CERCOSPORA - CLASSIFICATION, VEGETATIVE STRUCTURE, REPRODUCTION

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            A. CLASSIFICATION:
Division – Mycota
            Sub-division – Eumycotina
                        Class – Deuteromycetes
                                    Order – Moniliales
                                                Family – Dematiaceae
                                                            Genus – Cercospora
            The genus Cercospora includes about 3800 species. Majority of the species are plant pathogens which cause leaf spot diseases of higher plants of economic value. Commonly the leaf spot disease is called the tikka disease. C. personata and C. arachidicola are of two commonly known form-species which is responsible for the leaf spot disease of groundnut.
            B. STRUCTURE OF THE VEGETATIVE BODY:- The mycelium in many species (C. personata) is entirely internal. The hyphae ramify in the intercellular spaces between the mesophyll cells of the host leaf obtaining nutrition by sending branched haustoria into the spongy and palisade cells. In some form species (C. arachidicola) the mycelium consists of both external and internal hyphae. The later in the beginning are intercellular but later on become intracellular. They do not produce haustoria. Before the mycelium enters the reproductive phase, the hyphae accumulate and become compacted to form brown to black globular mass of hyphae, the stroma immediately beneath the epidermis of the host leaf in a sub-stomatal cavity.
            C. REPRODUCTION:- The perfect stage in Cercospora is rare. However, perfect stage is observed in C. personata and C. arachidicola. It is Microsphaerella berkleyi in the former.
            Reproduction generally takes place by means of long, cylindrical, usually hyaline, multiseptate conidia, which are produced at the tip of unbranched, dark conidiophores. The later arise in tufts from a stroma lying in a sub-stomatal cavity and emerge by rupturing the overlying epidermis. The conidiophores are geniculate (knee-jointed) and 1-2 septate. The conidium, as it falls off leaves a scar on the conidiophore.

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