Germination of Zygospores of Mucor piriformis (On the Life History of Mucor piriformis)

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Abstract
A technique for germinating zygospores of Mucor piriformis is described. Zygospores were produced by mating compatible strains on acidified potato-dextrose agar. Strips of agar with zygospores facing upward were placed on sterile filter paper in Petri dishes at room temperature (23 .+-. 1 C). Petri dish lids were left offset 1 cm and the agar allowed to dry slowly for 5 days. Once dried, the agar strips bearing zygospores were washed with sterile water to remove contaminating sporangiospores. Excess water was removed with paper towels and the agar strips were incubated at room temperature in the same closed Petri dishes. Zygospores germinated in 2-3 da at 23 C and germination continued when the spores were transferred to 0 C. The majority (> 95%) of germinated zygospores developed one germ-sporangiophore. Of the germ-sporangia tested, 95.6% yielded only + mating-type germ-sporangiospores, 2.2% yielded only -, and 2.2% yielded both + and -. Zygospores formed on artifically inoculated peach and nectarine fruit germinated and produced 95.8% + and 4.2% - germ-sporangia. The results indicated lack of adherence to expected Mendelian ratios. In surveys of orchards in the Hood River Valley, Oregon, [USA], zygospores were found on 1.6% of pear fruits infected naturally by M. piriformis. The significance of these findings in the life cycle of M. piriformis is discussed.