Factors Influencing Zoospore Production in Liquid Cultures of Lagenidium giganteum (Oomycetes, Lagenidiales)

Abstract

A procedure is described for producing large numbers of zoospores in liquid cultures of mosquito-parasitizing fungus Lagenidium giganteum. The fungus was grown 4–6 da on a peptone, yeast extract and glucose medium, transferred to a medium of hempseed extract, wheat germ, yeast extract and glucose, propagated for 4–6 da, then washed and transferred to water. Zoospore production at 25 ± 1 C began at 18 h, peaked between 25–28 h, and ceased at 36 h. Fungus grown in the peptone medium for 4–6 da, and then transferred to hempseed medium and grown for 6 da, produced 13,700-21,000 zoospores per ml, whereas fungus grown 7 da in peptone medium and 6 da in hempseed medium produced 6100 zoospores per ml. Zoospore production occurred at a temperature range of 17–28 C with the optimum for production at 25–28 C. Effects of pH and buffers on zoospore production were studied. An LD50 of 1400 zoospores per ml was obtained with second instar larvae of Culex quinquefasciatus.