Isolation and identification of rhizospheric bacteria in Acrisols of maize (Zea mays L.) in the eastern of South Vietnam

Abstract

Rhizobacterial diversity and population dynamics in the Acrisol rhizosphere of maize grown in the eastern of South Vietnam was studied. Soil rhizosphere samples were taken in three provinces 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 149 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 (Phigh degrees of similarity to those of the GenBank references strains (between 97% and 99%). From 24 isolates,13 belonged to Beta-Proteobacteria, while 11 were Firimicutes and Actinobacteria. Based on Pi value (nucleotide diversity), rhizobacteria (PGPR) group in Tay Ninh province had higher than rhizobacteria (PGPR) group in Baria-Vungtau province with the highest Theta value (per site). From these results showed that three strains (Burkholderia vietnamiensis VDN6a, VDB6a and VDN7c) 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.