Citrus canker

PAT 401

1. CITRUS CANKER COLLEGE OF AGRICULTURAL TECHNOLOGY (Affiliated to Tamil Nadu Agricultural University, Coimbatore-3) Kullapuram (Po), ViaVaigai Dam, Theni-625 562 STUDENT Miss. T.DHARANI ID. No. 2015021030 COURSE TEACHER Dr. PARTHASARATHY S Asst. Professor (Plant Pathology)

2. CITRUS CANKER Causal Organism : Xanthomonas axanopodis pv . citri

3. Citrus canker is thought to have originated in the area of Southeast Asia-India. It is now also present in Japan, South and Central Africa, the Middle East, Bangladesh, the Pacific Islands, some countries in South America, and Florida. Some areas of the world have eradicated citrus canker and others have ongoing eradication programs, but the disease remains endemic in most areas where it has appeared because of its rapid spread. DISTRIBUTION

4. SYMPTOMS Characteristic lesions on leaves, stems, and fruit with raised, brown, water-soaked margins, usually with a yellow halo or ring effect around the lesion. Older lesions have a corky appearance, still in many cases retaining the halo effect.

5. Leaf symptom of Canker on both the surface of the leaves Source : citrusalert.html

6. Water soaked lesions on the leaves (Courtesy J. Cubero .)

7. Lesions on woody stem branches and also stem twigs Source : citrusalert.html

8. Symptom on fruit Source : citrusalert.html

9. Twig dieback on stem infection Source : citrusalert.html

10. SYSTEMATIC POSITION KINGDOM : Bacteria PHYLUM : Proteobacteria CLASS : Gammaproteobacteria ORDER : Xanthomonadales FAMILY : Xanthomonadaceae GENUS : Xanthomonas SPECIES : X . axonopodis SUB SPECIES : Xanthomonas axanopodis pv . citri

11. PATHOGEN Rod-shaped , Gram-negative bacterium with polar flagella. The bacterium has a genome length around 5 megabase pairs. A number of types of citrus canker diseases are caused by different pathovars and variants of the bacterium

12. Canker type Name of the strain producing it Places discovered Plants affected Canker A X. axonopodis pv . citri Asia CITRUS Cancrosis B X. axonopodis pv . aurantifolii South America lemons, key lime, bitter orange, and pomelo . Cancrosis C X. axonopodis pv . aurantifolii South America key lime and bitter orange. A* strains only infect key lime. Oman, Saudi Arabia, Iran, and India only infect key lime.

13. Pathogenecity Xanthomonas axonopodis has the capability to form a biofilm for attachment on the host. The biofilm is the result of the production of extracellular polysaccharides ( xanthan ). The biofilm ensures the virulence and epiphytic survival of X. axonopodis pv . citri prior to the development of citrus canker.

14. FAVOURABLE CONDITION Wind-driven rain and splashed rain plays major role in the dispersal of X. axonopodis . The bacteria also favor warm weather. Cankers emerge briskly during fall, slowly during winter and most rapidly in mid to late spring.

15. PRIMARY SPREAD : Infected plant debris. SECONDARY SPREAD : Windblown rain, contaminated equipment and clothing, transport of infected or apparently healthy plants. MODE OF SPREAD

16. SEM of stomata on leaf with Xac bacteria entering stomatalchamber . (Courtesy J. Cubero .) SEM of stomata on grapefruit leaf with Xac bacteria in stomatal chamber. (Courtesy J. Cubero .)

17. Adult moth and larvae of Asian leafminer in feeding gallery. Multiple young citrus canker lesions erupting through leafminer feeding gallery. (Courtesy J. Cubero .)

18. Lemon leaf with thorn scratches infected with Xac . (Courtesy J. Cubero .)

19. Disease cycle of the canker Source : Plant Health Progress Online

20. Disease cycle The bacteria ooze out of the lesions when there is free moisture. During the rainy weather, wind-blown rain carries the inoculum to the new susceptible hosts. The bacteria infect new plants through stomata and wounds or through the natural opening. The infection can form on fruit, foliage and young stem.

21. Leaves and stems are most susceptible to infection within the first six weeks of initial growth. Infection of fruit is most likely to occur during the 90 day period after petal fall during fruit formation. The varied size of lesions on citrus fruit is because of the multiple cycle of infections and can reflect different-aged lesions on the same fruit

22. Management Spray Streptomycin sulphate 500 – 1000 ppm or Phytomycin 2500 ppm Spray COC at 0.2 % at fort night intervals. Spray certain insecticides to control leaf miner. Prune infected twigs before the onset of monsoon.

23. Most of the common species and varieties of citrus are susceptible to canker. Some species are more susceptible than others, while a few species are resistant to infection. Susceptibility Variety Highly susceptible Grapefruit ( Citrus x paradisi ), Key lime ( C. aurantiifolia ), Pointed leaf hystrix ( C. hystrix ), lemon ( C. limon ) Susceptible Limes ( C. latifolia ) including Tahiti lime, Palestine sweet lime; trifoliate orange ( Poncirus trifoliata ); citranges / citrumelos ( P. trifoliata hybrids); tangerines, tangors , tangelos ( C. reticulata hybrids); sweet oranges ( C. sinensis ); bitter oranges ( C. aurantium ) Resistant Citron ( C. medica ), Mandarins ( C. reticulata ) Highly resistant Calamondin ( X. citrofortunella ), kumquat ( Fortunella spp.) Modified from: Gottwald , T.R. et al. (2002). Citrus canker: The pathogen and its impact. Online. Plant Health Progress

24. References Gottwald , T.R, Graham, J.H. and Schubert, J.S. (2002). Citrus canker: The pathogen and its impact. Online. Plant Health Progress doi:10.1094/PHP-2002-0812-01-RV Das, A.K. (January 2003). "Citrus canker - A review"(PDF). Journal of Applied Horticulture. 5 : 52–60.