In vitro assessment of superior ACC deaminase containing rhizobial strains and their effect on wheat (Triticum aestivum L.) growth indices

Some strains of Rhizobia known as the most useful soil bacteria are able to produce 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and reduce stress ethylene level in plants. In this research، four strong (R4-Sm، R35-Sm، R71-Sm and R122-Sm)، one mild (R94-Sm)، two weak (R11-Sm and R64-Sm) and two ACCd- (not containing ACC deaminase) strains (R138-Sm and R162-Sm) from Sinirhizobium meliloti were selected for root elongation assay in wheat plant. Experimental treatments were 9 levels of rhizobia and one level as a blank، 2 levels of L-TRP as the precursor of IAA production، 2 levels of Ag as a chemical inhibitor of ethylene action and 2 levels of IAA. The experiment was conducted in completely randomized design in a factorial arrangement with four replications in 24 days، then root length and shoot length were measured. Results showed that ACC deaminase containing rhizobial strains could significantly increase root length in comparison to the blank. Such increase was observed in shoot length as well. Strains R71-Sm and R122-Sm (strong) and R94-Sm (mild) were more effective in improving growth factors of wheat plant.