Grain legumes play a significant role in smallholder farming systems in Africa because of their contribution to nutrition and income security and their role in fixing nitrogen. Biological Nitrogen Fixation (BNF) serves a critical role in improving soil fertility for legumes. Although much research has been conducted on rhizobia in nitrogen fixation and their contribution to soil fertility, much less is known about the distribution and diversity of the bacteria strains in different areas of the world and which of the strains achieve optimal benefits for the host plants under specific soil and environmental conditions. This paper reviews the distribution, characterization, and commercialization of elite rhizobia strains in Africa.

Barley (Hordeum vulgare L.) has narrow genetic base for selection of promising ideotypes for the following traits: high biomass yield for livestock feed, enhanced agronomic and nutritional traits, and resistance to biotic and abiotic stresses. Ethyl methane sulfonate (EMS) mutagenesis offers opportunities for inducing genetic variation for key traits for development of feed barley ideotypes. The objective of this study was to determine optimal EMS dosage and exposure time to induce genetic variation for selection of high biomass yield six-row feed barley mutants. Five EMS dosages (i.e. 0.1%, 0.3%, 0.5%, 0.7% and 0.9% v/v) and five exposure times (i.e. 0.5 hr, 1 hr, 1.5 hr, 2 hrs and 2.5 hrs) were used on a six-row fodder barley using a 5 x 5 factorial treatment structure in a complete randomized design with three replications. Non-treated seed were used as a comparative control. Data was recorded for percent germination, seedling survival, shoot height, root height, shoot and root biomass. Significant (p < 0.05) EMS dosage x exposure time was observed for assessed traits indicating their influence on phenotypic variation in feed barley. Overall, a declining trend was observed for assessed traits with increased EMS dosage and exposure time. The LD50 value of 0.64% (v/v) EMS dosage was identified as an optimal dose for large-scale mutagenesis protocol to select fodder barley mutants with high biomass yield

Introduction: Incorporation of inoculum in different carrier materials may increase the efficacy of bacterial inocula.Materials and Methods: Field experiments were conducted using two strains of rhizobium and phosphate‐solubilizing bacteria (PSB) and their respective combinations using different carrier materials in common bean‐growing regions in three soil types in Kenya. The field experiment was laid out in a split‐plot arrangement with the strain inoculations as the main plot while the subplots consisted of the carrier materials (filter mud, peat moss and yeast extract mannitol broth [YEMB]). Each main plot included two controls: uninoculated negative control and uninoculated controls that received N and P fertilizer. The experiment was conducted for two cropping seasons. Data were collected on the nodulation, shoot and root biomass and yield.Results: Co‐inoculation of the common bean with Rhizobium phaseoli + Bacillus aryabhattai strains had significantly higher number of nodules (55 nodules per plant) compared to single R. phaseoli inoculation (38 nodules). The co‐inoculation of the rhizobia and the PSB yielded statistically at par with the application of diammonium phosphate (18:46:0) across the soil types and seasons. The use of filter mud as a carrier material led to a higher number of nodules for most of the rhizobia strains inoculation and their respective co‐inoculation with the bacillus strains. Significantly higher yield was obtained with the filter mud (1.64 Mg ha⁻¹) while there was no significant difference in the yield of common bean between peat moss and YEMB as carrier materials for the bacterial strains.Conclusion: The solid carrier material, specifically filter mud, showed potential for use in the formulation of inoculants. Specific co‐inoculation of rhizobia (R. phaseoli and Rhizobium pusense strains) and PSB (Paenibacillus polymyxa and B. aryabhattai) increased the growth, nodulation and yield of common bean more efficiently than the control.