Abstract
Bacteria carrying 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity lower stress induced ethylene levels and may be effective to improve plant growth under salt stress conditions. Twenty strains of rhizobacteria isolated from soil samples taken from different salt affected aras were screened for plant growth promotion and ACC- deaminase enzyme activity under axenic conditions at 6 dS rn'. Three strains (S5, S15 and S20) that promoted growth to the greatest extent under axenic conditions were selected for further study in pot trial at 0, 5, 10 dS rn'. Results of pot trial showed that the increase in salinity level decreased the growth of the maize seedlings. However, inoculation of maize seeds with these three rhizobacterial strains performed well at all salinity levels, and the strain S20 at 5 dS rn' significantly increased root/shoot length, root fresh/dry weight and shoot fresh/dry weight up to 56/62, 51/71, 52/61 %, respectively, over uninoculated control. At 10 dS rn' increase was 120/63, 52/71, 59/118%, respectively, over uninoculated control. Similarly, increase in chlorophyll a, band carotenoid contents of fresh leaves increased up to 86% at 5 dS rn' and up to 84% at 10 dS rn' by strain S20 over its respective control. Results revealed that it is highly likely that these rhizobacterial isolates deaminated endogenous ACC. Therefore, negative effects of stress induced ethylene could be partially eliminated through inoculation with ACC-deaminase containing rhizobacteria. Key words: Salt stress, ACC-deaminase, maize growth, PGPR
