CITRUS CANKER K R.pptx

CITRUS CANKER K R.pptx

1. Plant diseases CITRUS CANKER K R MICRO NOTES 1

2. CITRUS CANKER Citrus canker is a plant disease caused by bacterium Xanthomonas citri (synonyms: Xanthomonas axonopodis pv. citri/ Xanthomonas campestris pv. citri). All types of citrus are affected by the disease. It can be a serious disease where rainfall and warm temperatures are frequent. There are many types of citrus canker such as citrus canker A,B,C,D,E. It is mostly a leaf spotting and fruit rind blemishing disease. A fruit infected with it is safe to eat but too unsightly to be sold. Highly susceptible citrus species are grapefruit, lime and lemon whereas highly resistant ones are citron, mandarins. K R MICRO NOTES 2

3. A B C D E A: Grapefruit B: Lime C: Lemon D: Citron E: Mandarin K R MICRO NOTES 3

4. Causal organism The bacterium causing citrus canker was known as Xanthomonas campestris pv. citri (Hasse). Although, Gabriel, et al., (1989) proposed reinstatement of the name Xanthomonas citri . Finally Vauterin, et al., gave the term Xanthomonas axonopodis pv. citri. There are aerobic, rod shaped, Gram negative bacteria which posses capsules but not spores. The cells measure 0.5-0.75 х 1.5-2.0 μ m and it contains a single polar flagellum. Canker A is caused by Xanthomonas citri (In Asia), cancrosis B is caused by X. axonopodis pv. aurantifolii (In South America, Mexico). Cancrosis C is caused by X. axonopodis pv. aurantifolii was isolated from Mexican lime in Brazil. Other forms of canker have in reported but their existence still remains controversial. K R MICRO NOTES 4

5. X. citri Light microscopic view of X. citri Xanthomonas grown under laboratory conditions K R MICRO NOTES 5

6. symptomatology The disease occurs on leaves, twigs, thorns, older branches and fruits as brown spots with rough surface. Leaf lesions first appear as small, round, watery, translucent spots. They are raised and become yellowish brown. Initially it develops on the lower surface of leaf and then on both sides, as the disease advances the surface of spot becomes white or greyish and finally ruptures. In case of severe infection, defoliation of leaves may happen, plants become stunted and yield is reduced. The lesions when dispersed by windblown rain can spread to other plants in the area. K R MICRO NOTES 6

7. The bacteria can enter through a plant’s stomata or through wounds on leaves or other green parts. Symptoms may appear after several months of infection, lower temperature increases the latency of the disease. Citrus canker bacteria can stay viable in old lesions and other plant surfaces for several months. K R MICRO NOTES 7

8. Lesions on the twigs, leaves, thorns, fruits K R MICRO NOTES 8

9. Etiology Fawcett and Jenkins found lesions of citrus on Kew specimens of Citrus medica collected in Dehradun in 1827 and 1831. The disease might have originated in India or Java and spread to other countries. The disease was first recorded in Japan. Now it is known to occur in practically every citrus growing area of the world. The disease is of worldwide importance and many millions of dollars have been spent in eradication campaigns in addition to direct disease loses. The disease was once reported to have been eradicate Australia, new Zealand, South Africa and the United States, its reappearance was reported during the 1980s. K R MICRO NOTES 9

10. In USA, it was recognised as a new disease in 1913, it became so severe to mass eradicate diseased trees and nursery stock. It was claimed that it was completely eradicated from USA in 1933. However it was reappeared in 1986 and again same eradication measure was taken. The disease was declared eradicated by 1994 and again it re-emerged in the same area in 1997. There is no complete cure for citrus canker disease. K R MICRO NOTES 10

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12. Disease management Control measures include quarantine, use of canker free nursery stock, sanitary precautions. The growth of resistant varieties. Burn diseased plants. Spray one percent Bordeaux mixture. Prune affected plant parts, collect and burn. Control leaf miners. Rangaswamy et al., (1959) have shown that the disease can be controlled under field conditions with a spray of antibiotics such as streptomycin at 500 -1000 ppm at regular intervals of 15 days. K R MICRO NOTES 12

13. reference Plant Diseases ninth edition - R.S. Singh Plant Diseases - Gyan Deep Singh Plant Diseases, the yearbook of agriculture 1953 Plant Pathology - John Charles Walker Diseases of Crop Plants in India - G. Rangaswami - A. Mahadevan Agricultural Microbiology - G. Rangaswami - D.J. Bagyaraj Plant Pathology - R.S. Mehrotra - Ashok Aggarwal Fundamentals of plant pathology by V.N. Pathak, N.k. Khatri, M. Pathak K R MICRO NOTES 13

14. Thank you K R MICRO NOTES 14