Screening of rhizobacteria containing plant growth promoting (PGPR) traits in rhizosphere soils and their role in enhancing growth of pigeon pea
Plant growth promoting rhizobacteria (PGPR) are beneficial bacteria that colonize plant roots and enhance plant growth with a wide variety of mechanisms. The use of PGPR is steadily increasing in agriculture and offers an attractive way to replace chemical fertilizers, pesticides and supplements. Here, we have isolated, enumerated and characterized the PGPR from the rhizosphere soil of pigeon pea for the enhancement of growth of pigeon pea. Rhizosphere soils were collected from different areas of Samalkot, Pithapuram, Peddapuram and Kakinada. Sixty five (65) isolates were identified and characterized for their morphological, cultural, staining and biochemical characteristics, of which 35 was selected for the screening of PGPR isolates. Sixteen isolates were successfully characterized for the PGPR traits like indole acetic acid (IAA) production, phosphorus solubilization, and production of enzymes like urease, chitinase, amylase, cellulase, protease and β-1,3 glucanase and were assayed. The antagonistic nature of these strains towards fungi and bacteria were estimated by siderophore estimation, 1-amino-cyclopropane-1-carboxylate (ACC) deaminase characterization, dual plate culture method and HCN production technique, and the best one was selected. These were further investigated to show the PGPR traits in pigeon pea seedling emergence, increase of shoot length, root length, dry matter production of shoot, nodule number and nodule mass. Furthermore, PGPR isolates remarkably increased seed germination of pigeon pea. Among the sixteen isolates, seven were found to be high
IAA producing. Six were found to be efficient phosphate solubilizers, five isolates were found to be good antagonistic towards pathogen soil fungi and eight isolates were found to be better in enzyme productions, and thus, may enhance the mineralization efficiency of soils. Three isolates were shown to be promising in IAA production, phosphate solubilization, antagonism towards fungi, and mineralizing capacity. Thus, this study suggests the use of these isolates as inoculant biofertilizers which might be beneficial for pigeon pea cultivation as they enhanced the growth and other growth parameters.
Keywords: Indole acetic acid (IAA), plant growth promoting rhizobacteria (PGPR), phosphorus solubilization, enzyme productions, seed germination