Effectiveness of some native Rhizobium spp. containing ACC-deaminase in amelioration of negative effects of stress ethylene on growth parameters in Oilseed rape (Brassica napus L.)

In this study، the ability of 32 rhizobium strains (26 strain of Sinorhizobium meliloti (SM))، 4 strains of Rhizobium leguminosarum biovar phaseoli (Rlp) and 2 salt tolerance strains of Rhizobium leguminosarum biovar viciae (Rlv) for use of ACC as individual nitrogen source in RMM media was evaluated. Based on the results، 25 strains were found positive for ACC-deaminse، and strains according to growth in the RMM media containing ACC were categorized into three groups of strong، medium، and weak. In the next step، in 2011 a series of greenhouse experiments were conducted for investigating the effectiveness of two strains from strong group (R281Rlp and R103Sm) and one strain from weak group (R29Sm) with control treatment، for the promotion of growth parameters of canola under the salinity levels of 0، 3، 6، and 9 ds/m in factorial format experiment as randomized complete block design with three replications. The Results showed that R281Rlp inoculation، even at higher salinity (9dS/m)، significantly increased wet and dry weight of root (32 and 62. 6%، respectively)، wet and dry weight of shoot (22 and 23. 5%، respectively)، height (49%) and nitrogen uptake (50%) compared to control treatment. Furthermore، at this level of salinity، R103Sm inoculation increased the uptake of Phosphorous up to 34. 5% compared to control. A positive correlation was observed between ACC-deaminase activity of bacterial isolates and plant growth parameters; especially root biomass، (Pearson correlation coefficients > 0. 82). These results revealed that the strains containing high ACC-deaminase activity were more successful in improving the growth parameters of canola seedling، which confirms that using of these strains may be suggested as a biologic alternative to the amelioration of increasingly saline stress.