FACTORS AFFECTING ZYGOSPOROGENESIS IN MUCOR PIRIFORMIS AND GILBERTELLA-PERSICARIA

The effects of four factors, namely temperature, light, pH, and type o f medium on zygosporogenesis of Mucor piriformis and Gilbertella persi caria were studied. In addition, the effects of ratios of (+):(-) mati ng types on zygosporogenesis of M. piriformis were evaluated. For M. p iriformis, rich media, temperature lower than 15 C, medium pH of 3.5 t o 8, and darkness favored zygospore development. For G. persicaria, ri ch media, temperature of 20 C, darkness, and medium pH of 4 to 6 favor ed zygospore development. Zygospores of M. piriformis were not produce d when cultures containing pairs of (+) and (-) mating types were cont inuously incubated at 20 and 23 C for 30 d. However, as many as 6000 z ygospores developed when cultures were incubated continuously at 0, 5, 10, or 15 C for 30 d. Optimum temperature for zygospore production wa s 10 C for M. piriformis and 20 C for G. persicaria. Significantly few er zygospores of M. piriformis were produced after incubation of cultu res continuously at 15 C than at 0, 5, or 10 C with or without 2-d of preincubation at 20 C. Zygosporogenesis was favored by low temperature s and inhibited by continuous light in M. piriformis. In contrast, zyg osporogenesis of G. persicaria was inhibited by low temperatures and s ignificantly reduced by continuous light. Although rich nutrient favor ed the production of more zygospores than less rich media in both spec ies studied, zygosporogenesis of G. persicaria was less dependent on h igh nutrients than that of M. piriformis. The numbers of zygospores pr oduced by M. piriformis depended on both total levels of propagules an d ratios of (+):(-) mating types.