Factors affecting zygosporogenesis in Mucor piriformis and Gilbertella persicaria

Abstract

The effects of four factors, namely temperature, light, pH, and type of medium on zygosporogenesis of Mucor piriformis and Gilbertella persicaria were studied. In addition, the effects of ratios of (+):(-) mating types on zygosporogenesis of M. piriformis were evaluated. For M. piriformis, rich media, temperature lower than 15 C, medium pH of 3.5 to 8, and darkness favored zygospore development. For G. persicaria, rich media, temperature of 20 C, darkness, and medium pH of 4 to 6 favored zygospore development. Zygospores of M. piriformis were not produced when cultures containing pairs of (+) and (-) mating types were continuously incubated at 20 and 23 C for 30 d. However, as many as 6000 zygospores developed when cultures were incubated continuously at 0, 5, 10, or 15 C for 30 d. Optimum temperature for zygospore production was 10 C for M. piriformis and 20 C for G. persicaria. Significantly fewer zygospores of M. piriformis were produced after incubation of cultures 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 temperatures and inhibited by continuous light in M. piriformis. In contrast, zygosporogenesis of G. persicaria was inhibited by low temperatures and significantly reduced by continuous light. Although rich nutrient favored the production of more zygospores than less rich media in both species studied, zygosporogenesis of G. persicaria was less dependent on high nutrients than that of M. piriformis. The numbers of zygospores produced by M. piriformis depended on both total levels of propagules and ratios of (+):(-) mating types.

Key Words:

• Mucoraceae
• postharvest pathogen
• sexualism
• zygospores