Isolation and characterization of nitrogen deficit Rhizobium isolates and their effect on growth of haricot bean

Abstract

Nitrogen deficiency in recognized as the limiting factor for reduction in the yield of haricot bean in Ethiopia. The nitrogen fixing bacteria have the ability to enhance the plant growth and yield by fixing the atmospheric nitrogen and also play a significant role to conquer this problem. The aim of study was to isolate and characterize the haricot bean nodulating Rhizobium isolates and also to evaluate their effect on the growth of haricot bean. Out of total, twelve isolates were selected as representative samples and were screened for morphological, physiological and biochemical characteristics. On the basis of screening, eight potential isolates (MJUML1, MJUML3, MJUML4, MJUML6, MJUML8, MJUML10, MJUML11 and MJUML12) were selected for the further greenhouse experiment. The result indicated that inoculation of plants with Rhizobium isolates have significant effect on shoot dry weight, shoot nitrogen contents, nodule numbers, and nodule dry weight per root system (p < 0.05). Among all the tested Rhizobium isolates, MJUML11, MJUML12 and MJUML1 were best isolates and significantly increased the growth of haricot bean in nitrogen deficit soils and also survive in the soil as saprophytes. Key words: Biological nitrogen fixation, Nitrogen content, N-deficit soil, Phaseoulus vulgaris.