Biological Science
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Item Status of Opuntia invasions in the arid and semi-arid lands of Kenya(CAB International, 2018-03-21) Eunice W. GithaeInvasive alien species (IAS) are among the leading threats to biodiversity, food security and human well-being. Opuntia (prickly pear cactus) is one of the most widespread and naturalized in the arid and semi-arid areas of Kenya, with extreme effects on rural livelihoods and the environment. However, comprehensive information on the status of invasion in the country is lacking, which is crucial for developing strategies for prevention and management. This paper, therefore, provides an overview of the interacting factors that influence its invasion in Kenya in terms of species diversity, pathways of introduction, negative impacts and the effectiveness of regulations and control measures. Seven invasive species of Opuntia are present in the country with the most abundant (O. stricta) being under biocontrol trial. These species have the same habitat preferences, physiological traits, negative impacts, introduction pathways and management options. Invasion is mainly attributed to changes in land use and consequent land degradation. Introduction pathways are largely intentional for ornamental purposes but unintentional at a local scale through escape from gardens and natural dispersal. The most applied methods of managing Opuntia are mechanical and chemical methods that are unsustainable and labour-intensive at large scale. Effective policies are therefore needed to prevent an increase in the significant negative impacts caused by IAS including those that have a limited distribution.Item Antimicrobial activities of Tithonia diversifolia and Kigelia africana against Fusarium oxysporum in tomatoes(Chuka University (Journal of Environmental Sustainability Advancement Research), 2021) Awere, C. A.; Githae, E. W.; Gichumbi, J. M.Fusarium wilt disease caused by the soil-borne fungus Fusarium oxysporum Schlechtthe is a serious threat to tomato production worldwide. Chemical and cultural methods of management used are either ineffective or toxic to the environment. Plant secondary metabolites; therefore, pose a possible alternative because they are environmentally friendly and have minimal effect on non-target organisms. This study screened phytochemical compounds of two plants; Tithonia diversifolia and Kigelia africana and assessed their potency in controlling plant fungal pathogen F. oxysporum, the causative agent of Fusarium wilt disease in tomatoes. Leaf extracts of T. diversifolia and fruit extract of K. africana were used in this study becauses they are readly available and the plnts have been used in the treatment of varius diseases in humanbeings. The plant etract were concentrated in water and screened for phytochemical contents using standard procedures. Concentrations used were 25 g/L, 50 g/L and 100 g/L to sock the disc. Fusarium oxysporum was isolated from infected soil using potato dextrose agar media while the antifungal activity was evaluated by measuring the zone of inhibition against the test organism. In determining the antimicrobial properties of each of the plant extract, a 3×3 randomised complete block design was used, replication was done 3 times. The results showed that the mean inhibitory zones were highest at 100g/l in both plants, although K. africana fruit extract portrayed the higher inhibitory activity compared to Tithonia africana. The effect of the plant extracts and the positive control were statistically significant (pα0.05). This study indicates that K. africana and T. diversifolia possess the antifungal activity and can be used as a broad-spectrum fungicide against F. oxysporum. The effect of the plant extract was statistically significant (p<0.05). The Mean of inhibition ranged from 23.67 to 7.78 mm for Tithonia diversifolia and 23.67 to 11.75 for Kigelia africana. While for the combined extract the The Mean of inhibition ranged from 22.78 to 7.93 . The minimum reduction in sporulation was recorded in the positive control, which was significantly lower than the rest of the treatments.These plant extracts may provide an effective measure for the management of Fusarium wilt of tomatoes that may form an integral part of integrated pest management and become a prospect alternative to conventional fungicides.Item Nitrogen fixation by natural populations of Acacia senegal in the drylands of Kenya using 15N natural abundance(Taylor & Francis, 2013-06-24) Eunice W. Githae; Charles K. K. Gachene; Jesse T. Njoka; Stephen F. OmondiNitrogen (N) fixation was estimated for three Acacia senegal (L.) (A. senegal) Willd. varieties (A. senegal var. senegal, kerensis, and leiorhachis) growing naturally in different sites in the dryland areas of Kenya. The quantities of N2 fixed were estimated by the 15N natural abundance method, using leaves as the sampling material. Balanites aegyptiaca (B. aegyptiaca) was selected as the reference species growing in the same area. Soil samples were also collected under A. senegal trees for nodule assessment. Leaf 15N natural abundance values (d15N) were significantly different between A. senegal and B. aegyptiaca. These values averaged 6.35, 4.67, and 3.03% for A. senegal var. kerensis, leiorhachis, and senegal, respectively, and were lower than those of the adjacent reference species. There were also significant