IDENTIFICATION OF RAPD MARKERS FOR RESISTANCE TO COFFEE BERRY DISEASE, COLLETOTRICHUM-KAHAWAE, IN ARABICA COFFEE

Resistance to Coffee Berry Disease (CBD) in Arabica coffee is controll ed by at least three genes which are present in the varieties Hibrido de Timer (T gene), Catimor (T gene), Rume Sudan (R and k genes) and K7 (k gene). Hibrido de Timer, Catimor and Rume Sudan are genetically di stant from most of the commercial cultivars, and the utilisation of mo lecular markers would greatly improve the efficiency of breeding progr ammes concerned with CBD resistance. The objectives of the present wor k were therefore: (1) to identify random amplified polymorphic DNA (RA PD) markers associated with CBD resistance and (2) to identify markers which could be used to select against the genetic background of the r esistance donors. Identification of RAPD markers was carried out in th ree steps. The first step involved the comparison of the RAPD profiles between the susceptible cultivars and the resistant donors. This was followed by comparison of the RAPD profiles between resistant and susc eptible types of each donor variety. The final step involved assay of the resistance markers in the first and the second backcrosses between these donors and the recurrent parent. High genetic variability was d emonstrated in Catimor, and to some extent in Rume Sudan. Three RAPD m arkers were shown to be closely associated to the T gene. Attempts to identify markers associated with the R and k genes were less rewarding . The implications of the current observations in relation to breeding for CBD resistance in Arabica coffee are discussed.