Question

The correct condition among the following with reference to sexual reproduction in Rhizopus stolonifer is
A)′+′×′−′= zygospore
B)′+′×′−′= No zygospore
C)′−′×′−′= zygospore
D)′+′×′+′= zygospore

Answer 1

A zygospore is a diploid replication process in the life cycle of many fungi and protists. Zygospores are formed by the nuclear fusion of haploid cells. In case of fungi, the zygospore formation takes place are called as zygosporangia, this happens when fusion of budding structures takes place. This can occur in mycelia having similar (in homothallic fungi) or of different mating types (in heterothallic fungi).

Complete answer:
Rhizopus is a genus of modern plant saprophytic fungi and specialized animal parasites. Rhizopus stolonifer is used commercially for the manufacture of alcohol and organic acids. By developing asexual and sexual spores, they replicate. In sexual reproduction, following gametangial fusion, a dark zygospore is formed. The only diploid process of reproduction of Rhizopus stolonifer are the zygospores. They are made up of two suspensor cells, or hyphae, which are the progametangia. In both sides of the spore, suspensor cells are present to provide protection. The zygospore forms from two unique haploid hyphae with opposite styles of mating (+ and - or male and female gametangia) that meet and are in close proximity to each other because of hormones. Sometimes known as plasmogamy, the two cytoplasm intermingle.

Hence, the correct answer is option (A)

Note: Rhizopus stolonifer can asexually and sexually reproduce. That is a genus that is heterothallic. When compatible mating strains are combined, sexual reproduction occurs, eventually giving birth to zygospores. The sporangiophore comprises mating type strains of both '+' and '-'. Meiosis is postponed until the zygospores germinate. Regardless of the type of mating, the gametogenia also varies in size. This size difference is not due to sex, but to diet, probably.