Received: 12th May 2019; Accepted: 20th June 2019

Abstract

Ethylene is a gaseous phytohormone regulating plant growth at all stages commencing from seed germination and development and extending to senescence. It is also a stress responsive hormone regulating responses of plants to abiotic and biotic stress conditions. The hormone has been associated with stress-induced senescence in plants and manipulation of ethylene synthesis is known to affect plant stress tolerance. 1-aminocyclopropane-1-carboxylate (ACC) deaminase is a bacterial enzyme that has been known to influence plant ethylene production by degrading the immediate precursor of ethylene biosynthesis specifically ACC, into ketobutyrate and ammonia resulting in reduced ethylene production during stress. In the present study, an ACC deaminase producing bacteria isolated from rhizosphere of rice and identified as Rhizobium sp was able to show ACC deaminase activity of 2.52 ± 0.73µM α- ketobutyrate /µg protein/24h. The bacterium was observed to partially offset the negative effects on seedling growth which occurred due to the presence of 3mM ACC in the growth medium. Rice seeds treated with Rhizobium sp showed highest germination percentage and vigour index under heat stress at 45 o C, when compared to uninoculated control.