Chiang Mai Journal of Science

Acidotolerant neutrophilic actinomycetes are suitable as agent for plant growth promotion due to their biological activities and survival under acidic conditions. In this study, 75 actinomycetes isolated from Kantulee peat swamp forest were screened for siderophore production, phosphate solubilization and in vitro antagonism against phytopathogens. Results showed that siderophore production at pH 5.0 and pH 7.0, phosphate solubilization, and antagonistic activities against Fusarium moniliforme, Helminthosporium oryzae and Rhizoctonia solani occurred at 84%, 60%, 55%, 17%, 76%, and 36% of the isolates, respectively. Seventeen isolates that exhibited growth at pH 5.0 and pH 7.0, with broad plant growth promoting activities were selected for in vitro rice seed germination test. Subsequently, four strains, Amycolatopsis acididurans K13G38T, Nocardia sp. K12M13, Streptomyces sp. K92M3 and Streptomyces sp. K93G4 identified by 16S rRNA gene sequence analysis, were tested for their activities to promote rice seedlings under pot experiments. Seeds primed with strain K13G38T showed the highest vigour index under pot experiments. This study demonstrated that actinomycetes isolated from peat swamp forest could potentially be developed as beneficial rice seed biopriming agents.