Abstract

                                The stem nodulating leguminous green manure Sesbania rostrata has great potential as an effective bioresource material for rice production due to higher biomass production and N, contribution. Attempts were made to extend the symbiotic N, fixation to non-legumes such as rice. The symbiont Azorhizobium caulinodans ORS 571 upon inoculation, stimulated the lateral root development as well as formation of nodular like structures in the roots of rice. Colonization of lateral root cracks by A. caulinodans ORS 571 was found to be stimulated by the flavonoid naringenin. Rice seedlings growing aseptically in the presence of naringenin were inoculated with A..caulinodans ORS 571 (pXLGD4) carrying the lac Z reporter gene. By microscopic analysis of sections of inoculated rice roots, it has been demonstrated that the xylem of rice roots can be colonized by Azorhizobium caulinodans. This could provide a suitable niche for endophytic nitrogen fixation by A. caulinodans in rice.

Key words : Azorhizobium caulinodans, Endophytic colonozation, Naringenin, Nodulation, Non-legumes, N, fixation, Sesbania rostrata, Xylem colonization