Browsing by Author "Eunice W. Githae"

Now showing 1 - 8 of 8

Biological control of desert locust (Schistocerca gregaria Forskål)
(CABI (CAB International), 2021-01-05) Eunice W. Githae; Erick K. Kuria
Desert locust (Schistocerca gregaria Forskål) is one of the most serious agricultural pests in the world due to its voracity, speed of reproduction, and range of flight. We discuss the current state of knowledge on its biological control using microorganisms and botanical extracts. Metarhizium flavoviride was among the first fungus to be recognized as a bio-control agent against desert locust in the laboratory and field conditions. Nevertheless, its oil formulation adversely affected nontarget organisms, hence led to further research on other microorganisms. Metarhizium anisopliae var. acridum (syn. Metarhizium acridum) is an environmentally safer bio-pesticide that has no measurable impact on non-target organisms. However, there are various shortcomings associated with its use in desert locust control as highlighted in this review. Bacterial pathogens studied were from species of Bacillus, Pseudomonas, and Serratia. Botanical extracts of 27 plant species were tested against the locust but showed varied results. Azadirachta indica and Melia volkensii were the most studied plant species, both belonging to family Meliaceae, which is known to have biologically active limonoids. Out of the 20 plant families identified, Apiaceae was the most represented with a frequency of 21%. However, only crude botanical extracts were used and therefore, the active ingredients against desert locust were not identified. Through a comprehensive research, an integrated pest management strategy that incorporates these bio-controls would be a realistic option to control desert locust infestations.
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.
Implication for in situ conservation of indigenous species with special reference to wild Coffea arabica L. population in Mount Marsabit Forest, Kenya
(Universidad Autónoma de Yucatán (UADY), 2011) Eunice W. Githae; Charles K. K. Gachene; David W. Odee
Mt. Marsabit forest is the only forest in Kenya where Coffea arabica L. (Rubiaceae) occurs naturally in wild populations. This forest however is highly fragmented and decreasing at a rapid rate due to anthropogenic activities. This study assesses the diversity and structure of species of conservation concern with reference to wild coffee as basis for management, conservation and use of wild genetic resources in Kenya. A botanical inventory and diversity study identified 52 species of trees and shrubs, 12 species of herbs and six species of climbers and lianas were recorded and belonged to 35 families and 64 genera. Rubiaceae (Coffee family) was the richest family with nine species followed by Euphorbiaceae with six species. Rinorea convallarioides (Bak.f.) Eyles ssp. marsabitensis Grey-Wilson (Violaceae), an endemic species, and Drypetes gerrardii Hutch. (Euphorbiaceae), were the two most important species, accounting for more than third of the combined importance value. Coffea arabica was dominant in the forest undergrowth with a higher density occurring in the open patches where it was competing with other shrubs and small trees in the undergrowth. The success and future management and conservation strategy of this forest depend on how to conserve the forest genetic resources especially of this wild species.
Influence of Socio-economic Factors on Prevalence of Ochratoxin A in Dry Coffee Cherry in Tharaka Nithi County, Kenya
(Kenya Horticultural Society, 2024-12) Tabitha K. Gitonga; Eunice W. Githae; Moses M. Muraya; Olivia A. Njiri
Coffee is a vital cash crop worldwide, contributing significantly to foreign exchange earnings and offering potential health benefits. However, concerns over contamination with mycotoxins, particularly Ochratoxin A (OTA), have grown due to its serious health risks. This study investigated the influence of socioeconomic factors on the prevalence of OTA in dry Coffee Cherry from Tharaka Nithi County, Kenya. A cluster random sampling method was used to collect the dry coffee cherry samples and survey data from 143 farmers across three agroecological zones, employing a semi-structured questionnaire. Pathogens were isolated on Potato Dextrose Agar (PDA) media and OTA production assessed according to the International Commission on Microbiological Safety for Foods. Data was analysed using the SPSS version 28 and SAS version 9.4. The study found out that socio-economic factors significantly (p < 0.05) influenced coffee farming practices and prevalence of OTA. Ochratoxin A prevalence was strongly associated with agro-ecological zones, farm size, and altitude. Larger farms and lower altitudes were linked to higher OTA risks. Gender, farm size and coffee variety also influenced OTA contamination levels. The study revealed that 88.3% of coffee farmers recognized mold in dry coffee cherries, yet 22.8% consuming moldy cherries, with 64.1% unaware of the health risks. Additionally, 87.6% of farmers identified poor drying and storage practices as key contributors to OTA contamination. Key indicators of contamination included discoloration, moldy smell, and moldiness with wetness. Roasting practices varied, with 35.1% roasting dried cherries after fermentation. The study highlights significant socioeconomic factors influencing OTA contamination in coffee. To mitigate risks, it is recommended to improve farmers' awareness of mold-related health risks and implement targeted interventions in high-risk areas to reduce OTA prevalence.
Long-distance gene flow in Acacia senegal: Hope for disturbed and fragmented populations
(Wiley, 2023-06-29) Stephen F. Omondi; Eunice W. Githae; Damase P. Khasa
Even though pollen and seed dispersals are some of the important factors that determine tree species survival across landscapes, gene dispersal data of important tropical dryland tree species such as Acacia senegal that are undergoing various population disturbances remain scarce. Understanding patterns of gene dispersal in these ecosystems is important for conservation, landscape restoration and tree improvement. We investigated pollen and seed mediated gene flow in two A. senegal populations of contrasting state (less disturbed and heavily disturbed) using nine microsatellites and 128 genotyping-by- sequencing single nucleotide polymorphism (SNPs) multilocus genotypes of two growth stages (juvenile and adult trees) and their spatial locations. We performed parentage assignments using likelihood approach and undertook spatial genetic structure (SGS) analyses for the two growth stages through correlation among kinship coefficients and geographical distances between pair of individuals. The SNPs showed higher resolving power and assignment rates than microsatellites; however, a combination of the two marker-types improved the assignment rate and provided robust parentage assessments. We found evidence of long-distance (up to 210 m) pollination events for both populations; however, the majority of seed dispersal was found closer to the putative maternal parent. On average, parentage analysis showed high amounts of pollen (40%) and seed (20%) immigration in both populations. Significant positive SGS was found only for the adult cohorts in the less disturbed population for distance classes 20 and 40 m, indicating historical short-distance seed dispersals. Our results suggest long-distance gene flow within the species and we recommend conservation of remnant and isolated populations or individual trees to promote genetic connectivity.
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.
Soil physicochemical properties under Acacia senegal varieties in the dryland areas of Kenya
(Academic Journals, 2011-08) Eunice W. Githae; Charles K. K. Gachene; Jesse T. Njoka
Acacia senegal is a multipurpose drought-tolerant tree or shrub legume and is commonly used in agroforestry systems in sub-Saharan Africa for gum arabic production and soil fertility improvement. Despite its wide distribution in Kenya, there has not been exhaustive evaluation on the effects of the extant varieties (kerensis, leiorhachis and senegal) on soil properties under their canopies for sustainable utilization of the species. Three sites in the drylands of Kenya representing the three varieties were selected for assessment. Soil samples were collected under tree canopies at a depth of 0 to 25 cm and were compared with the soils from the open canopies. There were significant differences in soil physicochemical properties among the three varieties (P<0.05 and P< 0.01). Soil nutrients under the canopies were higher than in the open canopies mainly due to effects of litter accumulation. The three varieties have beneficial effects on soil nutrient status in their natural ecosystems and would most likely improve crop productivity in agroforestry systems as well as enhance herbage productivity in the rangelands. The varieties growing under different soil types may have an effect on their gum Arabic production and quality.
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.