Abstract

ISOLATION AND CHARACTERIZATION OF ENDOPHYTIC AND RHIZOPHERIC BACTERIA ASSOCIATED SWEET-POTATO PLANTS CULTIVATED ON SOILS OF THE MEKONG DELTA, VIETNAM

Ly Ngoc Thanh Xuan*, Dr. Tran Van Dung, Prof. Dr. Ngo Ngoc Hung,
Prof. Dr. Cao Ngoc Diep

ABSTRACT

Rhizobacteria and endophytic bacteria in the acid sulphate rhizosphere soils and stems/roots of sweet potatoes grown on acid-sulphate soils of the Mekong Delta, Vietnam were studied. A total of 96 isolates were isolated on two media (Burk’s N-free and NBRIP) and 260 endophytic isolates (128 isolates from LGI medium and 132 isolates from Nfb medium) from 60 rhizosphere soil samples were taken in three regions (Tu Giac Long Xuyen, Dong Thap Muoi, Trung Song Hau) and all of them have ability of nitrogen fixation and phosphate solubilization. The sequences from selected rhizobacteria and endophytic bacterial isolates (12 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 12 isolates, 3 belonged to Bacilli while Beta-proteobacteria and Gamma-proteobacteria were 3 and 6 strains, respectively. From these results showed that there are six strains as Pseudomonas taiwanensis LA1-3-3, Bacillus circulans KG2-3-2, Klebsiella sp. HG5-3-2, Enterobacter asburiae KG9-2-1-1, Burkholderia metallica HG7-2-1-2, Enterobacter cloacae AG1-1-1-1 revealed promising candidates with multiple beneficial characteristics and they have the potential application as inoculants adapted to poor soils (unfertile soils) and local crops because they are not only famous but also safe strains for sustainable agriculture, especially for growing sweet potatoes on acid sulphate soils in the future.

Keywords: 16S rRNA, Acid sulphate soil, Gene Sequence, Endophytes, Mekong Delta, Rhizobacteria, Rhizosphere, Sweet potato.