Rhizobacteria Capable of Producing ACC Deaminase Promote Growth of Velvet Bean (Mucuna pruriens) under Water Stress Condition

Decreased water levels cause severe reduction in growth and yield of plants. Generally the plant growth is inhibited under water stress due to the high concentration of ethylene in the rhizosphere. Plant growth promoting rhizobacteria (PGPR) inhabiting the rhizosphere capable of producing 1-aminocyclopropane-1-carboxylate deaminase (ACCd) enzyme can also reduce the concentration of ethylene in plant by breaking down ACC, the immediate precursor of ethylene. Such PGPR were isolated from different parts of the province of Punjab and Khyber Pakhtunkhwa and screened for their ability to promote growth of velvet bean in axenic conditions. The results showed that some rhizobacterial strains significantly improved the growth of roots and shoots in normal and water stress condition. A significant increase was observed in root length (32%), shoot length (110%), root dry weight (50%) and shoot dry weight (60%) in response to inoculation compared to an uninoculated control. Four strains showed very encouraging results in promoting the growth of velvet bean. The ability of selected rhizobacteria to reduce the concentration of ethylene was confirmed by performing classical triple response bioassay in etiolated pea seedlings. The results of this study illustrate that ACCd active PGPR can be used for improving plant growth and yield of velvet bean under limited availability of water