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Vegetables Soft Rot Bacteria in the Philippines
Dissertation Abstract:
Five hundred eighteen specimens of vegetable soft rot diseases were collected from 19 towns and 20 cities in 14 provinces in Luzon, 5 in the Visayas and 8 in Mindanao. Of more than 4,00 single bacterial colony inoculations made, 80 isolates (15.6%) of the total specimens collected were found plant pathogenic vegetable soft rotters.
Studies of the morphological, cultural, physiological and biochemical characteristics of the 80 isolates showed that 82.5% were Erwinia carotovora var. carotovora (Jones) Dye; 11.25%, Bacillus subtilis Cohn; 3.75%, Pseudomonas alliicola (Burkh.) Starr and Burkh.; and 1.25%. P. cepacia Burkh. A new species of non-motile xanthomonad, Xanthomonas capsici n. sp., represented the remaining 1.25% of the total isolates.
Erwinia carotova var. carotovora was isolated from cabbage, carrot, celery, Chinese cabbage, cucumber, lettuce, mustard, pechay, pepper, radish and tomato; B. subtilis, from inion, pepper, potato and tomato; P. allicola and P. cepacia, from onion; and X. capsici, from pepper.
Host range studies of the isolates on 13 kinds of vegetables showed that host range of E. carotovora var. carotovora varied from 3 to 13 vegetables and it attacked at least 74% of 7 to 11 vegetables. B. subtilis was pathogenic on Chinese cabbage, cucumber, onion, pepper, radish and tomato, while cabbage, carrot, celery, cucumber, onion, pepper, radish and tomato were also susceptible to P. allicola. X. capsici could infect not only pepper but also onion, potato, and tomato, and only was susceptible to P. cepacia.
The study concluded that in the Philipines, E. carotovora var. carotovora is the most important and widespread bacterial soft rot pathogen of commonly grown vegetables; P. alliicola and P. cepacia are the primary soft rotters of onion; and B. subtilis is an important soft rot pathogen of pepper.