Zygomycota,zygomycota reproduction cycle,zygomycota reproduction,zygomycota definition

Zygomycota contains fungi informally called zygomycetes.

Most live on decaying plant and animal matter in the soil; a few are parasites of plants, insects, and animals, including humans.

 The hyphae of zygomycetes are coenocytic, with many haploid nuclei. Asexual spores develop in sporangia at the tips of aerial hyphae and are usually wind dispersed. Sexual reproduction produces tough, thick-walled zygotes called zygospores that can remain dormant when the environment is too harsh for growth of the fungus.

The mold Rhizopus stolonifer is a common member of this division. This fungus grows on the surface of moist, carbohydrate-rich foods, such as breads, fruits, and vegetables. 

Hyphae called rhizoids extend into the bread and absorb nutri­ents. Other hyphae (stolons) become erect, then arch back into the substratum, forming new rhizoids.

Still others remain erect and produce at their tips asexual sporangia filled with black spores, giving the mold its characteristic color. Each spore, when liberated, can germinate to start a new mycelium.

Rhizopus spp.  usually  reproduce asexually,  but if  food be­comes scarce or environmental conditions unfavorable, sexual reproduction occurs . Sexual reproduction requires compatible strains of opposite mating types. When the two mat­ ing strains are close, each produces a different hormone, called a pheromone, that causes their hyphae to form projections called progametangia; these mature into gametangia.

 After fusion of the gametangia, the nuclei of the two gametes fuse, forming a zygote.

 The zygote devel­ops a thick, rough, black coat and be­ comes a dormant zygospore.

Meiosis often occurs at the time of germination; the zygospore then splits open and pro­duces a hypha that bears an asexual spo­rangium to begin the cycle again.

One member of the genus Rhizopus is important because it is involved in the rice disease known as seedling blight. 

If one considers that rice feeds more people on Earth than any other crop, the impli­ cations of this disease are obvious. it was thought that the fungus secreted a toxin that kills rice seedlings, so scientists set about isolating the toxin and the genes that produce it. 

Much to everyone's sur­prise, an a-proteobacterium, Burkholde­ ria sp. found growing within the fungus produces the toxin.

Zygomycetes also contribute to hu­man welfare. 

 For example, one species of Rhizopus is used in Indonesia to produce a food called tempeh from boiled, skinless soybeans. 

Another zygomycete (Mucor spp.) is used with soybeans in Asia to make a curd called sufu.

Others are em­ployed in the commercial preparation of some anesthetics, birth control agents, in- dustrial alcohols, meat tenderizers,  and the yellow coloring used in margarine and butter substitutes.