Interactive effects on ACC deaminase activity in salt-tolerant plant growth-promoting rhizobacteria and impacts on rice crop improvement

Abstract

The present study focuses on the 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase assay and the rhizospheric interactions affecting enzyme activity. We investigate the efficacy of ACC deaminase-producing rhizobacterial activity in alleviating salt stress in rice. Among the five selected isolates, only two strains, KFSC2 and PK7, possessed the enzyme activity. The amplification of the acdS gene resulted in gene identification in all five isolates. The newly designed primer in this study was suitable for both Pseudomonas and Enterobacter species. The gene products of KFSC1 and KFSC2 were amplified, sequenced and subsequently submitted to GenBank with accession numbers OQ703930 and OQ798805, respectively. This marks the first-ever submission of the acdS gene sequence from Pseudomonas aeruginosa to GenBank. The interactive effect of root exudates on ACC deaminase activity was assessed using amino acids, organic acids and sugars. The highest enzyme activity was obtained with aspartic acid and fructose, while organic acids and varying pH levels had negative influences on enzyme activity. Additionally, salt and proline had positive effects. These results indicate that there is a positive interaction occurring among these compounds from plants and root-colonizing bacteria. The selected strain PK7 had a significant impact on growth parameters. Moreover, yield resulted in 252 kg/hec over the control suggests its future possibility of promising bioformulations.