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Black rot, caused by the bacterium ''Xanthomonas campestris'' pv. campestris (Xcc), is considered the most important and most destructive disease of crucifers, infecting all cultivated varieties of brassicas worldwide.〔Alvarez AM. "Black rot of crucifers." In: Slusarenko AJ, Fraser RSS, van Loon LC (Eds.) ''Mechanisms of Resistance to Plant Diseases.'' Dordrecht, The Netherlands: Kluwer Academic Publishers, 2000. pp 21-52.〕〔Williams PH. "Black rot: a continuing threat to world crucifers." ''Plant Disease'' 64.8 (1980): 736-742.〕 This disease was first described by botanist and entomologist Harrison Garman in Lexington, Kentucky, USA in 1889.〔Garman H. "A bacterial disease of cabbage." ''Kentucky Agric Exp Stat Rep'' 3 (1890):43-46.〕 Since then, it has been found in nearly every country in which vegetable brassicas are commercially cultivated.〔Chupp C. “Black rot of cabbage.” ''Manual of Vegetable Plant Diseases.'' New Delhi, India : Discovery Publishing House, 2006. p. 132-133.〕 Host infection by Xcc can occur at any stage of the plant life cycle. Characteristic symptoms of black rot caused by Xcc are V-shaped chlorotic to necrotic lesions extending from the leaf margins and blackening of vascular tissues. The pathogen thrives in warm and humid climates and is rapidly disseminated in the field. Use of clean seed, crop rotation, and other cultural practices are the primary means of control of black rot. However, in developing countries such as those in South and Eastern Africa, black rot remains the greatest impediment to cabbage cultivation due to unreliable "clean" seed, multiple croppings annually, and high susceptibility of popular local cultivars to the disease.〔Massomo SMS, Mabagala RB, Swai IS, Hockenhull J, Mortensen CN . “Evaluation of varietal resistance in cabbage against the black rot pathogen, ''Xanthomonas campestris'' pv. campestris in Tanzania.” ''Crop Protection'' 23,4(2004): 315-325.〕 ==Hosts and symptoms== Members of the plant family Brassicaceae (Cruciferae), which includes cabbage, broccoli, cauliflower, kale, turnip, oilseed rape, mustard, radish, and the model organism ''Arabidopsis thaliana'' are affected by black rot.〔〔("Black rot of cabbage and other crucifers." ) Integrated Pest Management. University of Illinois Extension. Dec 1999.〕〔Miller SA, Sahin F, and Rowe RC. ("Black rot of crucifers." ) Extension fact sheet HYG-3125-96. Ohio State University Extension. 1996.〕〔Seebold K, Bachi P, and Beale J. ("Black rot of crucifers ." ) UK Cooperative Extension Service . University of Kentucky. Feb 2008.〕〔 Host infection by Xcc causes V-shaped chlorotic to necrotic foliar lesions, vascular blackening, wilting, stunted growth, and stem rot symptoms.〔 As the pathogen proceeds from the leaf margins towards the veins, water stress and chlorotic symptoms develop due to occlusion of water-conducting vessels by bacterial exopolysaccharides and components of degraded plant cell walls.〔〔 The darkening of vascular tissues following bacterial invasion gives the black rot disease its name.〔 Lesions produced by Xcc may serve as portals of entry for other soft-rot pathogens such as ''Pectobacterium carotovorum'' (formerly ''Erwinia'' ''carotovora'') and ''Pseudomonas marginalis''.〔〔〔 These symptoms may be confused with fusarium wilt of cabbage (fusarium yellows), caused by the fungus ''Fusarium oxysporum'' f. sp. ''conglutinans''. In contrast to black rot, in which the pathogen invades leaf margins and causes chlorotic to necrotic symptoms that progress downwards in the plant, fusarium wilt symptoms first develop in the lower portions of the plant and move upwards.〔Sherf, A. ("Fusarium yellows of cabbage and related crops." ) New York State Cooperative Extension. Cornell University. Jan 1979.〕 Furthermore, leaf veins invaded by Xcc turn black compared to the dark brown vein discoloration found in fusarium wilt.〔Sherf, A. ("Fusarium yellows of cabbage and related crops." ) New York State Cooperative Extension. Cornell University. Jan 1979.〕〔"Black rot of cabbage and other crucifers." Integrated Pest Management. University of Illinois Extension. Dec 1999.〕 Symptoms of black rot may vary widely among different species of crucifers. On cauliflower, Xcc infection via stomates causes black or brown specks, scratched leaf margins, black veins, and discolored curds.〔Miller SA, Sahin F, and Rowe RC. "Black rot of crucifers." Extension fact sheet HYG-3125-96. Ohio State University Extension. 1996.〕 Additionally, the severity of symptoms and aggressiveness of the disease varies between different strains of the Xcc pathogen.〔 The isolates can be differentiated into races based on the reaction of several Brassica lines after inoculation. A race structure including 5 races (0 to 4) was first proposed in 1992;〔Kamoun S, Kamdar HV, Tola E, Kado CI. “Incompatible interactions between crucifers and ''Xanthomonas campestris'' involve a vascular hypersensitive response: Role of the ''hrpX'' locus.” ''Molecular Plant-Microbe Interactions'' 5 (1992): 22-33.〕 a revised classification model with 6 races was proposed in 2001〔Vicente JG, Conway J, Roberts SJ, Taylor JD. “Identification and origin of ''Xanthomonas campestris'' pv. ''campestris'' races and related pathovars.” ''Phytopathology'' 91 (2001): 492-499.〕 and, more recently, the model was expanded to include nine races.〔Jensen BD, Vicente JG, Manandhar HK, Roberts SJ. “Occurrence and diversity of ''Xanthomonas campestris'' pv. ''campestris'' in vegetable brassica fields in Nepal.” ''Plant Disease'' 94 (2010): 298-305.〕〔Fargier E, Manceau C. “Pathogenicity assays restrict the species ''Xanthomonas campestris'' into three pathovars and reveal nine races within ''X. campestris'' pv. ''campestris''.” ''Plant Pathology'' 56 (2007): 805-818.〕 :::: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Xanthomonas campestris pv. campestris」の詳細全文を読む スポンサード リンク
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