Sangeeta PaulBANDEPPA2016-11-252016-11-252011http://krishikosh.egranth.ac.in/handle/1/87492T-8487Salinization of soil is a serious problem and is increasing steadily in many parts of the world. Soil salinity affects the germination, establishment, growth and development of plants leading to huge losses in productivity. Maize, one of the major cereal crops in India, is a moderately salt sensitive plant. Yield reduction of more than 50% has been observed due to exposure of the plant to moderate salt stress. Beneficial microorganisms colonizing plant rhizosphere can influence plant growth and development. Salinity affects their survival, growth and plant growth promoting activities. Salt tolerant plant growth promoting bacteria can be harnessed for their beneficial properties in such environments in which other microorganisms hardly survive. In the present investigation, salt tolerant bacteria were characterized and evaluated for alleviation of salt stress in maize. Fifteen bacterial isolates were screened for salt tolerance. Based on their high salt tolerance, two cultures SSA61 and SSM66 were selected for further studies. Effect of different concentrations of NaCl on their growth was determined. Both the cultures were able to grow up to 15% NaCl concentration. The isolates were also characterized for their plant growth promoting activities like P solubilization, IAA production, ARA, siderophore and HCN production, ACC deaminase activity, etc. in the presence as well as absence of salt. Siderophore production was not observed in any of the isolates. With increase in NaCl concentration an increase in all the plant growth promoting activities was observed. However, 15% NaCl concentration had a slightly inhibitory effect on IAA production, ARA, siderophore and HCN production by the selected isolates. The isolates also improved seed germination of wheat in presence of salt. The isolates were identified as Bacillus sp. and Stenotrophomonas sp. by 16S rDNA sequencing. A pot culture experiment was carried out under saline soil and normal soil conditions to evaluate the effect of these cultures on maize growth. Various plant physiological parameters viz. amino acid, proline, starch, sugars, phenolics and chlorophyll, content, membrane stability index, membrane injury index, relative water content were also studied. Plant phosphorus, nitrogen, sodium and potassium contents were also determined. There was a decrease in membrane injury index while all other parameters studied were significantly enhanced due to inoculation with these cultures under salt stress. Thus, salt tolerant bacteria possessing plant growth promoting activities can be harnessed for salt stress alleviation in crops and to improve plant growth under salinity stress.Thesis