Evaluation of ACC deaminase and indole acetic acid production by Streptomyces hydrogenans DH16 and its effect on plant growth promotion

Environmental degradation caused by the unabated and indiscriminate use of agrochemicals, employed to increase the crop yields, and thus resulting in incrementing the public concern by every passing year, has invited the interest of researchers to find ever safe alternatives for enhancing the crop productivity. In the light of this, the present study undertook the research objective to explore the plant growth promoting activities of Streptomyces hydrogenans DH16, a soil actinobacterium possessing broad spectrum antifungal activity. Optimization of IAA production by S. hydrogenans DH16 using one variable at a time approach resulted in 2.24 fold (from 36 mu g/ml to 80.06 mu g/ml) increase in yield of IAA. S. hydrogenansDH16 completely utilized 1-aminocyclopropane-1-carboxylate on fourth day of incubation and showed 1-aminocyclopropane-1carboxylate (ACC) deaminase activity of 363 nano moles alpha-ketobutyrate/mg protein/h. This streptomycete also demonstrated in vitro ability to colonize plant roots, fix atmospheric nitrogen and inhibit fungal phytopathogens viz.Alternaria solani and Pyricularia oryzae. The influence of S. hydrogenansDH16 on growth of pea seedlings (Pisum sativum) was evaluated in which it significantly enhanced seed germination, shoot length, root length, fresh and dry weights and lateral roots. Similarly, treatment of seeds with culture broth containing IAA (50 mu g/ml) showed positive impact on growth of pea seedlings with 39.45-58.04% increase in various growth parameters. These results demonstrate that S. hydrogenans strain DH16 and extracellular metabolites (antifungal and plant growth promoting substances) produced by it can be exploited as soil amendment as biofungicide and biofertilizer with many advantages over the chemical fungicides and fertilizers.