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In this article we will discuss about Cercospora. After reading this article you will learn about: 1. Habit and Habitat of Cercospora 2. Symptoms of Cercospora 3. Vegetative Structure 4. Reproduction 5. Diseases Caused.
Contents:
- Habit and Habitat of Cercospora
- Symptoms of Cercospora
- Vegetative Structure of Cercospora
- Reproduction of Cercospora
- Diseases Caused by Cercospora
1. Habit and Habitat of Cercospora:
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.
2. Symptoms of Cercospora:
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 (Fig. 1 A).
3. Vegetative Structure of Cercospora:
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 (pi. stromata).
4. Reproduction in Cercospora:
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 (Fig. 1 B, C).
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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 (Fig. 1 D). 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:
Leaf spot or Tikka disease of ground nut −C. arachidicola, C. personata
‘Sigatoka’ leaf-spot disease of banana − C. musae
‘Frog-eye’ leaf-spot of tobacco − C. necotinae
Leaf-spot disease of lady’s finger − C. hibiscus
Leaf-spot disease of cajanus cajan − C. indica
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Leaf-spot disease of cotton− C. gossypina
Leaf-spot disease of rice − C. oryzae.
