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The similarity between plant and microbial cells encourage the use of microbial metabolites of halophilic bacteria for the alleviation of salt stress in plants. In the current research work, a compatible solute ectoine extracted from a moderately halophilic bacteria Chromohalobacter salexigens KT989776 was used to enhance flax germination and primary seedling under different levels of salinity. Two successive experiments including germination in Petri plates under six levels of salinity (0, 3, 5, 7, 9 and 11 dS.m-1) and a pot experiment under three irrigating water salinity levels (2, 3 and 4) with two types of ectoine application (spray and soil addition) were conducted. Germination parameters were recorded for the first experiment while a fresh and dry weight of plants and peroxidase activity in addition to sodium-potassium ratio were estimated in the pot experiment. Also, ectoine accumulation in plants was detected using HPLC. Results of LC-MS proved the production of ectoine by C. salexigens KT989776 and ectoine enhanced significantly all germination parameters of flax seeds, decreased sodium accumulation in the plant, increased potassium content, and lowered peroxidase and phenoloxidase activity. Also, HPLC analysis proved that ectoine was detected in all treated samples while not detected in non-treated control.
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