Study of Stress Tolerant Forms of Rhizobia  Isolated from Trigonella Foenumgraecum.  in Semi Arid Region of Rajasthan

Abhi Garg; Manoj Sharma

Volume : II, Issue : III, March - 2013

Study of Stress Tolerant Forms of Rhizobia Isolated from Trigonella Foenumgraecum. in Semi Arid Region of Rajasthan

Abhi Garg, Manoj Sharma

Abstract :

Rhizobia, a group of symbiotic nitrogen fixing bacteria plays a remarkable role in cycling of nitrogen. They are gram negative, motile rod shaped bacteria. In this study, attempts have been made to evaluate the effect of abiotic stresses (Salt, pH, Temperature, metal tolerance ) on growth of Rhizobia. Ajmer being a semi arid zone of Rajasthan was selected for the study of stress tolerant forms of Rhizobia isolated from Trigonella foenumgraecum. Ten bacterial forms were isolated and screened for stress tolerant forms. Phenotypic and biochemical characterization of all the isolates were done followed by their plant assay test in growth pouches. Growth of isolates on yeast mannitol medium having variable range of pH (4–10) and different concentration of NaCl (0.05%–5%) were determined. Temperature tolerant isolates were also selected. 4 isolates( RTF1,RTF–2,RTF–5,RTF–10) were found salt tolerant and 5 forms (RTF–1,RTF–2,RTF–3,RTF–9,RTF–10)were found pH tolerant and forms (RTF–1,RTF–2,RTF–3,RTF–5,RTF–7,RTF–8) were found temperature tolerant. Rhizobia with a high negative charge were found to be better protected in dry soils. Metal tolerant strains were also evaluated. It can be concluded from the study that these stress tolerant property of Rhizobia have enormous potential to be used as biofertilizers especially where the environmental constrains act as limiting factors and impose restrictions on growth of the host legumes and can also be used during forestation of degraded areas in adverse environmental conditions.