Forty-one isolates of Acidovorax avenae subsp. citrulli were characterized based on physiological and biochemical aspects. All isolates induced typical symptoms of fruit blotch on seedlings, plants and fruits of melon (Cucumis melo) and watermelon (Citrullus lanatus). The Scott-Knott test (P = 0.05) separated the isolates for disease index in 5 and 7 groups, respectively, for melon and watermelon seedlings, and 2 groups for plants of these two hosts. In fruits, all isolates were separated in 3 and 10 groups for the variable diameter of extern lesion, and 2 and 9 groups for lesion depth, respectively, for melon and watermelon. All isolates induced hypersensitivity in tobacco (Nicotiana tabacum); utilized the composites asparagine, L-leucine and DL-acid lactic; produced enzymes lipolytic and phytohormone indoleacetic acid. None of the isolates studied showed pectinolytic, amylolytic, cellulolytic or proteolytic activity, nor produced polysaccharide levan and toxin syringomycin; showed sensitivity to copper oxychloride (120 µg mL-1), cuprous oxide (120 µg mL-1), copper hydroxide (138.2 µg mL-1), streptomycin sulfate (25 µg mL-1) and Agrimaicin 500 (428 µg mL-1); and resistance to kasugamycin (87 µg mL-1), agrimicin (200 µg mL-1), erythromycin (15 µg), gentamicin (10 µg), amoxicilin (10 µg), neomycin (30 µg) streptomycin (10 µg), norfloxacin (10 µg) and rifampicin (5 µg). With regard to tetracycline (30 µg), variability was found among the 41 isolates, with 41.5% considered resistant, 46.3% moderately sensitive and 12.2% highly sensitive.
fruit-blotch; Cucumis melo; Citrullus lanatus; physiological and biochemical characteristics
