Phaseolus vulgaris L. production in Sub Saharan Africa is affected by nitrogen deficiency in the soils. Rhizobium inoculants are considered as the best solution to curb the problem of soil nitrogen deficiency. However, accessibility of rhizobia inoculants in most African countries is a challenge, hence leads to most inoculants being imported from abroad. The estimation of the number of indigenous rhizobia nodulating P.vulgaris in the soils of Hai District, northern Tanzania as well as isolation, authentication and evaluation of the symbiotic effectiveness of those indigenous rhizobia strains was conducted. The most probable number infection method was used to estimate the population of indigenous rhizobia in the soils. Yeast Extract Manitol Agar containing congo red was used to grow the isolated rhizobia strains. Koch’s postulates were employed in authentication, while the number of nodules per plant, chlorophyll content and other plant growth parameters was used to test effectiveness of the isolated strains. The Shapiro Wilk’s W test was used for testing normality of the data, one way ANOVA and Kruskal-Wallis Ranksum test was used for analysis of the data which are normally distributed and those which are not normally distributed respectively while Fisher’s Least Significant Difference were used as a post hoc significance test. The 61% of the soil in the study area had low rhizobia populations (<100 cells g-1 of soil). Moreover, 18 bacterial strains were isolated and proved to be rhizobia. Two isolated strains (NR12 and NR13) showed higher effectiveness in nitrogen fixation than the commercial strain CIAT 899.
MSc and Bcs thesis, internship reports