differences in the amount of N2 fixed (%Ndfa) among the varieties. A. senegal var. senegal showed the highest levels of N2 fixation with a mean of 36% while A. senegal var. kerensis and leiorhachis had equal estimates of 25%. However, no nodules were observed in the collected soil samples. Leaf N values were significantly different among the varieties with a mean of 2.73, 2.46, and 4.03% for A. senegal var. kerensis, leiorhachis, and senegal, respectively. This study shows that the three varieties of A. senegal are able to fix N2 in their natural ecosystems and the differences could probably be due to soil properties and nutrient availability under the different environments. The species can hence be utilized as plantations in agriculture and land rehabilitation programs.Item Efficacy of endophytic fungi isolated from Azadirachta indica roots against Alternaria causing early blight of tomato(Talenta Publisher (University of Sumatera Utara journal platform hosting service), 2023-12-01) Kennedy O. Ododa; Eunice W. Githae; Moses M. MurayaMany medicinal plants are reported to host a myriad of beneficial endophytic microbes. Among the well-known medicinal plants is Azadirachta indica (Neem; Family Meliaceae), which has gained worldwide importance due to its extensive array of therapeutic and insecticidal qualities. The use of A. indica extracts in the treatment of plant pathogens has been the subject of extensive investigation, but its endophytic microbes as potential biocontrol agents have received very little attention. In this study, the efficacy of endophytic fungi isolated from A. indica roots against Alternaria, which causes tomato early blight, was examined. Isolation and characterization of Alternaria species and endophytic fungi were done in the laboratory using standard procedures. An in-vitro assay of the endophytic fungi isolates against Alternaria was conducted in a complete randomized design in order to determine the percentage zone of inhibition. The colonies of Alternaria isolates were fast-growing, black to grayish-brown, and suede-like. The conidial length from different isolates was statistically significant (p ˂ 0.05) and ranged from 15 μm to 46 μm. The conidial widths were not statistically significant (p > 0.05) and ranged from 8 μm to 15 μm, while the conidial area ranged from 120 μm to 690 μm. A total of seven species of endophytes were isolated from the root of Azadirachta indica: Phoma, Actinomycetes, Chaetomium, Trichoderma, Verticillium, Penicillium, and Fusarium. There was a significant difference in the zones of inhibition (p ˂ 0.05), which ranged from 0.0 mm (Actinomycetes) to 3.44 mm (Trichoderma). These isolates could be used to create brand- new organic antifungal substances that are efficient against a variety of plant fungal pathogens.Item MICB 802: MICROBIAL PHYSIOLOGY(Chuka University, 2023-04-13) Chuka UniversityItem Microbial quality and safety of ready-to-eat street-vended foods sold in selected locations in Kenya(Journal of Food and Dietetics Research, 2022-01-27) Johnson Mwove1,2 , Samuel Imathiu3 , Irene Orina3 , Paul Karanja3Objectives: Street-vended foods (SVFs) are a major contributor to foodborne diseases, especially in developing countries, where their sale is largely uncontrolled. Foodborne diseases have often been linked to high morbidity and mortality in some developing countries such as Kenya, demonstrating their public health and societal significance. The objective of this study was to determine the microbial quality and safety of ready-to-eat (RTE) foods sold in selected locations within Thika town in Kiambu County, Kenya. Material and Methods: A total of 199 food samples consisting of cereals, sliced fruits, salads, groundnuts, tubers, fruit juices, boiled deshelled eggs, smokies, and sausages were randomly collected for microbial analysis. Determination of total viable count (TVC), total coliform count (TCC), yeast and molds count (YMC), Escherichia coli counts, Staphylococcus aureus counts as well as the presence of Salmonella spp., and Listeria monocytogenes were determined following standard microbiological methods. Results: Results revealed that plant-based foods had significantly (P < 0.01) higher TVC, TCC, YMC, and S. aureus counts compared to animal-based foods. The levels of TVC, TCC, YMC, E. coli, and S. aureus ranged from 6.590 ± 1.020 to 3.377 ± 1.764, 5.567 ± 2.233 to 1.594 ± 2.299, 5.052 ± 1.201 to 1.595 ± 2.146, 2.033 ± 1.229 to 0.000 ± 0.000, and 5.972 ± 1.170 to 1.888 ± 1.660 Log10 CFU/g, respectively. At least nine food samples were contaminated with E. coli although the chance for contamination was significantly (P = 0.0002) higher (15 times) in plant-based foods compared to animal-based foods. At least one sample in each food type was contaminated with S. aureus with contamination levels above 1.888 ± 1.660 Log10 CFU/g. Salmonella spp. was only detected in boiled arrowroots (25%), boiled deshelled eggs (5.6%), French fries (5.6%), juices (5.0%), and cereals (11.1%), while L. monocytogenes were not detected in any food sample. Conclusion: These findings demonstrate that RTE SVFs sold in this region constitute a potential health hazard to consumers because of the presence of Salmonella spp., and high counts of E. coli and S. aureus. These foods are, therefore, microbiologically unsafe and unsuitable for human consumption as they may cause foodborne disease outbreaks.