BASIDIOMYCOTINA AND ITS CLASSIFICATION Dr. Vishnupriya Sharma Department of Botany B.Sc sem II, paper 2,Course code 2BOT T2 Title of the Paper- Mycology and Phytopathology Basidiomycotina Diagnostic features of Basidiomycotina 1. Basidiomycotina comprise of about 550 genera 15,000 species 2.Many of them are saprophytes while others are parasitic. These includes mushrooms, toad stools, puff balls, stink horns, shelf fungi, bracket fungi, rusts, and smuts. 3.They have Septate mycelium ,non motile spores and are characterised by the production of a club-shaped structure, known as Basidium 4. Basidium is a cell in which karyogamy and meiosis occurs. However, the basidium produces usually four spores externally known as basidiospores Vegetative structure: The vegetative body is well developed mycelium which consists of septate, branched mass of hyphae which grow on or in the substratum obtaining nourishment from host. Sometimes, a number of hyphae become interwoven to form thick strands of mycelium which are called rhizomorphs. In parasitic species the hyphae are either intercellular, sending haustoria into the cells or intracellular. The colour of the hyphae varies according to the species through three stages before the completion of life cycle. Three stages of development of mycelium The three stages are the primary, the secondary and the tertiary mycelium. The primary mycelium consists of hyphae with uninucleate cells. It develops from the germinating basidiospore. When young, the primary mycelium is multinucleate, but later on, due to the formation of septa, it divides into uninucleate cells. The primary mycelium constitutes the haplophase and never forms basidia and basidiospores. The primary mycelium may produce oidia which are uninucleate spores, formed on oidiophores. The secondary mycelium is composed of binucleate cells and represents dikaryophase in the life cycle. The binucleate condition is attained from the uninucleate condition, a process known as dikaryotisation or diploidisation. The binucleate or secondary mycelium is also known as dikaryon mycelium. The basidiomycetes have a shortlived uninucleate (monokaryotic) stage and a dominant binucleate stage. The binucleate or dikaryotic condition may arise by one of the following ways: 1. by the union of two primary (monokaryotic) hyphae of opposite strains. 2.by fusion between the germ tubes of two basidiospores of opposite strains 3.by conjugation between two secondary basidiospores of opposite strains that are produced by budding of the basidiospores. 4. by the union of basidiospore of one strain with the germ tube of opposite basidiospore. 5. By the union of two infection threads. 6. By the fusion between two basidia formed by germination of small spores of opposite strains. The tertiary mycelium when the secondary mycelium forms complex tissue to develop fruiting bodies or basidiocarp it is called as tertiary mycelium Classification of Basidiomycotina • Ainsworth divided sub- division Basidiomycotina into three classes- 1. Two orders 1.Uredinales -Puccinia Teliomycetes 2.UstilaginalesU- stilago 2. Hymenomycetes 3. Gastromycetes Order-Agaricales A garicus Only those orders and genus are indicated which are in course Class- Hymenomycetes Class-Gastromycetes • Basidiocarp is present • The basidiocarp remain closed until the spores have been released from the basidia. • Class gastromycetes have been divided into following orders- 1 Hymenogastrales 2. Nidulariales(Bird nest fungi)-Genus Cythus 3.Phallales 4.Lycoperdales(puff balls) eg. Lycoperdon 5 Sclerodermatales Dikaryotization/Diplodisation – Primary or monokaryotic mycelium is converted into secondary or dikaryotic mycelium is called as dikaryotization or diplodisation. It can brought about by following methods CLAMP CONNECTION •The secondary dikaryotic mycelium produce structures called as clamp connections. These are the characteristic features of Eubasidiomycetes and were first observed by Hoftman. Its development was first studied by kniep (1915) and Bensaudi (l918). It allows the migration of a nucleus from one cell to the other. The clamp connections formation takes place as follows The two nuclei (+ and -) of the terminal cell of a mature dikaryotic hyphya divides simultaneously(conjugately) into four nuclei. (+, + and , -). Simultaneously, a pouch like outgrowth