Cercospora & virus

This slide is about the Fungi Cercospora & about viruses

1. CERCOSPORA & VIRUS Presented by, Presented to, Rival June Mawlieh Prof. Priyanka Bagri Saikat Mukherjee Rupak Subhra Sarkar Ranjit Roy

2. CERCOSPORA

3. content Introduction Vegetative structure Conidiophores & Conidia Reproduction in Cercospora Disease caused by Cercospora Symptoms of Cercospora Controlling methods

4. Introduction Cercospora is a genus of Ascomycete fungi Kingdom: Fungi Division: Ascomycota Class: Dothideomycetes Order: Capnodiales Family: Mycospherellaceae Genus: Cercospora , Fresen

5. Vegetative structure The mycelium is well developed, branched, intercellular, septate, slender and brown coloured. In C. arachidicola the mycelium is both external and internal. Intercellular hyphae produced lobed haustoria. Branched haustoria are present in C. personata. In C. arachnida the haustoria are absent.

6. Conidiophores & conidia Conidia are present in only asexual reproductive bodies. Conidia develop on geniculate structures. Conidia are hyaline or pale yellow, obclavate, 38-108µ long and 3-6µ broad. Conidiophores are septate, dark coloured structures coming out in tufts from stomata. Conidiophores are 22-41µ long and 3-5µ broad.

7. Reproduction in cercospora Cercospora reproduces only by means of conidia. A tuft of conidiophores emerge through stomata or ruptured epidermis. Each conidiophores forms single conidium acrogenously at its apex. After the formation of first conidium, the mature conidium is pushed aside due to sub-apical growth of the conidiophores. Each conidium leaves a geniculate scar or conidial scar on the conidiophores at the place of its attachment.

8. Reproduction in cercospora The conidia are disseminated by wind or rain splash. Under suitable conditions 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 Mycospharella arachidicola and M. berkeleyii respectively.

9. Disease caused by cercospora Leaf spot or Tikka disease of ground nut- C. arachidicola, C. personata. Sigatoka leaf spot disease in banana- C. musae. Frog-eye leaf spot of tobacco- C. necotinae. Leaf spot disease of lady's finger- C. hibiscus. Leaf spot disease of rice- C. oryzae.

10. Tikka disease of Ground Nut Leaf-spot disease of Rice ‘Frog-eye’ leaf spot of tobacco

11. Symptoms of cercospora The infections begins as pale green spots on the upper surface of the leaf. These spots gradually enlarge, turn brown in colour. Ultimately entire leaf dries and crumbles down.

12. Controlling methods The first fungicide application should be made at first symptoms. Use recommended rate of fungicides to control it. Avoid using of same fungicide back to back for the same class. Use of high spray pressure (100psi) and high water volume of 15-20 gal/ac.

13. Virus

14. content Introduction Structure of Virus Mechanism of transmission Common Plant Viral Diseases Control of Plant Viral Diseases

15. Introduction A virus is a biological agent that reproduces inside the cells of living hosts. Plant viruses are viruses that infect plants. When infected by a virus, a host cell is forced to produce thousands of identical copies of the original virus at an extraordinary rate. Viruses do not have cells that divide. Viruses contain genes, which give them the ability to mutate and evolve.

16. structure A virion (a virus particle), consists of DNA or RNA, which are surrounded by a protective coat of protein called Capsid. The capsid is made of many smaller, identical protein molecules which are called Capsomers. The arrangement of the capsomers can either be Icosahedral or Helical or more complex. There is an inner shell around the DNA or RNA called Nucleocapsid, formed by proteins. Some viruses are surrounded by a bubble of lipid called Envelope.

17. Mechanism of transmission Plant cells have cell wall, so it is nearly impossible to viruses to breach in order to cause infection. So, plant viruses are typically spread by two common mechanisms: Horizontal Transmission and Vertical Transmission.

18. Mechanism of transmission Horizontal Transmission: The plant virus is transmitted as a result of an external source. To invade the plant, the virus must penetrate the plant's outer protective layer. It also occurs by certain artificial methods of vegetative reproduction employed by horticulturist and farmers. Plant cutting and grafting are common modes by which plant viruses may be transmitted.

19. Mechanism of transmission Vertical Transmission: The virus is inherited from a parent. It occurs in both asexual and sexual reproduction. In asexual methods, the offspring develops from the stems, roots, bulbs etc. of the parent plant, the virus passes along to the developing plant. In sexual reproduction, viral transmission occurs as a result of seed infection.

20. Common plant viral diseases Plant viruses cause various types of plant diseases, such as ring spots, mosaic pattern development, leaf yellowing and distortion, as well as deformed growth. Tobacco mosaic virus- The virus spreads through entry into breaks of cell walls caused by insects or physical damage. (tobacco, potato, tomato, pepper, eggplant) Barley yellow dwarf- It causes discoloration of leaves and the tips of plants, which reduces photosynthesis, shunt growths. (infects several grain and staple crops) Bud blight- It causes stem to bend at the top and the buds to turn brown and drop off the plant. (Soybeans).

21. Bud Blight Tobacco Mosaic Virus Barley Yellow Dwarf

22. Control of plant viral diseases Selection of viral disease free seeds from the diseases free regions. Selection of viral disease free planting material like cutting, bull, rhizomes. Cultivation of trap crops will avoid disease causing insect vector. E.g. Marigold in bhendi for white fly control. Application of Soil Fumigation for nematodes transmitted virus to control nematodes. Application of temperature treatment. Ex. Sugarcane mosaic can be destroyed or reduce by hot water treatment at 52℃ for 30minutes.