Genetic variation in coffee accessions in kenya and gene introgression from robusta to arabica using simple sequence repeats and random amplified polymorphic DNA
Omingo, Daniel Omari
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Coffee is rated the second most important commodity in global trade after petroleum products. It is grown in over 80 countries contributing substantially to their national economies. Although the genus Coffea is reported to comprise over 100 species, only two species (Coffea arabica L. popularly called as Arabica coffee and C Canephora.p known as Robusta) are under commercial cultivation. French Missionaries introduced coffee into Kenya around 1900 AD. Through variety improvement, some of the recommended cultivars or commercialy cultivated cultivars include K7, Batian, SL 28, Ruiru 11 and SL 34. Other coffee accessions from Ethiopia, Sudan, Kenya, Tanzania, Angola, India, Reunion, Portugal, South and Central America are conserved ex-situ at Coffee Research Station (CRS) Ruiru in germplasm fields plots. In spite of its significance, this collection of coffee has not been evaluated for genetic variability mainly at DNA level. Some of these conserved genotypes have been used as progenitors in the Coffee variety development at Coffee Research Station. In this study DNA markers Simple sequense repeats (SSR) and Randomly amplified polymorphic DNA ( RAPD) will be used to assess the genetic variation within and between species of coffee and to determine the most informative molecular marker system (SSR, RAPD) for detecting genetic variation between closely related coffee species used in this study ,will also be used to test the hypothesis of gene introgression from Ccanephora into Carabica . These molecular marker techniques are quite informative and have many merits such as: not subjected to environmental factors and growth stage of the plant, the potential of their existing in unlimited numbers and covering the entire genomes. A total of 24 coffee genotypes consisting of Carabica, Ceugeniodes, Ccanephora and the advanced selection will be evaluated in this study. The SSR and RAPD amplified bands will be scored for the presence (1) or absence (0) of amplified products to create a binary matrix. The total number of bands, the distribution of bands across all species, polymorphic bands, species-specific bands and average number bands per primer will be recorded .Genetic variation will be estimated using XLSTAT 2013. Genome introgression from Robusta into arabica will be analyzed by by estimating the percentage of shared bands between Robusta and Typica then the percentage of replica shared bands in arabica.The most infrornative marker will be evaluated by calculating the amount of percentage of polymorphism revealed by each marker. The result of this study will provide information which will be useful in understanding the genetic relationship between coffee species which is important for the genetic improvement and germplasm conservation.