Time filter

Source Type

Kiarie S.M.,Egerton University | Karanja L.S.,Kenya Agricultural and Livestock Research Organization | Obonyo M.,Egerton University | Wachira F.N.,Association for Strengthening Agricultural Research in East and Central Africa ASARECA
Acta Horticulturae | Year: 2016

Sweet potato is a major source of dietary carbohydrate and a key food security crop in Kenya. Production of orange-fleshed sweetpotato (OFSP) in Kenya is constrained by sweetpotato virus diseases whose synergistic interaction between two virus families, sweetpotato feathery mottle virus (SPFMV) and sweetpotato chlorotic stunt virus (SPCSV). The absence of disease tolerant varieties contributes to yield losses of up to 98% that are currently observed. Research efforts in the past have concentrated on detection methods and epidemiological studies of viral infection. However, studies on the changes in quantitative contents of ß-carotene, dry matter, iron and zinc to virus infection in the OFSP varieties is prerequisite to development of virus tolerant varieties. For this reason the current study aimed at determining the effect and interaction of multiple virus infection with ß-carotene, iron and zinc levels in OFSP. Nitrocellulose membrane Enzyme-Linked Immunosorbent Assay was used to screen 10 viruses infecting OFSP. Reverse Transcriptase-PCR (RT-PCR) confirmed absence of SPCSV and SPFMV. Ninety virus free clones from six families were selected and planted in the field in a complete randomized design with three replicates. Natural virus transmission by vectors white flies (Bemisia tabaci) and aphids was allowed to occur. The plants were maintained until storage roots were formed. Clones with virus tolerance were selected. ß-carotene was quantified on root samples using Ultraviolet spectrophotometer. Atomic absorption spectrum was used to quantify Iron and zinc. Dry matter was analysed using American Association of Cereal Chemists (AACC) method. Analysis of variance (ANOVA) for effect of virus infection on ß- carotene, iron and zinc levels showed that there were no significant differences (P<0.05) among all the means on the clones used. Data was analyzed by using ANOVA (SAS Inc. 2006) then separation of means using LSD. Regression analysis revealed that the average virus score did not have an effect on dry matter and micronutrients. ANOVA revealed significant differences in dry matter among families (P<0.05). No significant differences were found among replicates. Among replicates and families, significant difference in iron content was identified (P<0.05). Disease severity scores and zinc levels among the test samples were not significant among replicates and families. There was significant differences in ß-carotene levels (P<0.05) in families but not in replicates. Separation of means displayed significant differences in iron, dry matter content and ß carotene levels among the test genotypes. The findings of the study will contribute and enhance the understanding of the effects of sweetpotato viruses on quality and quantity in OFSP and enable development of virus tolerant varieties with quantified qualitative attributes. © ISHS.


Tinzaara W.,Bioversity International | Karamura E.B.,Bioversity International | Blomme G.,Bioversity International | Jogo W.,Bioversity International | And 4 more authors.
Acta Horticulturae | Year: 2013

Banana is an important food and cash crop and constitutes a large proportion of the total crop production in East and Central African (ECA) countries. Banana production has been threatened by Xanthomonas wilt (BXW) disease caused by the bacterium Xanthomonas campestris pv. musacearum. Besides being a threat to food security in the region, the disease has severe economic implications, which emanate from yield losses and management costs. Without proper management, yields in affected areas are reduced to zero. Management approaches of the disease include use of cultural practices and awareness creation among the stakeholders along the banana value chain. These efforts to control the disease produced partial results, and the disease has continued to encroach into previously disease-free areas and to resurge in areas where it had been controlled. One of the major challenges to sustainable management of the disease has been poor understanding by stakeholders of the factors influencing disease spread and severity. Awareness creation among stakeholders has not been sustained due to limited technical, financial and infrastructural capacity. Incorrect application of cultural practices and lack of appropriate methods for field disinfection of tools coupled with weak institutional frameworks for enforcing byelaws and quarantine measures are key drivers to the continued presence of the disease in ECA. It should however be emphasized that no single management option is adequate to sustainably manage the disease. In this paper, we review mechanisms of disease transmission and drivers of the continued disease presence, and suggest approaches for sustainable management of BXW.


