Optimum Conditions for Indole-3-Acetic Acid Production by Streptomyces and its Stimulation on Seed Germination of Rice cv. KDML105
This study was to investigate the effects of temperature, pH and NaCl on indole-3-acetic acid produced by 4 bacterial species isolated from vermicompost, that were Streptomyces sp. SEF4, Streptomyces sp. SEF11, Streptomyces sp. SEF28 and Streptomyces sp. SEF37. Effect of the culture filtrate from four strains of Streptomyces on germination stimulated and seedling growth of rice cultivar KDML105 were also determined. The results showed that the optimum of indole-3-acetice acid produced by four strains of Streptomyces were observed at 27-30ºC (18.8-20.7 mg/l) and pH 7-9. Streptomyces sp. SEF4, Streptomyces sp. SEF11, Streptomyces sp. SEF28 could produce indole-3-acetic acid in the presence of 2.55% NaCl. However, using suspension of these bacterial isolates could not stimulate seed germination and seedling growth of rice cultivar KDML105. The culture filtrate of Streptomyces sp. SEF11, Streptomyces sp. SEF28 and Streptomyces sp. SEF37 trended to stimulate germination of seed while culture filtrate of Streptomyces sp. The SEF4 and Streptomyces sp. SEF11 trended to increase shoot length but culture filtrate of all strains decreased the root length. Thus, these Streptomyces strains could produce indole-3-acetic acid under alkaline conditions and salt stress conditions which could be applied to use with rice cultivation in the North eastern of Thailand in the future.