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Maritim T.K.,Tea Research Foundation of Kenya | Maritim T.K.,Egerton University | Kamunya S.M.,Tea Research Foundation of Kenya | Mireji P.,Egerton University | And 4 more authors.
Journal of Horticultural Science and Biotechnology | Year: 2015

A study to determine the physiological and biochemical responses of eight tea [Camellia sinensis (L.) O. Kuntze] cultivars to water-deficit stress was conducted in a ‘rain-out shelter’ using potted plants. Three levels of soil moisture content [34, 26, or 18% (v/v) water] were applied to three plants of each cultivar in a complete randomised design, and the whole experiment was replicated three-times. The treatments were applied for 12 weeks, during which time plant water status, shoot extension rates, changes in gas exchange parameters, and leaf proline and glycinebetaine concentrations were determined. The imposition of severe water-deficit conditions [18% (v/v) soil water content] caused a significant (P ≤ 0.05) decline in the relative water content of leaves, shoot water potentials, and shoot extension rates from mean values of 84.8% to 50.6%, -0.80 to -1.15MPa, and 1.87 to 0.29 mm d-1, respectively, compared to plants grown in a well-watered soil [34% (v/v) soil water content]. The three gas exchange parameters measured (stomatal conductance, evapotranspiration rate, and rate of net photosynthesis) also declined significantly (P ≤ 0.05) with decreasing soil moisture content. In contrast, water-deficit stress increased the accumulation of leaf proline and glycinebetaine from mean values of 0.104 to 0.244 µmol g-1 FW, and from 1.567 to 2.025 µmol g-1 DW, respectively. The eight tea cultivars differed significantly (P ≤ 0.05) in their responses to water-deficit stress. Proline accumulation was significantly (P ≤ 0.05) higher in the drought-tolerant cultivars, ‘TRFK 306’, ‘TRFCA SFS150’, and ‘EPK TN14/3’, suggesting that proline concentration could be used as a marker for drought-tolerance in tea. © 2015 Headley Brothers Ltd. All rights reserved. Source


Mcharo M.,Association for Strengthening Agricultural Research in Eastern and Central Africa | Mcharo M.,Louisiana State University | LaBonte D.R.,Louisiana State University
Euphytica | Year: 2010

A population that consisted of F1 half-sibs and their parents was replicated in field plantings to generate roots to identify AFLP molecular markers and compare statistical models for selection of trait-linked markers using β-carotene content as the grouping variable. Genotypes were grouped into high and low β-carotene classes based on hierarchical cluster analysis. Association parameters between the high and low phenotypic classes of β-carotene and molecular marker profiles were made using logistic regression and discriminant analysis. Logistic regression selected 8 markers less that were associated with β-carotene content compared to discriminant analysis. Further analysis showed that logistic regression achieved 100% correct classification with the 9 markers selected compared to 17 markers that were required by discriminant analysis thus making logistic regression more efficient than discriminant analysis. Logistic regression based on Frequentist hypothesis testing differs from Bayesian based discriminant analysis. This difference may account for the percent correct classification observed. © 2010 Springer Science+Business Media B.V. Source


Wanjala B.W.,Kenya Agricultural Research Institute | Wanjala B.W.,Egerton University | Obonyo M.,Egerton University | Wachira F.N.,Egerton University | And 7 more authors.
AoB PLANTS | Year: 2013

Napier grass is an important forage crop for dairy production in the tropics; as such, its existing genetic diversity needs to be assessed for conservation. The current study assessed the genetic variation of Napier grass collections from selected regions in Eastern Africa and the International Livestock Research Institute Forage Germplasm- Ethiopia. The diversity of 281 cultivars was investigated using five selective amplified fragment length polymorphism (AFLP) markers and classical population genetic parameters analysed using various software. The number of bands generated was 216 with fragments per primer set ranging from 50 to 115. Mean percentage polymorphic loci was 63.40. Genetic diversity coefficients based on Nei's genetic diversity ranged from 0.0783 to 0.2142 and Shannon's information index ranged from 0.1293 to 0.3445. The Fst value obtained was moderately significant (Fst 0.1688). Neighbour-joining analysis gave two distinct clusters which did not reflect geographical locations. Analysis of molecular variance showed all variance components to be highly significant (P , 0.001), indicating more variation within (91 %) than between populations (9 %). Results suggested moderate genetic differentiation among Napier grass populations sampled, which could imply a high germplasm exchange within the region. The AFLP markers used in this study efficiently discriminate among cultivars and could be useful in identification and germplasm conservation. © The Authors 2013. Source


Rashid K.,Egerton University | Rashid K.,Tea Research Foundation of Kenya | Wachira F.N.,Tea Research Foundation of Kenya | Wachira F.N.,Association for Strengthening Agricultural Research in Eastern and Central Africa | And 5 more authors.
Nutritional Neuroscience | Year: 2014

Studies on antioxidants as neuroprotective agents have been hampered by the impermeability of the blood brain barrier (BBB) to many compounds. However, previous studies have shown that a group of tea flavonoids, the catechins, are brain permeable and neuroprotective. Despite this remarkable observation, there exist no data on the bioavailability and pharmacological benefits of tea anthocyanins (ACNs) in the brain tissue. This study investigated the ability of Kenyan purple tea ACNs to cross the BBB and boost the brain antioxidant capacity. Mice were orally administered with purified and characterized Kenyan purple tea ACNs or a combination of Kenyan purple tea ACNs and coenzyme- Q10 at a dose of 200 mg/kg body weight in an experiment that lasted for 15 days. Twenty-four hours post the last dosage of antioxidants, CO2 was used to euthanize the mice after which the brain was excised and used for various biochemical analyses. Brain extracts were analysed by high-performance liquid chromatography for ACN metabolites and spectrophotometry for cellular glutathione (GSH). Kenyan purple tea ACNs significantly (P < 0.05) raised brain GSH levels implying boost in brain antioxidant capacity. However, co-administration of both antioxidants caused a reduction of these beneficial effects implying a negative interaction. Notably, ACN metabolites were detected in brain tissue of ACN-fed mice. Our results constitute the first demonstration that Kenyan purple tea ACNs can cross the BBB reinforcing the brain's antioxidant capacity. Hence, the need to study them as suitable candidates for dietary supplements that could support antioxidant capacity in the brain and have potential to provide neuroprotection in neurodegenerative conditions. © W. S. Maney & Son Ltd 2014. Source


Benin S.,International Food Policy Research Institute | Nkonya E.,International Food Policy Research Institute | Okecho G.,National Agricultural Advisory Services Secretariat | Randriamamonjy J.,International Food Policy Research Institute | And 3 more authors.
Agricultural Economics | Year: 2011

The aim of this paper is to assess the direct and indirect impacts of the agricultural extension system of Uganda, the National Agricultural Advisory Services (NAADS) program, on household agricultural income. Data from two rounds of surveys of Ugandan rural farm-households conducted in 2004 and 2007, as well as different program evaluation methods and model specifications, are used to estimate impacts and compute a rate of return. The direct and indirect impact of the program is estimated at 37-95% and 27-55% increase in per capita agricultural gross revenue between 2004 and 2007 for households participating directly and indirectly in the program, respectively, compared to nonparticipants. The rate of return on the program's expenditures is estimated at 8-49%. The program has been relatively more effective among male-headed, larger, and asset-poor households, as well as those taking up noncrop high-value enterprises and living further away from financial services, all-weather roads, and markets or located in the Eastern and Northern Regions. Policy implications of the results are drawn. © 2010 International Association of Agricultural Economists. Source

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