arises from its wall(Fig. A, B). One of the nuclei of the upper pair passes into the pouch and is cut off from the main cell by a septum at the base of the pouch. It may now be called a clamp cell (Fig. C, D). Simultaneously, one of the nuclei of the lower pair gets separated from its sister nucleus by a transverse wall (Fig. E). At this stage the terminal cell has two nuclei, the cell below it (penultimate cell) has one nucleus, while the fourth nucleus lies in the clamp cell. The clamp cell grows into hook like structure. Its tip bends over and finally fuses with the lateral wall. The walls at the place of contact dissolve and the fourth nucleus passes into the primary penultimate cell (Fig. F). Thus, the clamp cell serves as a by-pass or a bridge to transfer nucleus one cell to the other and is known a clamp Stages of formation of Clamp connection BASIDIUM & BASIDIOSPORES • Basidium – The basidiospores are formed externally on the basidium which is also known as mother cell. Two nucleus are present inside the young basidium which later on fuses . The fusion nucleus divides to form four nucleus which gets converted to basidiospores. The basidiospore develops at the end of the stalk known as sterigma, through which the nucleus passes from the basidium to enter the developing spore. Two successive divisions in the basidium constitute meiosis. In the Homobasidiomycetidae the basidia are without septa, and four spores arise from, or near, the apex of the basidium. In Heterobasidiomycetidae the basidium divides into four cells, each of which gives rise to a single basidiospore. In the Ustilaginales septa may or may not be present in the basidium. Here more than two divisions follow nuclear fusion, and more than 4 basidiospores are produced. In the Ustilaginales and the Uredinales the basidium develops from a thick-walled chlamydospore (brand spore) or teleutospore (teliospore). On the gemination of brand spore or teleutospore the contents extrude out in the form of a thin-walled promycelium or basidium on which the basidiospores are produced. A. Young teleutospore B.mature teleutospore C. germinating teleutospore with young basidium D. germinating teleutospore with basidium and basidiospores (2+ve and 2 – ve basidiospores) Puccinia sp. teleutospores Basidiospores. The basidiospores are unicellular, uninucleate, rounded, or oval and haploid. The basidiospores usually remain assymetrically attached to their sterigmata. They are colourless or pigmented. The pigments may be green yellow, orange, pink, brown or black. They are usually smooth and thick-walled. When a mature spore is about to be liberated, a droplet of water begins to form at its basal end. The droplet gradually enlarges in size, and ultimately the basidiospore is shot off the sterigma. The basidiospores germinate in water by means of germ tubes which later on develop into uninucleate mycelia. Teleutospores, Basidium & Basidiospores ofP uccinia graminis tritici Types of Basidia On the basis of structure and development there are several types of basidia found in Heterobasidiomycetidae and the Homobasidiomycetidae . Fig A showing Stichobasidial type with a cluster of sporidia,Fig B showing Stichobasidial type with separate 4 sporidia,Fig C showing chaistobasidial type, Fig D showing Tuning fork type , Fig E showing Holobasidial Type Basidia of Homobasidiomycetidae • In class Hymenomycetes and Gastromycetes basidia are of different shapes. In Hymenomycetes(E&F) basidia are slender clavate or broadly clavate while in gastromycetes basidia are globular. The diploid nucleus divides twice forming 4 haploid nuclei. Four sterigmata arise from the apex of the basidium and a uninucleate basidiospore is formed on each sterigmata Basidia of Heterobasidiomycetidae. In Ustilaginales and Uredinales, the teliospore is a diploid, thick-walled, probasidium & on germination it gives rise to the basidium or promycelium. Meiosis takes place and four haploid nuclei are formed thereafter the basidium becomes transversely septate and a row of four cells each containing one nucleus is formed. Each nucleus then migrates into a laterally or terminally formed bud, which converts into a basidiospore (fig A). In Ustilaginaceae the primary haploid nuclei within the basidium may continue to divide, and as a result many basidiospores may be produced. Fig A.