DEVELOPMENT OF AN INTERNATIONAL MARKER ASSISTED SELECTION PROGRAM FOR CACAO
Location: Subtropical Horticulture Research
Title: The detection and utilization of disease resistance, quality, and productivity QTLs in cacao breeding
Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: January 4, 2010
Publication Date: January 10, 2010
Citation: Schnell Ii, R.J., Brown, J.S., Tondo, C.L., Kuhn, D.N., Phillips, W., Amores, F., Takrama, J., Motamayor, J.C. 2010. The detection and utilization of disease resistance, quality, and productivity QTLs in cacao breeding. Plant and Animal Genome Conference. 1.
Over the past 15 years a number of studies have produced genetic linkage maps using a variety of molecular markers and small populations (<500 individuals), and a consensus genetic linkage map has been developed that gives the most precise estimates of marker locations and distances. QTLs have been identified for resistance to black pod (BP), frosty pod (FP), and witches' broom (WB) diseases and for 20 different growth, quality, and flavor characters. Fifteen different BP QTLs have been reported with 13 of these considered consensus QTLs; they have been mapped in more than one population. Four QTL for WB resistance and three QTL for FP have been identified each in a single population. Over 80 horticultural QTLs have been reported; however, many have been identified in only a single population and others have not been consistently detected over years. Two of the WB QTL were used to characterize seedlings of a SCA 6 x SIAL 1 cross that had been evaluated for WB in Ecuador. Seedlings homozygous for the favorable alleles at the flaking markers had a significantly reduced broom number compared to seedlings heterozygous for the favorable allele and seedlings lacking any favorable alleles were the most susceptible. In Ghana 412 seedlings from five experimental families segregating for WB and BP resistance have been characterized for WB and BP QTLs. Nine-six seedlings (23%) had the proper allelic configurations for WB resistance, 39 (9.5%) for BP resistance, and 15 (3%) for both. Disease ratings are underway, and these QTL are beginning to be used in applied cacao breeding programs.