Isolation And Identification Of Plant Salt-tolerant Microorganisms And Their Effects On Spinach Growth Under Salt Stress

Soil salinity is one of the most serious threats to agriculture causing hampered growth of crops.The study was conducted to isolate,characterize and screen salt tolerant microbes from saline soils of spinach grown areas and their evaluation in improving spinach growth.The sampled soils were moderately to strongly saline,alkaline in nature,low in N and P while adequate in K and Ca concentration.A total of seventeen(17)salt tolerant microbes differing in colony and cell morphology were characterized.All isolated rhizobacteria had capability to biosynthesize phytohormone Indoleacetic Acid(IAA)Fourteen(14)were able to fix atmospheric nitrogen,eleven(11)isolates solubilized inorganic P,ten(10)produced biofilm and fifteen(15)were positive in catalase activity.The isolated rhizobacteria produced IAA in the range of 7.3322.18 mg L-1 and exhibited P-solubilization efficiency up to 70%.The isolated rhizobacteria showed salt tolerance up to 10%Sodium Chloride(NaCl)induced salinity,only six microbes tolerated salt concentration of 12.5%(NaCl)however,none of any rhizobacteria remained viable at 15%(NaCl)amended media plats.The rhizobacterial consortia were tested at various salinity levels for improving spinach growth.The two potential salt tolerant microbes(NIA SP-6&NIA SP-11)were screened on the basis of their performance and found for optimum growth curve and fermentation at pH 7.0 after 48 hrs of incubation period.Both potential microbes were identified as Bacillus firmicutes(NIA SP-06)and Bacillus safensis(NIA SP-11).Both potential strains NIA SP-06 and NIA SP-11 were used as consortia in the net house study.The microbial consortia remained viable(2.01-7.82 log CFU g-1 soil)during spinach growth period.Microbial consortia at medium salinity level(5 dS m-1)showed maximum plant growth(14.83 cm),number of leaves(14.20)fresh weight(2.90 g)and dry weight of leaves(1.290 g).Maximum chlorophyll a and b contents 4.96 and 2.63 mg g-1 FW were recorded in non-inoculated non-saline(0 dS m-1)treatments,however,maximum total chlorophyll content(7.73 mg g-1 FW)were observed at medium(EC 5 dS m-1)salinity conditions.Similarly,inoculated rhizobacterial consortium improved the nutrient Nitrogen,Phosphorus,Potash and Calcium(N,P,K,and Ca)concentrations at medium(EC 5 dS m-1)salinity and non-saline conditions.Na and Cl concentrations were higher at maximum levels of salinity(EC 10 dS m-1)with non-inoculated treatments which affected K+concentrations and spinach growth.Hence,it can be concluded that isolated salt tolerant rhizobacteria have potential for improving spinach growth under medium and slightly saline soil conditions.