Population Estimation Of Some Rhizobia From Soilsamples Collected From High Himalayan Habitats Of Manang,Nepal

Abstract

Rhizobium meliloti, R. leguminosarum bv. phaseoli, R. leguminosarum bv. trifolii, and Bradyrhizobium spp. were isolated from the root nodules of Argyrolobium roseum, Phaseolus vulgaris, Trifolium repens and Indigofera spp. respectively from Manang. All the four rhizobial strains were isolated and purified using Yeast extract Mannitol Agar (YEMA) medium and characterized depending upon their growth responses on YEMA-CR medium, YEMA-BTB medium, YEMB medium, Gram staining and rate of multiplication of the bacterial cells. All the isolates were authenticated by using their specific host plant by infection test on sterilized filter paper and plastic pouch using modified Jensen's nitrogen free medium. The bacterial population of R. meliloti, R. leguminosarum bv. phaseoli, Bradyrhizobium spp. and B. japonicum was analyzed for each altitude ranging from Khangsar Goth (4190m asl) to Chame (2705m asl) with an altitude difference of about 100m. The effectiveness of R. meliloti, R. leguminosarum bv phaseoli, Bradyrhizobium spp. and B. japonicum was determined on the basis of total nitrogen content of the root nodules of Trigonella corniculata, Phaseolus vulgaris, Dolichos lablab and Glycine max respectively grown separately in soil of Manang and Kathmandu and showed that R. leguminosarum bv. phaseoli was the most effective one among others. Soil in each altitude was analyzed on the basis of pH, moisture, nitrogen, phosphorus, potassium and organic matter content and that overall content was satisfactory for the growth and distribution of bacterial cells. The statistical analysis also revealed the significant relationship between the altitude and no. of bacteria. The bacterial population decreased with an increase in altitudes.