Evaluation of ACC Deaminase producing bacteria over non-producers in protecting Vigna radiata growth under Salt and Boron stress

The 1-aminocyclopropane-1-carboxylate deaminase (ACCD) is a crucial bacterial trait found in rhizobacteria for amelioration of different plant stresses. A co-inoculation approach is explored in this study. Our objective was to compare the efficacy of PGPB with ACCD activity and without ACCD activity in improving the growth of legume Vigna radiata under salt and boron stress. Two isolates were selected for comparative study in the mitigation of salt and boron stress with and without ACCD activity. Seeds of Vigna radiata were co-inoculated with TKP-A3 having ACCD activity and BVB-4 lacking ACCD exposed with two different concentrations of boron (6.5mM and 7.5mM H3BO3) under saline stress (40 mM NaCl). Our findings confirm that the detrimental effects due to excess salt and boron were successfully mitigated in plants co-inoculated with the TKP-A3 as compared to BVB-4. Our results have shown that salt and boron stress significantly altered the lateral root formation, root length, chlorophyll content and vigor index of the seedlings. Interestingly, the addition of TKP-A3 significantly increased shoot length, vigor index and chlorophyll content by almost 15%, 16% and 50% respectively compared to BVB-4, indicating the importance of ACCD activity in the mitigation of salt and boron stress. Additionally, no positive effects were observed on different growth parameters when seeds were coated with BVB-4 alone. This study highlights the significance of ACCD producing PGPB over PGPB lacking ACCD to improve growth characteristics of Vigna radiata under salt and boron stress. Molecular analysis identified TKP-A3 and BVB-4 as Enterobacter quasiroggenkampii and Cytobacillus pseudoceanisediminis respectively.