Efficacy of Auxin-producing Bacillus Strains on Vegetative Traits and Relative Expression of ARF15 Gene in Two Genotypes of Chickpea Under Salinity Stress

Soil salinity is one of the most crucial agricultural problems that in addition to having negative effects on crop production, causes hormonal imbalance and growth reduction in the plant. Plant growth-promoting rhizobacteria (PGPR) are a range of bacterial strains from different groups that live in plant roots and rhizospheres and can cause the plants to withstand stress by causing complex alterations in their growth and development. PGPR alters plant metabolism, signaling, and hormone homeostasis. The present study aimed to evaluate the effect of two auxin-producing Bacillus strains on vegetative traits and the relative expression of the ARF15 gene of two genotypes of chickpea (Cicer arietinum) (MCC77 and MCC68) under salinity stress of 50 and 100 mM sodium chloride in greenhouse conditions. The number of sub-branches of MCC68 has been significantly increased in the inoculation of strains at the concentrations of 0.5 and 1 in the presence of 50 mM sodium chloride. Moreover, the inoculation of Bacillus amyloliquefaciens (FZB42) and Bacillus. cereus at a concentration of 0.5 and 1 led to a significant increase in the fresh weight of MCC77 root. In addition, FZB42 at the concentration of 1 caused a significant increase (28.20%) in the height of MCC77 plants in the presence of 100 mM sodium chloride. In the inoculation of Bacillus sp. at the concentration of 0.5 and the presence of 50 mM sodium chloride, the relative expression of the ARF15 gene of MCC68 genotype showed a 9-fold increase. Both FZB42 and B. cereus strains affected the vegetative traits of MCC68 and MCC77 genotypes, which indicated the role of PGPR in increasing the supply of enzymatic and non-enzymatic metabolites, and the expression of plant genes in response to abiotic stresses.