The Effects of Culture Medium Quality and Host Passage on Zoosporogenesis, Oosporogensis, and Infectivity of Lagenidium Giganteum (Oomycetes: Lagenidiales)
Journal of Invertebrate Pathology
Two isolates of Lagenidium giganteum, LGC from California and LGL from Louisiana, progressively lost the ability to form oospores and zoospores and to infect Aedes aegypti larvae, after prolonged culture on sterol-free PYG agar medium (peptone, yeast extract, glucose). Reductions in zoosporogenesis and infectivity reached statistically significant levels by 15 weeks, relative to values for fungus maintained in sterol-containing liquid Z medium (hemp seed extract, wheat germ, yeast, glucose), with and without periodic passages through host mosquitoes. Twenty weekly subcultures in Z medium of LGC attenuated on PYG medium did not signficantly restore its ability to produce zoospores or infect mosquitoes and raised the frequency of occurrence of oospores in infected larvae by only 9%. Fifteen serial passages through host mosquitoes fully restored the vigor of LGC in terms of oosporogenesis, zoosporogenesis, and infectivity. Assays on 23 randomly taken single-zoospore isolates of attenuated LGC and assays on 6 single-zoospore isolates taken 6 h after suspension of mycelium, or 6 single-zoospore isolates taken 6 days after suspension, gave no indications of genetic heterogeneity from which vigorous strains could be chosen. It is suggested that loss and recovery of vigor is due to the availability of sterols.
Lord, J.C. and D.W. Roberts. 1986 The effects of culture medium quality and host passage on zoosporogenesis, oosporogenesis, and infectivity of Lagenidium giganteum (Oomycetes: Lagenidiales). J. Invertebr. Pathol. 48:355-361.