The union of two gametes of different nature in terms of size, shape and structural characteristics is called anisogamy.

The union of two gametes of the same nature in terms of size, shape and structure is called isogamy.

1. Combination of gamete: Sexual reproduction of fungi occurs through the union of two gametes. This is done in three ways. Sexual reproduction by the union of gametes is-
(i) Isogamy : The union of two gametes of the same nature in terms of size, shape and structure is called isogamy.
(ii) Anisogamy : The union of two gametes of different nature in terms of size, shape and structural characteristics is called anisogamy.
(iii) Oogamy : The process of sexual reproduction in which a small and motile pongygamete unites with another large and immobile female gamete is called oogamy.
2. Combination of gametangia : Two gametangia of fungi of opposite sex come close to each other and complete sexual reproduction by joining. In this case, the genitals lose their respective properties. Such as Mucor, Rhizopus, Yeast etc.
3. Touch of gametangia: Two gametangia of the opposite sex of the fungus touch each other and the wall of the contact area dissolves to form a duct. Through this duct the male gamete joins the female gamete. In this case, the genitals do not lose their respective properties. Such as Saprolegnia, Pythium, Phytophthora etc.
4. Spermatization: Fertilization unit called spermatium is formed in some fungi. They are small, unicellular and have one nucleus. The spermatozoa come into contact with the female genitalia through water, air or insects and the wall of the contact site dissolves to form a pore. Through this pore the protoplast of the spermatium unites with the protoplast of the female genitalia. eg Puccinia.
5. Somatogamy: Somatogamy in advanced fungi behaves like genitalia and their protoplasts fuse. This is called somatogamy. Somatogamy results in a dikaryotic condition. For example, Aspergillus
6. Parasexuality: If plasmogamy, karyogamy and meiosis do not occur sequentially in the sexual reproduction of fungi, it is called parasexuality or pseudosexuality. Such intercourse is called a parasexual cycle.

Some fungi produce teleutospores that are dark brown or brown in color and are two-celled, ovoid and binucleate. Each spore is covered by a two-layered coat. Each spore germinates in a suitable environment to form a new mycelium. eg Puccinia

Some fungi produce reddish or orange-red unicellular, spherical and binucleate uredospores. Each spore is covered by a two-layered coat. It germinates in favorable environment and forms new mycelium. eg Puccinia

Basidiospores are produced at the tip of the basidium of fungi of the order Basidiomycota. New mycelium is formed from these spores. Eg Agaricus, Puccinia, Ustilago etc.

Spores of fungi of the class Ascomycetes are called ascospores. These spores germinate and form new mycelium. Eg- Saccharomyces, Ascobolus etc.

In unfavorable environment hyphae of some fungi are divided into small segments by forming a wide wall. The protoplast of each segment becomes a chlamydospore enveloped by a thick wall. Chlamydospores germinate and form small hyphae. For example – Fusarium, Mucor, Phytophthora.

Fungal hyphae may divide into two or more segments by a septate wall. Each segment is called oidea or arthronucleus. Oodia germinate in suitable environment to form new mycelium. Such as Coprinus, Rhizopus, Mucor etc.

Spherical or ovoid conidia are produced at the tip of the conidiophore of the fungus. It can form singly or in groups like chains. The mature conidia germinate and form new mycelium. Such as Penicillium, Aspergillus, Phytophthora, Helminthosporium, Alternaria etc.