Abstract

ISOLATION AND CHARACTERIZATION OF RHIZOSPHERIC BACTERIA IN SOYBEAN (Glycine max (L.) Merrill) CULTIVATED ON FERRALSOLS OF BUONHO TOWN, DAKLAK PROVINCE, VIETNAM

*Prof. Dr. Cao Ngoc Diep, Nguyen Ba Trung and Dr. Van Thi Phuong Nhu

ABSTRACT

Rhizobacterial diversity and population dynamics in the ferralsols rhizosphere of soybean grown in BuonHo town, DakLak province, highland of Vietnam was studied. Soil rhizosphere samples were taken in 24 sites of this region. Physical and chemical characteristics of soil samples and total nitrogen-fixing and phosphate-solubilizing bacteria counts were determined by drop plate count method together with 16S rRNA gene fragments amplified from DNA using eubacterial universal primers (8F and 1492R). A total of 43 isolates were isolated on two media (Burk’s N-free and NBRIP) and all of them have ability of nitrogen fixation and phosphate solubilization together with IAA biosynthesis. Population of rhizobacteria correlated with soil pH and organic matter content in soil closely (P<0.05) and there was relationship between nitrogen-fixing and phosphate-solubilizing bacteria significantly. The sequences from selected rhizobacteria (17 isolates) showed high degrees of similarity to those of the GenBank references strains (between 98% and 99%). From 17 isolates, 10 belonged to Bacilli while Proteobacteria having 1, 1 and 4 were Alpha, Beta and Gamma-Proteobacteria, respectively while there was one was Bacteroides. Based on Pi value (nucleotide diversity), Bacilli group had highest Theta value and Thete values (per sequence) from S of SNP for DNA polymorphism were calculated from each group and Bacilli group had the highest values in comparison to four groups. From these results showed that three strains (Bacillus methylotrophicus BHN5, Bacillus amyloliquefaciens BH8 and Bacillus subtilis BHN16) 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.

Keywords: 16S rRNA, Ferrasols, Gene Sequence, Rhizobacteria, Rhizosphere, Soybean.