In this article we will discuss about:- 1. Genus of Cercospora 2. Mycelium of Cercospora 3. Reproduction.
Genus of Cercospora:
The form-genus Cercospora includes about 3,800 form-species. Majority of them are plant pathogens which cause leaf spot diseases of higher plants of economic value (Fig. 16.11 A).
Commonly the leaf spot disease is called the tikka disease. C. personata and C. arachidicola are the two commonly known form-species which are responsible for the leaf spot (tikka) disease of groundnut (Archis hypogea).
Mycelium of Cercospora:
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 latter 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 substomatal cavity (Fig. 16.11 B).
Reproduction in Cercospora:
Asexual reproduction (Fig. 16.11 B-C):
It takes place by means of long, cylindrical usually hyaline, multiseptate conidia (C) which are abstricted successively at the tips of unbranched, dark conidiophores (B).
The latter arise in tufts from a stroma lying in a substomatal 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.
The perfect stage of both C. personata and C. arachidicola is known. It is Microsphaerella berkleyi in the former.