Isolation And Characterization Of Bacteria Mitigating Saline-alkine Stress On Zea Mays

Some special microbes presenting in the rhizospheres or inside the plants could enhance plants'tolerance toward saline and alkali environment by microbe-plant interactions.In this study,the natural saline and alkali conditions were simulated?pH9.0,salt concentration 0.45%?,maize were grown under the stress condition in the artificial illumination growth chamber.The following results are showed:1.10 isolates showed stress relieving effect from 850 isolates tested,and strain YM6 is the top performer.In the pot experiment with saline-alkali soil,maize inoculated with YM6 increased the plant height by 37.8%,plant dry weight by 43.9%respectively as compared with the control.The strain YM6 was identified as Bacillus amyloliquefaciens based on the similarity of 16S rRNA sequence.2.The strain YM6 could grow in culture solution with salt concentration of 10%,pH of 11.0,and the maximum growth temperature is 48?.The optimal fermentation medium for strain YM6 was determined by orthogonal test:sucrose 1.50g,glucose7.50g,NH₄NO₃ 2.00g,yeast dip powder 10.00g,CaCl₂ 0.07g,K₂HPO₄ 2.00g,KH₂PO₄ 0.55g,MgSO₄ 0.20g,FeSO₄·7H₂O 0.028 g,ZnSO₄0.003g,niacin 0.01g,pH7.2,distilled water 1L.After fermentation optimization,the growth of YM6 in the optimized culture medium was 50%higher than the TSB medium,and the cost is one third of the TSB medium.3.Salt exerts strong inhibition on maize growth at the concentration of 0.45%,and YM6 could mitigate the salt stress when applied to maize.Compared to the un-inoculated control,plant height increased by 15.2%when YM6 was inoculated to roots of maize seedlings.Root length and plant dry weight of inoculated maize increased by 28.8%and 27.0%respectively.In the hydroponics experiment with pH 9.0,when the maize seedlings inoculated with YM6,the plant height increased 15.2%,root length increased 37.1%and dry weight increased 21.1%respectively as compared with the none inoculated control.We also found that strain YM6 could alleviate alkali stress on maize,improve the rhizosphere micro-environment,and promote the growth of maize seedlings.4.The morphological response of plants to saline-alkali stress is mainly reflected in the above-ground and underground biomass changes.Through metabolomics research,the significantly shifted metabolites are mainly found in the category of steroids,phospholipids,hormones and transmitters,nucleic acids and peptides.Some amino acids such as glutamate and valine were generally considered as stress related metabolites in plants,we found that both glutamate and valine were up-regulated when maize treated with YM6.Another category chemical that confers plants with the stress relief effect is steroids.The steroids substances such as quercetin and rutin were also up-regulated in YM6 treated plants.This study indicated that strain YM6 could effectively alleviate the adverse effects of saline-alkali stress on maize under saline-alkali conditions,and has potential application value for planting maize in saline-alkali soil.