SCREENING OF MULTI-TRAITS RHIZOBACTERIA TO IMPROVE MAIZE GROWTH UNDER AXENIC CONDITIONS - M. I. Hussain; H. N. Asghar; M. Arshad; M. Shahbaz (Journal of Animal and Plant Sciences, 2013)
Soil microorganisms are helpful to improve the plant growth by different mechanisms like solubilization of inorganic phosphorus through production of organic acids or mineralization of organic P through phosphatase enzyme. Rhizobacteria are also capable to produce different growth regulators and enzymes. Now the challenge is isolation and screening of such multi-traits bacteria. To accomplish this task, different bacterial strains were isolated from the rhizosphere of maize. Along with their P solubilization/mineralization capabilities, bacteria were also tested for their auxin producing efficiency and ACC-deaminase activity to correlate these traits with P solubilization and ultimately screen the most efficient plant growth promoting rhizobacteria (PGPR). Out of seventy two bacterial isolates tested on Pikovskaya agar media, thirty isolates which showed clear zone (P-solubilizers) were initially selected. Out of these thirty bacterial isolates, fifteen showing higher phosphatase activity, ACC-deaminase activity and auxin production in liquid culture were selected for further evaluation for their growth promoting activities under axenic conditions. Inoculation with selected bacteria significantly increased shoot length, root length, shoot fresh and dry weight, root fresh and dry weights up to 39.7, 58.9, 99, 69.4, 97.7 and 87%, respectively over uninoculated control. Statistical analysis revealed that a positive correlation existed between the PGPR showing efficient plant growth and their in vitro traits of phosphatase activity, auxin production and ACC-deaminase activity. Study demonstrated that selection of multi-traits bacteria could be more effective tool to select PGPR than single trait to improve plant growth.
Keywords: journal article; Screening; rhizobacteria; growth regulators; enzymes