Isolation and identification of nitrogen fixing rhizospheric bacteria
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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 (P<0.05). The sequences from selected rhizobacteria (24 isolates) showed
high 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
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