Cercospora
Cercospora:-
1. Classification:-
Kingdom:- Myceteae
Division:- Amastigomycota
Sub division:- Deuteromycotina
Class:- Deuteromycetes
Sub-class:- Hyphomycetidae
Order:- Moniliales
Family:- Dematiaceae
Genus:- Cercospora
2. Habit and Habitat:-
> Cercospora is a very large genus of family Dematiaceae. It includes about 3800 form-species.
> Majority of the species are parasitic and cause leaf spot or tikka disease of economically important plants.
> C. apii is a human pathogen and may cause several lesions on the face.
> The infection begins as pale green spots on the upper surface of the leaf.
> These spots gradually enlarge, turn brown in colour and ultimately entire leaf dries and crumbles down.
3. Thallus structure:-
> The mycelium is well developed, branched, intercellular and septate.
> The hyphae when young are hyaline but later turn brown.
> Intercellular hyphae produce lobed haustoria.
> In C. arachidicola the mycelium is both external and internal and becomes intracellular after the death of the host cells.
> At maturity some of the hyphae aggregate to form brown to black colour globular mass in the sub-stomatal cavity or beneath the epidermis of the host leaf. It is called stroma (plural. stromata).
4. Reproduction:-
> Cercospora reproduces only by means of conidia.
> A tuft of conidiophores emerge either through stomata or ruptured epidermis.
> Conidiophores are hyaline to dark brown, septate or aseptate, straight or flexuous and show distinct geniculate (knee like) bends.
> Each conidiophore forms single conidium acrogenously at its apex.
> The growth of the conidiophore is renewed after the formation of first conidium.
> The mature conidium is pushed aside due to sub-apical growth of the conidiophore.
> On detachment each conidium leaves a geniculate scar or conidial scar on the conidiophore at the place of its attachment.
> Conidia are long cylindrical, obclavate, multi-septate (tranverse septa), hyaline or brownish in colour. They vary in size but always have a breadth, length ratio of 1: 10 − 1: 150.
> The conidia are disseminated by wind or rain splash.
> Under suitable conditions (24-28°C temperature) conidia germinate by giving rise to one or more germ tubes.
> Each germ tube develops into a new mycelium.
> The perfect stages of C. arachidicola and C. personata are Mycosphaerella arachidicola and M. berkeleyii respectively.
5. Diseases Caused by Cercospora:- Some important diseases caused by cercospora are as follows:
i. Leaf spot or Tikka disease of ground nut:- C. arachidicola, C. personata
ii. ‘Sigatoka’ leaf-spot disease of banana:- C. musae
iii. ‘Frog-eye’ leaf-spot of tobacco:- C. necotinae
iv. Leaf-spot disease of lady’s finger:- C. hibiscus
v. Leaf-spot disease of cajanus cajan:- C. indica
vi. Leaf-spot disease of cotton:- C. gossypina
vii. Leaf-spot disease of rice:- C. oryzae.