Citrus Canker.pptx

Citrus canker is a bacterial disease caused by the bacterium Xanthomonas citri, producing lesions and cankers on citrus plants.
Cankers are open wounds or dead tissue surrounded by living tissues.
The disease was first reported in Japan in 1904.
It is a serious disease and is worldwide in distribution.
It is particularly serious in India, China, Japan and Java.
In 1915, Hesse first established the bacterial nature of the disease and described the organism as Pseudomonas citri.
Breed et al (1948) included it under Xanthomonas citri.
The Material is Useful for School and Undergraduate students.

1. K.GAYATHRI 18ZOO07 S.HARINI 18ZOO09 PRSENTED BY PLANT PATHOLOGY Part I Citrus Canker E.M.G. YADAVA WOMEN’S COLLEGE, MADURAI-14 (An Autonomous Institution –Affiliated to Madurai Kamaraj University) Re- Accredited (3rd Cycle) With Grade A+ And CGPA 3.51 By NAAC Dr. V.Vijaya Assistant Professor of Botany E.M.G. Yadava Women’s College Madurai, Tamil Nadu

2. Citrus Canker Citrus canker is a bacterial disease caused by the bacterium xanthomonas citri , which produces lesions and cankers on citrus plants. Cankers are open wounds or dead tissue surrounded by living tissues . The disease was first reported in Japan in 1904 . It is a serious disease and worldwide in distribution . It is particularly serious in India, China, Japan and Java. In 1915, Hesse first established the bacterial nature of the disease and described the organism as Pseudomonas citri . Breed et al (1948) included it under Xanthomonas citri .

3. Causal Organism (or) Pathogen Class : Schizomycetes Order : Pseudomonadales Family : Pseudomonadaceae The pathogen responsible for citrus canker is a bacterium called Xanthomonas citri ( Pseudomonas citri ). Xanthomonas citri is a Gram-negative, aerobic bacterium . It has a single polar flagellum ( monotrichous ). It is a capsulated bacillus and non-spore forming bacterium . The colonies are yellow in colour .

4. Symptoms Citrus canker attacks all plant parts above ground level i.e., leaves, twigs and fruits. The disease first appears as a small yellow spot on young leaves . These yellow spots are called lesions . These lesions first appear on the lower surface of the leaves . The lesions becomes raised and turn brown in color . In the advanced stages of infection , the lesions rupture in the centre, gives a rough corky and crater-like appearance. The yellow spots are also formed on the twigs . On the older twigs they are prominent and irregular in shape. The spots increase in size and coalesce to form elongated lesions .

5. The bacterium also produces yellow spots in fruits . The canker on the fruit is only a lesion of the rind (skin). It does not penetrate into the flesh of the fruit . The market value of the fruit is lowered due to the presence of brown colored outgrowth on them. Canker on A) Leaves and B) Fruits

6. Etiology and Dissemination The bacterium enters the host plant either through natural openings ( stomata ) or through wounds. The diseased twigs and leaves are the main sources of the inoculum. On penetration into the host, the bacterium multiplies in the intercellular spaces . It dissolves the middle lamella and establishes in the cortex and forms cankerous outgrowths. The exudate released from these outgrowths contains numerous bacteria . The bacteria are disseminated by wind, rain and insects especially leaf-mites. Man also plays a major role in its dissemination through infected nursery stock . The climatic factors which favors the disease are the mild temperature and wet weather.

7. The infection is most severe, when the temperature is 20-35°C . The pathogen can survive up to six months in the infected leaves. It remains viable up to 52 days in the sterilized soil, but in the unsterilized soil viability is only for 9-17 days. Various Control or Prevention methods are adopted for the regulation of citrus canker disease. Some important control measures are as follows: The infected trees must be removed and burnt. Pruning of diseased twigs and leaves during dry season is practiced.

8. Disease free nursery stock should be planted. Disease resistant varieties should be cultivated. Spraying of neem cake at the rate of about 7kg per acre , is found to be effective in controlling the disease. Spraying the plant with 1% Bordeaux mixture or copper oxychloride 0.25% before planting. Rangaswami et al. (1959) have shown that the disease can be controlled with a spray of antibiotics like streptomycin (500-1000 ppm) or phytomycin (2500 ppm) at 15 days intervals. Quarantine regulations, prohibiting movement of diseased stock to disease free-areas will help in checking the spread of the disease to new areas.

9. Reference: PB. Annie Ragland, V Kumaresan 2002 , Fungi And Plant Pathology, Publisher‏, Saras Publication- Tamil Nādu Google Images

10. THANK YOU