Effects of plant growth promoting rhizobacteria (PGRP) on germination and seedling growth of wheat (Triticum estivum L.) under salt stress

In order to investigate the effects of plant growth promoting rhizobacteria (PGRP) on germination and seedling growth of wheat (Triticum estivum L.) under salt stress an experiment was conducted in the physiology laboratory of Sari Agricultural Sciences and Natural Resources University. The experiment was a factorial on the basis of a completely randomized design with three replications. Shanghai cultivar was inoculated with growth promoting rhizobacteria (including Azotobacter coroocoocum، Azospirillum brasilens، Pseudomonas putida، Bacillus lentus) separately، or using different combinations، when subjected to salt stress (including 0،3 and 6 dS. m-1). Results indicated that different rhizobacteria and different salt stresses had significant effects on all measured traits except for shoot to root ratio. Meanwhile، interaction effects of two treatments caused significant differences except for germination rate and percentage and seedling vigor index. Inoculation of Azotobacter sp. and Azosprillium sp. separately and in combination with the other rhizobactria strains increased germination rate of wheat، compared to the control treatment. Combination of Azotobacter sp. and Azospirillum sp.، combination of Azospirillum، sp. Pseudomonas sp. and Bacillus sp. and all rhizobactria significantly improved seedling vigor index. The root and shoot length of wheat was affected by salt stress and decreased with increasing salt stress. However، root length in Azospirillum sp. and Azotobacter sp. together and all rhizobacteria combination were similar to the control treatment. Salt stress at 6 dS. m-1 significantly decreased shoot dry weight. However، this was not the case for the 3 and 6 ds. cm-1 treatments for double inoculation of Azospirillum sp. and Azotobacter sp.