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Browsing Books/Book Chapters/Book Reviews by Author "Eunice W. Githae"

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    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. Muraya
    Many 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.
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    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. Omondi
    Nitrogen (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.
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    Status of Opuntia invasions in the arid and semi-arid lands of Kenya
    (CAB International, 2018-03-21) Eunice W. Githae
    Invasive 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.