Ex.No. 3                                              Sexual reproduction in Fungi

Sexual reproduction in fungi results in the union of two different nuclei. The sex organs of fungi are called as gametangia and sex cells are known as gametes. Male gamentagium is called antheridium and female gamentagium is called Oogonium. The process of sexual reproduction involves three phases.

1. Plasmogamy 2. Karyogamy 3. Meiosis                      

Plasmogamy: Fusion of two protoplasm                                                                                        

Karyogamy: Fusion of two nuclei                                                         

 Meiosis: Reduction division                                                                                                                 

Types of Plasmogamy:                                                                                                                                                            Planogametic copulation: Motile gametes are generally called as Planogametes. It involves the fusion of two gametes of which at least one must be motile. Three types of Planogametic copulation: Isogamy, Anisogamy and Heterogamy                                                                

Isogamy: Fusion of male and female gametes is same shape and size (Ex. Synchytrium sp.)

Anisogamy: Fusion of male and female gametes is morphologically similar but different in size. Ex. Allomyces.

Heterogamy: Fusion of male and female gametes is different size and shape (Ex. Many higher fungi)         Gametangial contact: This involves fusion of two gametangia which are morphologically different with undifferentiated protoplasm, each having one nucleus for fusion though may come in contact with each other. Ex. Through pore / hole : Pythium; Through fertilization tube: Ascomycetes                           

Gametangial copulation: The difference from the gametangial contact lies in only passing the entire contents of one gametangium to another gametangium instead of passage of only the nuclei. It occurs in two ways. Ex. Chytridiomycetes                                                                           

Spermatization: Puccinia fungi produce numerous, non motile Uninucleate spore are called Spermatia. They are behaving like male gametes and fusion with female gametes namely receptive hypha. 

Somatogamy: Fusion between somatic cells is called Somatogamy. Ex. Ascomycetes    

Sexual spores of fungi    : 1. Diploid resting spore (Ex. Oospore, Zygospore); 2. Haploid non resting spore (Ex. Ascospore, Basidiospore)      

Oospore: Oomycetes class of fungi producing sexual spore is called as Oospore. They are orange yellow colour, double celled, thick walled, resting spore and diploid. The outer most wall is called as exine and inner most wall is called as intine with a central oil globule. Ex. Pythium, Phytophthora

Zygospore: Zygomycetes class of fungi producing sexual spore is called as Zygospore. They are diploid, black in colour, spherical and resting spore. Ex. Rhizopus

Ascospore: Ascomycetes class of fungi producing spore is called as ascospore. They are hyaline, haploid and non resting spore. It is generally born in a specialized sexual structure called as ascus. Ascus is a bag like structure which contains eight number of ascospore. Ex. Erysiphe                                                          Basidiospore: Basidiomycetes class of fungi producing sexual spore is called as Basidiospore. They are hyaline and haploid non resting spore. It is generally born in a specialized sexual structure called as Basidium. Basidium is a club shaped with four sterigma (sterigmata – supporting organ) on which four basidiospores are produced. Ex. Mushroom

Sexual fruiting bodies of fungi:  Ascocarp and Basidiocarp

Ascocarp / Ascoma: Ascomycetes class of fungi producing sexual spore is called ascocarp. Types of ascocarp are Cleistothecium, Perithecium, Apothecium and Naked Asci. 

Cleistothecium: It is a globose, completely closed ascocarp in which asci are arranged. The fruiting body wall is called peridium consists of pseudoparenchymatous and the outer hyphal growth called mycelial appendages. Ex. Erysiphe                                                                                                                  

Perithecium: It is a flask shaped structure which consists of narrow opening called ostiole. Perithecium consists of periphysis and paraphysis. Periphysis is the short hair on the side of ostiole. Paraphysis is a sterile hair arises in between ascus. Ex. Claviceps                                    

Apothecium: It is an opened ascocarp. It is a saucer shaped and arrangements of asci are called as hymenium.  Ex. Peziza sp.                                                                                                                                         Naked asci: There is no fruiting bodies are formed. Only ascus or asci are formed on the epidermal cells of the host. Ex. Taphrina deformans

Basidiocarp / Basidioma: Basidiomycetes class of fungi producing sexual fruiting body is known as Basidiocarp. Basidium is a sexual structure of Basidiomycetes, which contains four basidiospores. Ex. Mushroom