GENETIC IMPROVEMENT OF THEOBROMA CACAO
Subtropical Horticulture Research
Project Number: 6038-21000-023-03
Start Date: Dec 28, 2010
End Date: Dec 28, 2015
The primary goal of this Trust Fund Cooperative Agreement No. 58-6631-1-002 (“Agreement”) project is to set out the terms and conditions of the project to develop and disseminate new productive disease resistant cultivars of cacao. To attain that goal we have developed tools and breeding enhancement techniques that efficiently facilitate recurrent genetic improvement. These tools and techniques are being implemented in the project and have been made available to international breeding programs. Research performed in genetic resource evaluation, molecular genetics, statistics, bioinformatics, plant pathology, and practical field selection are all part of a global strategy to develop superior planting material for farmers.
The project has eight (8) specific goals:
1. Fine mapping DNA based markers associated with resistance to cacao diseases and other agronomic traits through linkage mapping or genome wide association (GWAS) to obtain useful information for developing cacao breeding strategies.
2. Establish families combining traits of interest and develop a Marker Assisted Selection (MAS) program to genetically improve cacao for resistance to these diseases and to provide new cultivars with enhanced production. This objective requires cooperation with a number of national and international research organizations in Central and South America, West Africa, and South Asia. The South and Central American institutes are the Tropical Agricultural Research and Education Center (CATIE) in Turrialba, Costa Rica, and the Instituto Nacional de Investigaciones Agricolas y Pecuarias (INIAP) Estacion Experimental Pichilingue (EET Pichilingue) in Quevedo, Ecuador. Collaboration with West African institutes is through the support of the United States Agency for the Development (USAID) and the International Institute for Tropical Agriculture (IITA) in Nigeria and directly with the Cocoa Research Institute of Ghana (CRIG). In Asia our main collaborator is the Coconut and Cacao Institute (CCI) in Papua New Guinea. To ensure access to these populations, specific cooperative agreements (SCA) have been established with these institutions.
3. Develop new molecular marker methodologies for massive screening of plants and implement those methodologies in the Marker Assisted Selection process.
4. Identify genes involved with major agronomic traits and investigate the molecular basis of their expression.
5. Develop biostatistical expertise for cacao genetics for whole genome map development, identification of marker-trait associations, molecular systematic analysis, and development of a genetic relational database.
6. Apply the biostatiscal expertise developed in the analyses of segregating populations and germplasm collections existing in the above mentioned research institutes.
7. Implement evaluation of improved material in farmers’ fields.
8. To share information on genotypic identity, breeding values of the genotypes studied available through our database or the database established in collaboration with Washington State University (WSU).
Markers associated with the key agronomic traits will be used in MAS programs to select for new varieties emphasizing the resistance to the most important cacao pathogens. Candidate gene markers along with microsatellite markers were used to produce the first definitive saturated linkage map of Theobroma cacao. One major and one minor Quantitative Trait Locus (QTL) were discovered controlling resistance to witches’ broom and three QTLs have been identified for resistance to frosty pod. One QTL has also been identified regulating reproductive self-incompatibility in cacao. Assays are being developed to use these markers for selection in current breeding populations. These assays will be used to pre-select genotypes for field testing allowing greater efficiency in the identification of superior individuals. These QTLs are also being used to locate the respective genes in the cacao genome.