Mwakaje A.G.,University of Dar es Salaam | Manyasa E.,Kenyatta University | Wawire N.,Kenyatta University | Muchai M.,Kenya National Museum | And 4 more authors.
Journal of Environment and Development | Year: 2013

Protected areas occupy about 27% of Tanzania's land of 945,000 sq km and contribute 17.5% of its GDP. But who benefits from and pays for the cost of conservation? This study provides insights into these issues based on a survey conducted in the Serengeti ecosystem, involving 20 villages in Serengeti and Loliondo. The results show that villagers received insignificant benefits from conservation compared with the costs they are incurring. Governance of income at the village level was also a major challenge. There was a lack of capacity to handle large amounts of money and little or no planning, transparency, and accountability. It is recommended that income allocation to the communities is increased and external audits of village funds are conducted. Communities should furthermore be allowed to extract resources sustainably in protected areas. Youth should be encouraged to attend higher education and wildlife technical colleges to learn about the values of wildlife. Finally, the governance structures must be improved to make them gender equitable, participatory, transparent, and fully accountable to the communities and all citizens. © The Author(s) 2013.


Kerio L.C.,Tea Research Foundation of Kenya | Wachira F.N.,Association for Strengthening Agricultural Research in East and Central Africa ASARECA | Wanyoko J.K.,Tea Research Foundation of Kenya | Rotich M.K.,Egerton University
Food Chemistry | Year: 2013

Black (aerated) and green (unaerated) tea products, processed from 10 green and 18 purple leaf coloured cultivars of Kenyan origin, and two tea products, from the Japanese cultivars, Yabukita and Yutakamidori, were assayed for total polyphenols (TP) content, individual catechin profiles and in vitro antioxidant capacity (AA). In addition, the phenolic content of the tea products was determined using the Folin-Ciocalteu phenol reagent. Catechin fractions were identified using reverse phase high performance liquid chromatography (HPLC) with a binary gradient elution system. The AA% of the tea products was determined using a 2,2′-diphenyl picrylhydrazyl (DPPH) radical assay method. The results showed that TPs, catechin profiles and antioxidant activities were significantly (p ≤ 0.05) higher in unaerated than in aerated teas. Tea products from the purple leaf coloured tea cultivars had levels of TPs, total catechin (TC) and antioxidant activities similar to those from the green leaf coloured cultivars, except for teas from the Japanese cultivars that were very low in the assayed parameters. Caffeine content was significantly (p ≤ 0.05) lower in products from the purple leaf coloured cultivars than in those from the green leaf coloured tea cultivars. Antioxidant activity (%) was higher in tea products from the Kenyan germplasm than in those from the Japanese cultivars. Antioxidant potency of tea products was significantly (r = 0.789, p ≤ 0.01) influenced by the total anthocyanin content of the purple leaf coloured cultivars. Cyanidin-3-O-glucoside was the anthocyanin most highly correlated with AA% (r = 0.843, p ≤ 0.01 in unaerated tea). Total catechins in the unaerated products from the green leaf coloured tea cultivars were also significantly correlated with antioxidant capacity (r = 0.818 p ≤ 0.01). Results from this study suggest that the antioxidant potency of teas is dependent on the predominant flavonoid compound, the type of tea cultivar and the processing method. © 2012 Elsevier Ltd. All rights reserved.


Korir M.W.,Egerton University | Wachira F.N.,Association for Strengthening Agricultural Research in East and Central Africa ASARECA | Wanyoko J.K.,Tea Research Foundation of Kenya | Ngure R.M.,Egerton University | Khalid R.,Tea Research Foundation of Kenya
Food Chemistry | Year: 2014

Several studies have demonstrated that tea flavonoids protect cells and tissues against free radicals which have been implicated in the etiology of oxidative stress-related disease disorders. However, black tea is commonly consumed with additives that could otherwise affect the bioavailability of the active tea molecules. In this study, the biochemical parameters of Kenyan teas were determined and the effect of added milk and sweeteners on the antioxidant activity of Kenyan teas was investigated. The effect of tea antioxidants on glutathione (GSH) was also evaluated in vivo in a time series study using Swiss mice. Green teas had the highest levels of total polyphenols, total and individual catechins, while black teas had high levels of total thearubigins, total theaflavins and theaflavin fractions. The antioxidant activity was high in green teas though some of the black teas were as efficacious as the green teas. The addition of milk, sugar and honey significantly (p < 0.05) decreased the antioxidant activity of tea in a concentration-dependent manner. Addition of the sweetener, stevia (Stevia rebaudiana Bertoni), showed no significant (p > 0.05) influence on the antioxidant activity of tea and therefore can be recommended as a preferred sweetener for tea. Significantly (p < 0.001) higher levels of GSH were observed in plasma than in other tissues. GSH levels were generally highest 2 h after tea consumption, which indicates the need to repeatedly take tea every 2 h to maximise its potential health benefits. © 2013 Elsevier Ltd. All rights reserved.

Loading Association for Strengthening Agricultural Research in East and Central Africa ASARECA collaborators
Loading Association for Strengthening Agricultural Research in East and Central Africa ASARECA collaborators