1-Aminocyclopropane-1-carboxylate (ACC) Deaminase-Producing Endophytic Diazotrophic Enterobacter sp EN-21 Modulates Salt-Stress Response in Sugarcane

Soil salinity is a wide-reaching environmental problem that lowers the yield of commercial crops such as maize, rice, and sugarcane. In this study, we examined the effect of 1-aminocyclopropane-1-carboxylate (ACC) deaminase-producing endophytic diazotrophic Enterobacter sp. EN-21 on growth promotion, salt tolerance, and root colonization of sugarcane. Enterobacter sp. EN-21 inoculated and uninoculated sugarcane plants were grown in a greenhouse with and without 200 mM NaCl for 7 days. Sugarcane inoculated with Enterobacter sp. EN-21 substantially increased in total plant length, dry, and fresh weights in both non-salt and salt treatments. Under the salt-stress condition, Enterobacter sp. EN-21 significantly reduced proline, malondialdehyde, ethylene emission, and Na+ accumulation in sugarcane but markedly increased total chlorophyll content and K+ accumulation. The gfp-tagged Enterobacter sp. EN-21 was observed to colonize early at the root cap, root hairs, and lateral root junctions of sugarcane and later localized in intercellular spaces. Altogether the results of this study indicated that ACC deaminase-producing Enterobacter sp. EN-21 is a true endophyte and able to promote growth and enhance salt tolerance in sugarcane.