ACC deaminase producing bacterium Enterobacter cloacae ZNP-2 mitigate salinity stress and enhance salinity stress tolerance in wheat plant

Department of Biotechnology, Jaypee Institute of Information Technology Noida, Uttar Pradesh, India

Abstract

Increasing soil salinity adversely affects plant growth and productivity. However, some salt-resistant rhizosphere bacteria have the possible ability to increase the growth of plants when put under saline stress conditions. Among ACCD (ACC deaminase)-producing bacteria which have been extracted from the rhizosphere of plants growing in salt-rich desert soil, ZNP-2 was selected based on its ability to produce phytohormone and ammonia, and solubilize phosphate, and further identified as Enterobacter cloacae. Furthermore, we evaluated the protective effects of the inoculation of Enterobacter cloacae ZNP-2 on morphological and physiological growth parameters, ionic balances, accumulation of osmolytes, and antioxidative defense system under both normal and salt stress conditions. Through polymerase chain reaction, the presence of AcdS gene, which is responsible for the structural gene for ACCD was confirmed for the strain ZNP-2. The increase in saline stress leads to accumulation of toxic Na⁺ and decrease in levels of K⁺, thereby favoring the KTNa⁺ ratio. Moreover, ZNP-2-inoculated plants showed improvements in biomass (13% to 31%) and chlorophyll contents (25% to 51%) as compared to the un-inoculated plants. ZNP-2 inoculation also improved the various osmolytes in wheat plants to maintain the osmotic balance. The observation implies that ZNP-2 isolate augments salt tolerance in wheat plants by modulating the intracellular level of various osmolytes. Therefore, the utilization of beneficial microbial isolate as a mechanism for inducing salt tolerance in wheat plants could be used as an effective tool to combat salt stress in plants.