Salt-tolerant and plant growth-promoting bacteria isolated from high-yield paddy soil

The growth and productivity of rice is negatively affected by soil salinity. However, some salt-tolerant bacteria can improve plant health under saline stress. Here, 305 strains were isolated from paddy soils in Taoyuan, China. Among these, 162 strains were tested for salt-tolerance, and 67.3%, 28.4%, and 9.3% of the strains could grow in media with NaCl concentrations of 50, 100, and 150 g/L, respectively. Phylogenetic analysis of 74 of these 162 strains indicated that these bacteria belonged to the Bacillales (72%), Actinomycetales (22%), Rhizobiales (1%), and Oceanospirillales (4%). Thirty of the salt-tolerant strains were screened for plant growth-promoting activities under axenic conditions at 3, 6, 9 and 12 g/L NaCl. Of these strains, 43%-97% improved rice germination energy or capacity, while 63%-87% had increased shoot and root lengths. Among the growth promoting strains, TY0307 was the most effective at promoting rice growth, even at high salt concentrations. The promotive effects of this strain were associated with its production of 1-aminocyclopropane-1-carboxycarboxylate deaminase, IAA, and siderophores, the induction of proline accumulation, and the reduction of salt-induced malondialdehyde content. These results suggest that several strains isolated from paddy soil could improve rice salt tolerance and may be targets for the development as biofertilizers.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author