John Muoma

Symbiotic Efficiency of Native Rhizobia Nodulating Common Bean (Phaseolus vulgaris L.) in Soils of Western Kenya.

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.

Morphological Assessment and Effectiveness of Indigenous Rhizobia Isolates that Nodulate P. vulgaris in Water Hyacinth Compost Testing Field in Lake Victoria Basin

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. Original Research Article British Journal of Applied Science & Technology, 4(5): 718-738, 2014 719 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 characterized using morphological features. 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 isolated in this study. The effective indigenous rhizobia have therefore the potential of being sources of inocula for P. vulgaris.

Genetic Diversity of Cowpea (Vigna unguiculata (L.) Walp.) Accession in Kenya Gene Bank Based on Simple Sequence Repeat Markers

Increased agricultural production is an urgent issue. Projected global population is 9 million people by mid of this century. Estimation projects death of 1 million people for lack of food quality (micronutrient deficit) and quantity (protein deficit). Majority of these people will be living in developing countries. Other global challenges include shrinking cultivable lands, salinity, and flooding due to climate changes, new emerging pathogens, and pests. These affect crop production. Furthermore, they are major threats to crop genetic resources and food security. Genetic diversity in cultivated crops indicates gene pool richness. It is the greatest resource for plant breeders to select lines that enhance food security. This study was conducted by Masinde Muliro University to evaluate genetic diversity in 19 cowpea accessions from Kenya national gene bank. Accessions clustered into two major groups. High divergence was observed between accessions from Ethiopia and Australia and those from Western Kenya. Upper Volta accessions were closely related to those from Western Kenya. Low variation was observed between accessions from Eastern and Rift Valley than those from Western and Coastal regions of Kenya. Diversity obtained in this study can further be exploited for the improvement of cowpea in Kenya as a measure of food security.

Genetic Characterization of Rhizosphere Bacteria that Inhabit Common Bean Nodules in Western Kenya Soils

Background: With the increasing world population, there is increasing demand for food. This has led to overuse of agricultural farms causing reduced soil fertility and accumulation of phytopathogens. Inorganic fertilizers and pesticides have been extensively used in response to these challenges. Extensive integration of inorganic fertilizers and pesticides in the farming system has contributed to soil and water pollution worsening the eutrophication in rivers lake waters. Alternative farming methods are therefore necessary to address this problem. Recent studies have found that rhizobacteria that colonize nodules of leguminous plants are capable of increasing yield and health of the tested plants. Their plant growth promoting ability depends on the rhizobacteria type, soil properties, and climatic conditions. The aim of this study, therefore, was to genetically characterize rhizobacteria that closely associate with common bean nodules by analyzing the nucleotide sequence of 16SrRNA gene. Results: The 16SrRNA gene analysis revealed that common bean nodule associated bacteria in Western Kenya soils are genetically diverse as indicated by the evolutionary genetic distances. Not even organisms in the same species had zero genetic distance though they formed independent groups on the phylogenetic tree. The isolates belonged to the genus Pseudomonas, Providencia, Rhizobia, Klebsiella, Enterobacter, Delfitia and Acinetobacter as identified through nucleotide BLAST at the NCBI GenBank database. Conclusion: Rhizobacteria that colonize common bean nodules are genetically diverse. Those found in this study may be adaptable to Western Kenya soils and further tests are required to determine their plant growth promoting efficiency.

Effects of Soil Chemical Characteristics on the Occurrence of Entomopathogenic Nematodes

Aims: This study was conducted to determine the effect of selected soil chemical characteristics on the occurrence of entomopathogenic nematodes (EPNs) under different land uses in Embu and Taita districts in Kenya. Study Design: The sampling points were systematically marked in a grid-mesh construction using GPS marking. Place and Duration of Study: Soil sampling was done between January 2008 and May 2008 in Embu district in the highlands of Central and Taita-Taveta district in the Coastal Original Research Article British Journal of Applied Science & Technology, 4(16): 2333-2343, 2014 2334 highlands of Kenya. Methodology: EPNs were baited from soil using Galleria mellonella larvae and infective juveniles identified using morphologicalbiometric characteristics. The nematode occurrence was evaluated through relative abundance and recovery frequency expressed as percentage from the soils. Results: EPNs were detected in 43.3% of the samples with Steinernema spp being the dominant species. The occurrence of EPNs is affected by selected soil chemical properties, land use systems and heavy metals. Conclusion: Soil fertility management practices and heavy metals influence the occurrence of EPNs and should be considered for their effective use as biological control agents.

Soil Maize Cultivar-related Challenges on Striga hermonthica Infested Fields in Western Kenya

Maize production in Western Kenya is constrained by Striga hermonthica and declining soil fertility. Integrated Striga Management (ISM) packages have been proposed. An ISM field experiment assessed combination of 4 maize varieties with 5 levels of soil fertility amendments. Imazapyr Resistant (IR) maize and local yellow seed Shipindi had highest germination percentages of 90% and 81% respectively, compared to commercial white seed Duma and local white seed Rachar. Duma had significantly large plants in terms of leave size and plant height; and taking least time to silking and tasseling while producing heaviest cobs and grains per plant. Synthetic fertilizer (DAP+CAN) was associated with the least germination percentage, but produced the largest plants with many leaves, took the shortest time to silking, and produced highest cob weight and grain weight, with very low S. hermonthica infestations regardless of the maize varieties. Cattle manure (CM) and water hyacinth compost containing cattle manure culture (HCM) and Effective Microbes™ (HEM) had the highest S. hermonthica population per unit area. Maize grown with water hyacinth compost containing Effective Microbes™ (HEM) positively influenced cob weight than those receiving cattle manure (CM) and the controls; while being associated with the highest numerical increase in grain yield/area. Alternative soil fertility interventions based on these observations are therefore proposed.

Effect of nitrogen sources on the yield of common bean (Phaseolus vulgaris) in western Kenya

ABSTRACT Depletion of soil nutrients due to continuous cultivation without adequate external fertilization is one of the challenges facing many smallholder farmers in western Kenya. This study was conducted to assess the effects of organic (water hyacinth compost), inorganic (urea) nitrogen (N) sources, and commercial Rhizobia inoculant on the yield of common bean (Phaseolus vulgaris) for two consecutive seasons in the short rains (2013) and long rains (2014). The experiments were laid out in a randomized complete block design and replicated four times. Triple superphosphate was applied to all treatments except those with compost to ensure that the soil had adequate phosphorus (P). Yellow and Rose coco bean varieties grown with urea and inoculated with commercial Rhizobia inoculant gave significantly higher yield of 382 kg ha−1 and 341 kg ha−1, respectively in the short rains (SR) season. In the long rains (LR) season bean yield was high in water hyacinth compost (1526 kg ha−1) and control with non-limiting P (1300 kg ha−1) treatments. Commercial Rhizobia inoculant did not significantly increase in yield in the SR and LR seasons. There was no significant influence on soil properties after two seasons of continuous cultivation of common bean and application of organic and inorganic fertilizers. These results demonstrate that water hyacinth compost improved bean yield in the LR season. However, longer field testing and economic analysis are required for it to be recommended as a substitute for inorganic N source among smallholder farmers.