Symbiotic Properties of Rhizobial Isolates of Manang and Kathmandu Districts

Abstract

Nitrogen is a major limiting factor for primary production in any ecosystem and also the vital component of nucleic acids, proteins, chlorophylls and many other metabolic molecules. Legume-Rhizobium symbiotic system is known to be an efficient converter of ambient nitrogen into its nutrient form that increases soil fertility. The present work involved isolation, characterization and authentication of two rhizobial isolates, KR1 and MR2 obtained by trap method using broad bean (Vicia faba L.) from the field soils of Kathmandu and upper Manang (trans-himalayan region). Their culture characters and symbiotic effectiveness were analysed using standard methods. V. faba was used to study their effectiveness on various parameters such as plant height, roots length, shoot length, nodule number, nodules biomass, plant biomass, content of ureides in xylem sap, as indicative to fixed nitrogen and total nitrogen in nodules, stem and leaves were studied. Viable cell counts at 72h of growth were 17.8x10⁷ for MR2 and 14.1x10⁷ for KR1. The isolates were similar for nodulation, plant biomass and nodule nitrogen (P≥0.05) the MR2 affected vigorous plant growth. However, the isolates showed significant differences (P≤0.05) with plant age on all the parameters studied. The kinetics of inoculation effects on nodulation, plant height, biomass, and total nitrogen were dealt with.

Key words: Rhizobium; rhizobial isolates; nodules; translocation

DOI: 10.3126/njst.v11i0.4130

Nepal Journal of Science and Technology 11 (2010) 95-100