Abstract
Rhizobia are bacteria well known for biological nitrogen fixation through symbioses. These bacteria may also perform as plant growth promoting rhizobacteria (PGPR). In this study the role of rhizobia as PGPR was studied. Rhizobia was isolated from the root nodules of various summer legumes including Glycine max (Soybaen), Vigna radiata (Mung bean), Vigna unguiculata (Cowpea), Susbenia grandiflora (Sesbania) and Cymposistetra gonoloba (Guar) grown at New Developmental Farm (NDF), the University of Agriculture Peshawar, Pakistan during summer 2011. Rhizobia were isolated from root nodules by using yeast minitol agar media, pure culture of each isolate was prepared and examined for various PGPR traits. Data revealed that 9, 83, 47 and 21% of tested strains were found to produce cyanide (HCN), siderophores, indole-acetic acid (IAA) and solubilized phosphorus respectively. Among the tested rhizoial isolates, rhizobia isolated from Vigna radiata showed highest PGPR activity fallowed by Glycine max while relatively lower PGPR activity was observed for rhizobial isolates of Cymposistetra gonoloba (Guar). All the tested isolates were gram negative. Soybaen and cowpea isolates were found to be fast growing while mung bean, susbenia and guar were slow growing in nature. This study indicates that rhizobial isolates of Vigna radiata and Glycine max have the capability to be used as PGPR.
Highlights
Rhizobia are bacteria well known for biological nitrogen fixation through symbioses
Rhizobia was isolated from the root nodules of various summer legumes including Glycine max (Soybaen), Vigna radiata (Mung bean), Vigna unguiculata (Cowpea), Susbenia grandiflora (Sesbania) and Cymposistetra gonoloba (Guar) grown at New Developmental Farm (NDF), the University of Agriculture Peshawar, Pakistan during summer 2011
Among the tested rhizoial isolates, rhizobia isolated from Vigna radiata showed highest plant growth promoting rhizobacteria (PGPR) activity fallowed by Glycine max while relatively lower PGPR activity was observed for rhizobial isolates of Cymposistetra gonoloba (Guar)
Summary
Few drops of Congo red were added into flask containing media. Growth of colonies Several of rhizobium clusters were appeared within 3-4 days (fast growing) while some were seemed within 7-8 days (slow growing) These colonies were identified as rhizobium having milky color (mucoid), round shape without picking the color of Congo red on YMA. Obtaining the pure culture The desired microbial growth was chosen with the help of pasteurized loop from the pre prepared plate, and streaked in sterilized glass tubes containing YMA media aseptically. The bottles were properly marked and placed in the incubator at 28-30 °C for incubation in order to increase the biomass of pure culture. The rhizobial colonies from the bottle culture were poured in pre sterilized carrier material that may either be peat soil or completely decomposed farm yard manure at the rate of 85-100 mL per 0.5 kg peat soil. The bacteria were considered as phosphate solubilizers by production of clarification halos on di calcium phosphate agar plates [21]
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