Enhanced chickpea growth-promotion ability of a Mesorhizobium strain expressing an exogenous ACC deaminase gene

Aims The main goal of the study reported herein was to assess the nodulation performance of a Mesorhizobium strain transformed with an exogenous ACC deaminase gene (acdS), and its subsequent ability to increase chickpea plant growth under normal and waterlogged conditions. Methods The Mesorhizobium ciceri strain LMS-1 was transformed with the acdS gene of Pseudomonas putida UW4 by triparental conjugation using plasmid pRKACC. A plant growth assay was conducted to verify the plant growth promotion ability of the LMS-1 (pRKACC) transformed strain under normal and waterlogging conditions. Bacterial ACC deaminase and nitrogenase activity was measured. Results By expressing the exogenous acdS gene, the transformed strain LMS-1 showed a 127% increased ability to nodulate chickpea and a 125% promotion of the growth of chickpea compared to the wild-type strain, under normal conditions. Plants inoculated with the LMS-1 wild-type strain showed a higher nodule number under waterlogging stress than under control conditions, suggesting that waterlogging increases nodulation in chickpea. No significant relationship was found between ACC deaminase and nitrogenase activity. Conclusions The results obtained in this study show that the use of rhizobial strains with improved ACC deaminase activity might be very important for developing microbial inocula for agricultural purposes.