ACC deaminase producing plant growth promoting rhizobacteria enhance salinity stress tolerance in Pisum sativum

Salinity stress is one of the most serious environmental stresses which limit plant growth, development and productivity. In this study, we screened 25 bacterial isolates based on the biochemical activity of ACC deaminase. Two potent PGPR namely Bacillus marisflavi (CHR JH 203) and Bacillus cereus (BST YS1_42) having the highest ACC deaminase (ACCD) activity were selected for further analyses such as polymerase chain reaction (PCR), salt tolerance assay, expression analysis, antioxidant assay, etc. The structural gene for ACCD activity was further confirmed by PCR showing the amplicon size ̴ 800 bp. The acdS positive isolates exhibited optimum growth at 3% w/v (NaCl), indicating its ability to survive and thrive in induced saline soil. Inoculation of acdS+ strain on pea plants was found to be efficient and ameliorated the induced NaCl-stress by enhancing the various parameters like plant-biomass, carbohydrates, reducing sugars, protein, chlorophylls, phenol, flavonoids content and increasing antioxidants enzymes levels in plants. Moreover, the expression of ROS scavenging genes (PsSOD, PsCAT, PsPOX, PsNOS, PsAPX, PsChla/bBP), defense genes and cell rescue genes (PsPRP, PsMAPK, PsFDH) were analyzed. Inoculated plants exhibited a higher gene expression level and salt tolerance under 1%NaCl concentration. Thus, our results indicate that CHR JH 203 and BST YS1_42 strain showed the highest plant growth-promoting attributes could be used as bio-inoculants for crops under saline stress in the field towards sustainable crop development.