Characteristics of Rhizosphere Bacteria of Sugarcane (Saccharum spp.) Grown on Acrisol and Ferrasol Soils of Dong Nai Province, the Southeast of Vietnam

The study aimed to investigate diversity, population dynamics of nitrogen fixation and phosphate solubilization bacteria in rhizosphere of sugarcane cultivated in acrisol and ferrasol soils of Dong Nai province, the Southeast of Vietnam. Nitrogen total, soluble phosphorus and organic carbon of the soil were determined by using colorimetric method and method described by Walkley-Black. Nitrogen fixation and phosphate solubilization bacteria were isolated on Burk's nitrogen free and NBRIP media. Identification, SNPs and nucleotide diversity of selected bacterial strains were based on 16S rDNA sequences with primers 27F and 1492R, SeqScape@Software and Theta (
) described by Halushka et al.. Validation of nitrogen fixation of strains was carried out by screening presence of nifH with Pol primers. The research found that rhizosphere of sugarcane cultivated in Dong Nai province were slightly acidic, poorly nutrient and had diverse plant growth promoting bacteria. pH, nitrogen total and organic matter component of the soils were three essential factors influencing both populations of nitrogen fixation and phosphate solubilization bacteria in the soils while available phosphorus in the soils was closely related with nitrogen fixation bacteria population rather than phosphate solubilization bacteria population in the soils. Thirty-one strains isolated expressed capacity of fixing nitrogen, solubilizing phosphate and biosynthesizing IAA. Fourteen of thirty-one strains were amplified nifH. Twelve of thirty-one strains with high capacity of plant growth promotion were identified as species of Bacilli, Acidobacteria, Bacteroides and Betaproteobacteria where Bacilli had the highest Pis and thetas. Bacillus megaterium B6 isolated from ferrasols and Sphingomonas sp. P14 isolated from acrisols showed as potential candidates and were proposed to be tested their ability to promote plant growth of sugarcane grown in acrisol and ferrasol soils of Dong Nai province.