Isolation and characterization of rhizospheric bacteria in rice (oryza sativa l.) cultivated on acid sulphate soils of the Mekong delta, Vietnam

Abstract

Rhizobacteria in the acid sulphate soil rhizosphere of rice grown the Mekong Delta, Vietnam was studied. A total of 160 isolates were isolated on two media (Burk’s N-free and NBRIP) from 80 soil rhizosphere samples were taken in 4 regions (Tu Giac Long Xuyen, Dong Thap Muoi, Trung Song Hau, Ban dao Ca Mau) and all of them have ability of nitrogen fixation and phosphate solubilization. The sequences from selected rhizobacteria (14 isolates) were analysed 16S rRNA gene fragments amplified from DNA using eubacterial universal primers (8F and 1492R) and sequenced. The results showed they had high degrees of similarity to those of the GenBank references strains (between 98% and 99%). From 14 isolates, 8 belonged to Bacilli while Gamma-proteobacteria was 6. There were 18/63 and 22/63 isolates producing IAA and siderophores, respectively. From these results showed that there are two strains as Enterobacter asburiae HG9-3a, Bacillus subtilis HG10-3a and Bacillus subtilis CJL18 revealed promising candidates with multiple beneficial characteristics and they have the potential for application as inoculants adapted to poor soils and local crops because they are not only famous strains but also are safety strains for agricultural sustainable, especially for rice cultivation on acid sulphate soil in the future.