Selection for resistance to black pod disease and yield gains prediction by use of selected cocoa varieties in Cameroon

Research on resistance to black pod caused by Phytophthora megakarya has been carried out in Cameroon for 40 years. It has yielded a significant database which is currently being exploited for the modelling of disease resistance levels of the major clones selected as candidate parents for the creation of new resistant and consequently more productive cocoa varieties. These outputs are expected to meet the increasing need of producers for improved planting material to extend cultivation into emerging cocoa-growing areas or to renew old cocoa production basins. These outputs have been made possible through an international collaborative effort and, more recently, within the scope of regional or international initiatives sponsored by CFC/ICCO/IPGRI and by CAOBISCO. New selection approaches and methodologies, such as rapid field assessment and early screening tests, have been promoted, along with the use of molecular tools for genome mapping and disease resistance quantitative trait locus (QTL) identification. Promising material has been introduced, evaluated in the laboratory and on-farm, and compared to the local cocoa germplasm. The basic knowledge developed from this local database has enabled the definition of an empirical disease resistance sorting and subsequently a prediction of the yield gains expected from the use of different cocoa clones and possible combinations (progenies) available on-station and in farmers' stands in different agro-ecological growing conditions; or which have to be created following strategies in the new breeding programme.