effect of growth promoting rhizobacteria on germination and early growth of two alfalfa cultivars under salinity stress condition

in order to study the effects of seed-bacterial priming (inoculation) on germination and early growth of alfalfa under salinity stress conditions, an experiment was conducted at seed research laboratory and greenhouse of college of agriculture, university of tehran in karaj (iran) in 2011. the experiment was arranged as a factorial in completely randomized design (crd) with three replications. experimental treatments including: three levels of salinity stress (zero (s0), 60 (s1) and 120 (s2) mmol), two levels of alfalfa cultivars (‘bami’ and ‘yazdi’) and 16 levels of bacterial priming (azetobacter, azospirillum, pseudomonas and rhizobium meliloti in single and different double, triple and quadratic integrated forms). the results indicated that applying salinity stress significantly decreased germination and early seedling growth. this descending trend in control (no inoculation) treatment was more than that of treated seeds. application of bacterial priming especially pseudomonas priming and integrated treatments played an important role in moderating the negative effects of salinity on measured traits. according to the results of this study, it seems that plant growth promoting bacteria, by producing and releasing phytohormones such as auxin, gibberellins and cytokinin along with decreasing ethylene level, improve plant growth under salinity stress condition.