This study was conducted to determine the abundance and symbiotic efficiency of native rhizobia nodulating common bean in Kisumu and Kakamega, Kenya. Soil sampling was carried out in three farms that had been used for growing common bean for at least two seasons and one fallow land with no known history of growing common bean or inoculation. Abundance of soil rhizobia and symbiotic efficiency (SE) were determined in a greenhouse experiment. Native rhizobia populations ranged from 3.2 × 101 to 3.5 × 104 cells per gram of soil. Pure bacterial cultures isolated from fresh and healthy root nodules exhibited typical characteristics of Rhizobium sp. on yeast extract mannitol agar media supplemented with Congo red. Bean inoculation with the isolates significantly (p < 0.05) increased the shoot dry weight and nitrogen (N) concentration and content. The SE of all the native rhizobia were higher when compared to a reference strain, CIAT 899 (67%), and ranged from 74% to 170%. Four isolates had SE above a second reference strain, Strain 446 (110%). Our results demonstrate the presence of native rhizobia that are potentially superior to the commercial inoculants. These can be exploited to enhance bean inoculation programmes in the region.

Aims: The study was aimed at isolating, identifying and assessing the effectiveness of indigenous rhizobia nodulating P. vulgaris in Lake Victoria Basin (LVB). Study design: Randomized complete block design. Place and Duration of Study: Soil and nodule samples were collected from Kisumu (Kenya); Kabanyolo (Uganda) and Nyabarongo (Rwanda). Field experiments: Kisumu (Kenya). Lab and greenhouse experiments: Department of Plant and Microbial Sciences Kenyatta University (Kenya) and Makerere University (Uganda). Research was carried out between January 2012 and April 2013. Methodology: Rhizobia were isolated from nodules obtained from P. vulgaris (rose coco variety) plants planted in the LVB water hyacinth compost trial fields and whole soil trapping experiments in the greenhouse using soil obtained from the LVB. The isolates were identified using morphological characteristics. Isolates from each group were used in authentication using the infection technique. Results: One hundred and twenty eight isolates were obtained from the trapping experiments and placed into nine groups based on their morphological characteristics. Four hundred and seventy two isolates were obtained from the nodules of the P. vulgaris grown in soils amended with water hyacinth compost and were placed into sixteen groups. The isolates varied in their morphological characteristics. There was a significant difference in the infectiveness and effectiveness of the representative rhizobia isolates. Conclusion: The studies revealed that rhizobia isolates from Lake Victoria are different morphologically. Authentication experiments, confirmed that the majority of the isolates were rhizobia due to their ability to infect the host plant P. vulgaris. All representative isolates varied in their ability to infect and fix nitrogen. Isolates that are more effective compared to the commercial Rhizobium leguminosarum biovar phaseoli strain 446 were identified in this study. The effective indigenous rhizobia have therefore the potential of being sources of inocula for P. vulgaris.

Cowpea ( Vigna unguiculata (L.) Walp) is an important multipurpose legume crop grown in arid and semi-arid areas of sub-Saharan Africa. The crop associates with a wide diversity of high ecological value rhizobia bacteria, improving biological soil fertility and crop production. Here, we evaluated the symbiotic efficiency (SE) and genetic diversity of native rhizobia isolated from root nodules of cowpea genotypes cultivated in semi-arid areas of lower Eastern Kenya. Rhizobia trapping and SE experiments were done in the greenhouse while genetic diversity was evaluated based on 16S rRNA gene sequencing. Twenty morphologically distinct isolates representing a total of 94 isolates were used for genetic analysis. After 16S rRNA gene sequencing, the isolates closely resembled bacteria belonging to the genus Rhizobium , Paraburkholderia and non-rhizobial endophytes ( Enterobacter , Strenotrophomonas and Pseudomonas ). This study also reports for the first time the presence of an efficient native cowpea nodulating Beta-Rhizobia ( Paraburkholderia phenoliruptrix BR3459a) in Africa. Symbiotic efficiency of the native rhizobia isolates varied (p < 0.0001) significantly. Remarkably, two isolates, M2 and M3 recorded higher SE of 82.49 % and 72.76 % respectively compared to the commercial strain Bradyrhizobium sp. USDA 3456 (67.68 %). Our results form an important step in the development of efficient microbial inoculum and sustainable food production.

The steady decline in agrobiodiversity is not only a significant threat to the genetic stability of the rural agroecosystems but also places a huge impediment to the realization of global food security. Climate change and decline in arable land is forcing subsistence farmers to abandon the less productive but well-adapted local crops for the newer short term and drought-tolerant crops decimating agrobiodiversity further. This study sought to establish the on-farm species and genetic diversity status among the family farming systems of semiarid areas of Eastern Kenya and effect on food security, agrobiodiversity management strategies, their perception of climate change, and climate change coping strategies. Structured questionnaires were administered to 92 active farmers in Embu, Kitui, and Tharaka Nithi Counties of Eastern Kenya. On-farm diversity, socio-economic factors, and their impact on agrobiodiversity were determined. Possible correlations were established using Spearman’s Rank Correlation Coefficient. Remarkably, 26 crop species were recorded where legumes and cereals were dominant. According to the Shannon–Wiener Diversity index (H′), Tharaka Nithi County recorded the highest legumes and cereals diversity indices of 3.436 and 3.449, respectively. Food shortage was reported by over 50% of the respondents in the study area. The existence of weaker adaptive measures in response to climate change was evident. Family farming systems that had higher crop diversification and integrated livestock rearing in their farms were more food secure. Improved mitigation to climate change and diversification of farming systems among the smallholder farms is essential not only in boosting the food security but also in establishment of sustainable farming systems resilient to climate change.

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