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Duris D.,CIRAD - Agricultural Research for Development | Mburu J.K.,Coffee Research Foundation | Durand N.,CIRAD - Agricultural Research for Development | Clarke R.,FAO | And 2 more authors.
Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment | Year: 2010

This study set out to assess the relative importance of sound and unsound beans in a batch of coffee with regard to ochratoxin A (OTA) contamination. Initially, unsound beans were found to account for 95% of contamination in a batch of coffee, whatever the methods used for post-harvest processing. It was also found that beans displaying traces of attacks by Colletotrichum kahawae were the greatest contributors to OTA contamination. In a second stage, the study compared the contamination of sound beans with that of beans attacked by Colletotrichum kahawae. On average, beans attacked by Colletotrichum kahawae had a statistically higher OTA content than sound beans (18.0 μg kg-1 as opposed to 1.2 μg kg-1). In addition, the average OTA content in unsound beans varied depending on growing conditions. © 2010 Taylor & Francis. Source

Silva D.N.,Institute Investigacao Cientifica Tropical | Silva D.N.,University of Lisbon | Talhinhas P.,Institute Investigacao Cientifica Tropical | Cai L.,CAS Institute of Microbiology | And 6 more authors.
Molecular Ecology | Year: 2012

Ecological speciation through host-shift has been proposed as a major route for the appearance of novel fungal pathogens. The growing awareness of their negative impact on global economies and public health created an enormous interest in identifying the factors that are most likely to promote their emergence in nature. In this work, a combination of pathological, molecular and geographical data was used to investigate the recent emergence of the fungus Colletotrichum kahawae. C. kahawae emerged as a specialist pathogen causing coffee berry disease in Coffea arabica, owing to its unparalleled adaptation of infecting green coffee berries. Contrary to current hypotheses, our results suggest that a recent host-jump underlay the speciation of C. kahawae from a generalist group of fungi seemingly harmless to coffee berries. We posit that immigrant inviability and a predominantly asexual behaviour could have been instrumental in driving speciation by creating pleiotropic interactions between local adaptation and reproductive patterns. Moreover, we estimate that C. kahawae began its diversification at <2200 bp leaving a very short time frame since the divergence from its sibling lineage (c. 5600 bp), during which a severe drop in C. kahawae's effective population size occurred. This further supports a scenario of recent introduction and subsequent adaptation to C. arabica. Phylogeographical data revealed low levels of genetic polymorphism but provided the first geographically consistent population structure of C. kahawae, inferring the Angolan population as the most ancestral and the East African populations as the most recently derived. Altogether, these results highlight the significant role of host specialization and asexuality in the emergence of fungal pathogens through ecological speciation. © 2012 Blackwell Publishing Ltd. Source

Wagura A.G.,National Museums of Kenya | Wagai S.O.,Maseno University | Manguro L.,Maseno University | Gichimu B.M.,Coffee Research Foundation
Plant Pathology Journal | Year: 2011

The antibacterial effect of crude medicinal plant extracts of Ocimum gratissimum, Brassica oleracea var. botrytis and Ipomoea batatas on Ralstonia solanacearum (Smith) extracted from infected potato tubers was determined by in vitro study using ethyl acetate and methanol solvents. The extracts were used at concentrations of 0.4, 0.2, 0.1, 0.05 and 0.025 mg mL -1. It was found that all the plant extracts used at their different concentrations except methanol extracts oilpomea batatas at 0.025 mg mL -1 were effective to varying degrees in controlling the growth of bacterial colonies. The best results were observed with ethyl acetate extracts of Ipomoea batatas at concentration of 0.4 mg mL -1 giving mean inhibition zone of 4.2 mm followed by ethyl acetate extract of Brassica oleracea at concentration of 0.05 mg mL -1 that was 4.12 mm. © 2011 Asian Network for Scientific Information. Source

Mugiira R.B.,Ministry of Education science and Technology | Arama P.F.,Maseno University | Macharia J.M.,E gerton University | Gichimu B.M.,Coffee Research Foundation
International Journal of Agricultural Research | Year: 2011

This study was carried out with the broad objective of assessing the potential for control of Bacterial Blight of Coffee (BBC) using foliar fertilizer applications to Inhibit Ice Nucleation Activity (INA) of the causative agent (Pseudomonas syringae pv. garcae). Bacteria isolates from four coffee growing areas in Kenya were characterized based on visual, biochemical, physiological and pathogenicity characteristics to distinguish the pathogenic isolates of P. syringae from other phylloplane epiphytic bacteria. Isolates of bacteria from diseased coffee plants were categorised in three groups. Isolates that were pathogenic to coffee and produced typical symptoms of BBC fell under group 1 and were assumed to be of P. syringae pv. garcae. Other isolates that fell under groups 2 and 3 were considered to be saprophytic epiphytes. Four commercially available fertilizer formulations; Bayfolan™, Mboleasafi™, Farmphoska™ and Farmfoliar™ were tested on four pathogenic bacteria isolates collected from the four regions. All formulations significantly (p<0.05) reduced the number of bacterial colony forming units. Bayfolan™ treatment had the highest bacterial growth inhibition potential while Farmfoliar™ was least inhibitive. All the isolates were Ice Nucleation Active (INA+) and all the fertilizer formulations were potentially capable of suppressing the bacterial ice nucleation activity with Farmphoska™ being the most suppressive. Findings presented in this report indicate a potential for the management of BBC using foliar fertilizers to suppress the bacterial INA. © 2011 Academie Journals Inc. Source

Kathurima C.W.,Coffee Research Foundation | Kenji G.M.,Jomo Kenyatta University of Agriculture and Technology | Muhoho S.N.,Jomo Kenyatta University of Agriculture and Technology | Boulanger R.,CIRAD - Agricultural Research for Development | Davrieux F.,CIRAD - Agricultural Research for Development
Advance Journal of Food Science and Technology | Year: 2010

The objective of this study was to characterise some Ruiru 11 (R11) hybrids using sensory attributes and biochemical components combined with Principal Component (PC) analysis to discriminate the genotypes according to geographical locations where they were grown. Ten Ruiru 11 hybrids were evaluated in three locations in Kenya (Kitale, Koru and Ruiru) where trials were laid out in a randomized complete block design with each hybrid replicated three times. Seven sensory descriptors were assessed by a panel of seven judges and rated on a 10-point scale. Caffeine, chlorogenic acid, trigonelline, fat, and sucrose were evaluated by predictive models based on Near Infrared (NIR) spectroscopy and by chemometric analysis of the global NIR spectrum. Significant differences (p<0.05) in fragrance, flavor, aftertaste, acidity, body, balance and preference were observed among the hybrids. On average the hybrids CRF-41, CRF-11 and CRF-91 consistently scored highly in the sensory scale while CRF-3 and CRF-5 scored slightly lower.PC analysis on the sensory variables was unable to separate the samples according to geographical locations. Biochemical determinations revealed that Hybrids from Kitale had caffeine levels ranging between 1.52-1.61%, those from Ruiru 1.34-1.59% and in Koru 1.22-1.36%. The levels of sucrose in the hybrids in Koru ranged between 8.99-10.4%, which was less than the levels in the hybrids in Kitale (10.12-11.15%) and in Ruiru (9.91-10.91%). The levels of trigonelline and fat did not differ significantly in the hybrids grown in the three regions. PC analysis on the biochemical variables w as able to discriminate the samples according to geographical locations. © Maxwell Scientific Organization, 2010. Source

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