Genetic Diversity of Arabusta Coffee (Coffea arabica L. x Coffea canephora Pierre) and their Parental Genotypes
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Date
2014-08-22
Authors
Gimase, James Mwita
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Abstract
Coffee ranks second after petroleum in international trade. In Kenya, it supports
over 600,000 households, contributes up to12% 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 1x 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 XLSTAT 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
performance 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≤0.05)
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 F1 Arabusta hybrids and Arabica genotypes respectively.
RAPD data revealed polymorphism of 51.6%, 47.4% and 3.5% for induced
tetraploid Robusta, interspecific F1 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≤0.05) differences among the genotypes for Caffeine, oils and
sucrose but was not significantly different for CGA and trigonelline. Sensory data
revealed highly significant (p≤0.05) differences for all the attributes. All the F1
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.
Description
Department of Agricultural Sciences and Technology, 161p. 2014, SB 123 .G5