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These are lower group of fungi. They are without septate and have coenocytic hyphae. A both sexual and asexual form of reproduction occurs. Asexual reproduction occurs by zoospores and aplanospores. Sexual reproduction occurs by isogamous or heterogamous. This group is sub divided into oomycetes and zygomycetes. Oomycetes is oogamous fungi which is multi nucleate and aseptate. The wall of hyphae contains cellulose and glucans. Asexual reproduction occurs by sporangia which contain spores. Depending on the habitat sporangia produce different spores. In terrestrial they produce conidia and in aquatic conditions it produces zoospores. They have two flagella. One of the flagella is smooth and the other one is tinsel type. Their gametes are without flagella. Sexual reproduction occurs by gametangial contact. It leads to formation of oospores. It includes late blight, white rust, damping and downy mildew. Late blight of potato is caused by phytopthora infestans. They occur on margins as well as on tips of leaflets. Blight denotes to brown and black dead areas. Irish famine occurred due to late blight of potato. White rust causes appearance of white blisters. It is caused by albugo candida. Damping is caused by pythium species. In this seedlings of plants are killed. In downy mildew a cottony bloom on the surface of host occurs. It occurs in cereals and in few plants. It is caused by sclerospora graminicola.

Zygomycetes is also known as conjugation fungi. They are of terrestrial type and are of Saprotrophic type. Their mycelium is multi nucleate and aseptate. Hyphae wall is made up of chitin. They have no motile cells. Spores formed by mitosis are known as sporangiospores. Sexual reproduction occurs by gametengial copulation. It produces a diploid spore known as zygospore. That’s why they are classified as Zygomycetes. They give rise to new sporangium known as germ sporangium which forms meiospores known as germ spores. It includes squirting fungus, rhizopus and mucor. Squirting fungus is a dung mould which throws sporangia. Rhizopus is known as black bread mould. Mucor is also known as dung mould and it is coprophilous. Rhizopus causes soft rot and affects apple, sweet potato etc. Some species of mucor affects internal organs of man. Both of them cause fermentation of alcohol and production of various organic acids.