Fruit blotch of watermelon [Citrullus lanatus (Thumb.)] in Northeastern Thailand: etiology and factors affecting disease development
1996
Srichumpa-Pinyapong, P. | Natural, M.P. (Philippines Univ. Los Banos, College, Laguna (Philippines))
Thirty strains of the fruit blotch bacterium were isolated from three watermelon areas of Northeastern Thailand. All isolates were Gram negative, non-spore farming rods, about 0.9 x 1.8 micron, having a single polar flagellum. These colonies were creamy and translucent, about 1 mm in diameter after 2-3 days in nutrient agar. The colonies were convex, circular and entire. No flourescent pigment was produced in KB medium. Other morphological, physiological and biochemical properties suggest that the causal bacterium was Acidovorax avenae subsp. citrulli (syn. Pseudomonas pseudoalcaligines subsp. citrulli Schaad et al., 1978). Seed transmission was not observed from the limited number of seed collected from naturally infected plants. However, watermelon seedlings of 10 hybrids with seeds soaked in bacterial suspension before planting developed symptoms one week after. Disease incidence ranged from 0.83 percent. Factors that affected development of fruit blotch in watermelon fruits were inoculum concentrations, age of fruits, wounds and variety
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