In recent years, numerous studies have been done on using biological approaches instead of chemical fertilizers and increasing sustainable production in agriculture systems. Some microorganisms can promote growth and yield in the plant. In this study, the effect of several plant-growth-promoting bacterial strains were evaluated on germination and seedling growth of four different plant species including sesame (Sasamum indicum), canola (Brassica napus), wheat (Triticum turgidum L.) and barley (Hordeum vulgar L.).

The seeds of four plant species were inoculated by five bacterial strains including Bacillus subtilis, Bacillus pumilus, Azotobacter chroococcum, Rhizobium meliloti and Stenotrophomonas. Their effects were evaluated on seed germination and growth parameters of seedlings under in vitro condition.

The results of this experiment showed that among gram-negative bacteria, the Stenotrophomonas sp. enhanced seed germination, root number, root length (cm), shoot length (cm), root fresh weight (g) and shoot fresh weight (g) significantly. Among the gram-positive strains, Basillus subtilis mostly promoted germination and the seedling growth. Discussion and

The effects of B. Pumilus on germination and seedling growth of cereals was evaluated first. The results indicated the potential application of Stenotrophomonas sp. on enhancement of plant seed germination, but the positive effects of it on oil seed crops was less than cereals seed. B. pumilus showed the most negative effect on germination of barely and canola.