Suitable Medium for Increasing Biomass of Antagonistic Streptomyces spp. Against Bacterial Fruit Blotch Disease of Watermelon

บทคัดย่อ

Eight selected Streptomyces isolates namely Streptomyces No.13, 15, 22, 33, 74, 78, 84 and 87, whichwere proved to be effective in controlling bacterial fruit blotch disease in watermelon, were cultured on threetypes of solid media, arginine-glycerol-mineral salt agar (AGMA),yeast extract-malt extract agar (YEME) andglycerol-arginine agar (GAA). It was found that all isolates tested grew rapidly on YEME and AGMA but not onGAA. Subsequently, their effectiveness in inhibiting the growth of Acidovorax avenae subsp. citrulli (Aac), a causalagent of bacterial fruit blotch disease, was tested by bioassay method. The results showed that seven testedisolates of Streptomyces except isolate No.74, which cultured on AGMA and YEME media had a great effect oninhibiting the growth of Aac. The inhibition zones created by 7 isolates were significantly different (p<0.05). Theantibiosis activity against Aac of Streptomyces obtained in agar culture AGMA and YEME showed higher activitythan in GAA. The biomass in liquid culture of four Streptomyces isolates (Streptomyces No.13, 15, 33 and 87) wereevaluated. The highest (p<0.05) dry weights of biomass (ranging from 148.8›289.2 mg/100 ml) of Streptomyces isolate no.13, 15 and 33 were found in AGMB, while Streptomyces isolate No.87 with more rapidly producedbiomass in YEME-broth was 144-376 mg/100 ml.