Evaluation of Plant Growth Promoting Rhizobacteria (PGPR) on some grows parameters and photosynthetically pigments of two green bean (Phaseolus vulgaris L.) plant cultivars under salt stress conditions

Nowadays, protection of environment and safe agricultural production are an important aims of the sustainable agriculture. Also, in attention to abundance of saline soil and water resources in the country, the present research was designed to evaluate PGPR inoculation effect on some morphological and physiological traits of two green bean plant cultivars under salinity stress conditions. A greenhouse experiment was designed on factorial arrangement based on completely randomized design with four replications at Sari Agricultural Sciences and Natural Resources University in 2012. The treatments consist of salinity (sodium chloride) in four levels (0, 2.5, 5 and 7.5 dS.m-1), two cultivars (landrace and Hybrid) and pretreatment of PGPR at two levels (non-inoculation and inoculation with Azospirillium brazilence and Azotobacter chroococcum). The results showed that interaction effect of cultivar and bacteria were significant on all physiological parameters, fresh and dry weights and leaf area. Bacteria inoculation increased leaf area with 11 % ratio than non-inoculation treatments. Also, interaction effect of cultivar and salinity were significant in all physiological parameters, shoot fresh weight, leaf fresh and dry weight, leaf area, petiol dry weight and yield except SPAD value. The maximum amount of pod yield with 3.6 gr per plant was observed in hybrid cultivar and 2.5 dS.m-1 salt stress treatment. Interaction effect of bacteria and salinity were significant in all biochemical traits, leaf fresh weight, leaf area, petiol fresh and dry weights and yield. Bacteria inoculation influenced pod yield in all levels. The results exhibited 2.5 dS.m-1 salt stress level and bacteria inoculation treatment with 34% obtained higher amount of pod yield ratio than non-inoculation treatment. In conclusion, results of this research represent the benefit role of PGPR on amelioration of biochemical, morphological parameters and plant growth improvement under mid salt stress conditions