EFFECT OF RHIZOBACTERIA ON PLANT GROWTH HORMONE PRODUCTION, PHOSPHATE SOLUBILIZATION AND GROWTH PERFORMANCE OF Phaseolus vulgaris L. UNDER IN VITRO CONDITION

Abstract

Bacterial inoculants are used as alternative bio-fertilizers due to their ability to solubilize phosphate and increase plant growth and development. Therefore, the research was conducted to isolate phosphate solubilizing rhizobacteria (PSB) from rhizosphere soil of faba bean and ground nut plants and examining their ability to solubilize phosphate and their effect on Phaseouls vulgaris seed germination and seedling growth. A total of 30 phosphate solubilization bacterial (PSB) isolates were collected from Babille, Meta and Haramaya University farm lands, Ethiopia. The laboratory experiment was based on bioassay in order to assess the seed germination percentage and seedling growth of Phaseolus vulgaris. To measure the zone of clearance for effective phosphate solubilization (PSB) as well as to examine their ability to produce Indole Acetic Acid (IAA), and the experimental design was (CRD) with factorial arrangements and three replications. The results of this study revealed the isolate PSB20 (6.250) showed the maximum solubilization index (SI), and PSB25 has the lowest SI (4.667) and PSB20 (2.967ppm) showed the highest IAA production as compared to PSB25 (2.197ppm). Among the treatments, PSB20 has a minimum date of germination (4 days) and a maximum length of plumule and radical (6.61cm) and (4.5cm) respectively. A significant reduction in day to germination was observed at PSB20 (4 days) while the maximum day to germination was observed by PSB25 (6.33 days). In the present investigation, PSB20 and PSB12 showed the better ability of solubilizing phosphate as compared to other isolates and enhance the seed germination percentage and seedling growth of Phaseolus vulgaris.