Browsing by Author "Gimase, J.M."
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Item Coffee Improvement by Interspecific Hybridization(2015) Omondi, C.O.; Gimase, J.M.; Kathurima, C.W.Considerable studies on creation of the interspecific hybrids using induced tetraploid Gaffea canephara P. and Gaffea arabica L. varieties for improvement of resistance to Coffee Berry Disease (CBD) and Goffee Leaf Rust (CLR), growth habits, fertility, yield performance, genetic diversity, biochemical attributes and beverage quality as well as similar information on their backcrosses to Arabica coffee genotypes are reviewed in this paper. Whereas the F 1 hybrids obtained by crossing induced tetraploid Robusta and Arabica coffee exhibited low fertility, backcrossing the hybrids to G. arabica parents restored the fertility to near normal levels. The yields and beverage quality of backcrosses improved to the levels of the best parents and in some cases they were even better. Of major significance was the resistance to C BD and CLR that the tetraploid Robusta was able to impart into the backcross progenies. These progenies were therefore potential substitutes for the susceptible Arabica coffee varieties in addition to taking the place of Robusta which has Inferior beverage quality.Item Genetic Characterization of Arabusta Coffee Hybrids and Their Parental Genotypes Using Molecular Markers(2014) Gichuru, E.K.; Thagana, W.M.; Gichimu, B.M.; Gimase, J.M.; Kirubi, D.T.Twenty coffee genotypes were characterized comprising of eleven F 1 interspecific Arabusta hybrids, three induced tetraploid Robusta parental genotypes, four Arabica parental genotypes, one diploid Robusta accession and one Hybrido de Timor (HDT), a natural interspecific hybrid between Arabica and Robusta. Characterization was conducted using thirteen Simple Sequence Repeats (SSR) and ten Random Amplified Polymorphic DNA (RAPD) molecular markers. The molecular data were analyzed for polymorphism and also subjected to cluster analysis using Unweighted Pair Group Method with Arithmetic Average (UPGMA) to estimate the diversity among the genotypes. SSR markers revealed a genetic diversity of 51.5%, 50% and 6.9% while RAPD markers revealed genetic diversity of 51.6%, 47.4% and 3.5% within induced tetraploid Robusta, F I interspecific Arabusta hybrids and Arabica genotypes respectively. The SSR primers separated the genotypes into 3 distinct caharacters unlike RAPDs which separated them into 7 distinct clusters. The study therefore confirmed the narrow genetic base within Arabica coffee and successfully portrayed the possibility of broadening it through interspecific hybridization. These results can be used to select parents with high combining ability in a hybridization program between Arabica and tetraploid Robusta.Item Genetic Diversity of Arabusta Coffee (Coffea Arabica L. X Coffea Canephora Pierre) and Their Parental Genotypes(Coffee Board of Kenya, 2011) Gimase, J.M.; Coffee Board of KenyaCoffee ranks second after petroleum in international trade. In Kenya, it supports over 600,000 households, contributes up tol2% of export revenue and employs 30% of the total workforce in Agriculture. Arabica (Coffea arabica L.) and Robusta (Coffea canephora Pierre) are the two species under commercial cultivation. Arabica coffee has low genetic diversity and susceptible to Coffee Berry Disease (CBD) and Coffee Leaf Rust (CLR) while Robusta Coffee has considerable diversity and tolerant to CBD and CLR. Interspecific hybrids between the two species have been utilized as sources of resistance to CBD and CLR. Induced tetraploid Robusta genotypes were introduced to Coffee Research Foundation (CRF), Kenya from Uganda and crossed with four varieties of Arabica as female parents to obtain interspecific F 1 hybrids (Arabusta) that are resistant to CBD and CLR. This study was carried out at CRF to characterize the genetic diversity of 12 interspecific F 1 Arabusta hybrids, 3 induced tetraploid Robusta, 4 Arabica varieties, Hibrido de Timor and a diploid Robusta using 13 SSR and 10 RAPD molecular markers. Bean biochemical components and beverage quality were also analyzed. RAPD and SSR PCR products were electrophoresed in 2.3% (w/v) agarose gel with Ix TBE buffer system and visualized in a UV light after staining with ethium bromide solution. The SSR and RAPD data were scored for presence (1) or absence (0) of bands, analyzed for polymorphic rate, subjected to cluster analysis using XLST A T software and a dendrogram constructed using Un-weighted Pair Group Method with Arithmetic Averages. Coffee oils were extracted by Soxhlet method while caffeine, trigonelline, chlogenic acids (CGA) and sucrose were detected by high perfonnance liquid chromatography system. Sensory analysis was carried by a panel of six judges as per the Specialty Coffee Association of America (SCAA). Biochemical and sensory data were subjected to Analysis of Variance using COSTAT software, means separated by Student- Newman - Keuls (SNK, p::S0.05) and Principle components analysis (PCA) plotted using XLSTAT software. SSR data revealed polymorphism of 51.5%, 50% and 6.9% for induced tetraploid Robusta, interspecific F 1 Arabusta hybrids and Arabica genotypes respectively. RAPD data revealed polymorphism of 51.6%, 47.4% and 3.5% for induced tetraploid Robusta, interspecific Fl Arabusta hybrids and Arabica genotypes respectively. Cluster dendrogram separated the genotypes into various group revealing variations and indicating their relatedness. Biochemical data revealed significant (p::S0.05) differences among the genotypes for Caffeine, oils and sucrose but was not significantly different for CGA and trigonelline. Sensory data revealed highly significant (p::S0.05) differences for all the attributes. All the F 1 hybrids scored above 80 points for total score, values that were similar to SL28 and SL34. This study revealed high genetic diversity and good cup quality for F 1 hybrids hence recommended for conservation, utilization in breeding programs, further study for adaptability and selection for release as coffee varieties.
