Plant & Animal Genomes XVIII Conference Plant & Animal Genomes XVIII ConferenceJanuary 9-13, 2010
Town & Country Convention Center
San Diego, CA
Two different studies were carried out to identify the genomic regions controlling several traits, including the resistance of cocoa to Phytophthora pod rot (Ppr), the major cause of yield losses in cocoa production in Cameroon.
In the first study, a population from a single farm, composed of 263 cocoa trees originated from 12 full-sib progenies was studied. These trees were analyzed using 125 SSR markers defined in expressed genes and mapped along the ten cocoa chromosomes. The number of sub-populations generated and the percentage of admixture of each tree was determined. Association mapping was performed between phenotypes and genotypes, taking into account the admixture percentages, in order to identify molecular markers linked to tolerance to Ppr and a few other agronomic traits. Several significant associations between molecular markers and these traits were identified, some of them matching with the position of QTLs (quantitative trait loci) identified in previous analyses.
In the second study, the objective was to validate the presence of favourable QTL alleles for Ppr resistance (identified in QTL studies), on a population of 300 trees collected in several cocoa farms. These trees were fingerprinted using 40 microsatellite markers closely linked to QTLs of the Ppr resistance. All the data generated from the fingerprinting were analysed to determine genetic structure of the population. The phenotypic data previously collected (resistance to Ppr by leaf and pod tests) were correlated to the information generated with microsatellites, in order to validate the presence of favourable Phytophthora resistant genes. The presence of resistance QTLs will be used in the MAS for Ppr.
Keywords : Cocoa; Phytophthora pod rot, Marker assisted selection, association mapping