronmental conditions including temperature stress and nutrients limita tion.