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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF AN INTERNATIONAL MARKER ASSISTED SELECTION PROGRAM FOR CACAO Title: Identification of marker-trait associations for self-compatibility in a segregating mapping population of Theobroma cacao L

Authors
item Royaert, Stefan
item Phillips-Mora, Wilbert -
item Arciniegas Leal, Adriana -
item Cariaga, Kathleen
item Brown, J -
item Kuhn, David
item Schnell Ii, Raymond
item Motamayor, Juan -

Submitted to: Tree Genetics and Genomes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 16, 2011
Publication Date: July 6, 2011
Citation: Royaert, S.E., Phillips-Mora, W., Arciniegas Leal, A.M., Cariaga, K.A., Brown, J.S., Kuhn, D.N., Schnell Ii, R.J., Motamayor, J. 2011. Identification of marker-trait associations for self-compatibility in a segregating mapping population of Theobroma cacao L. Tree Genetics and Genomes. DOI 10.1007/s11295-011-0403-5.

Interpretive Summary: Theobroma cacao L. (cacao) is grown commercially for its beans, which are used in the production of cocoa butter and chocolate. We are striving to identify and evaluate better molecular genetic markers that are linked to important economic traits to aid marker assisted selection (MAS) breeding programs for cacao, to ensure a reliable supply of cocoa for the US confectionary industry. Self-incompatibility (SI, prevention of self-fertilization) often restricts progress, as crosses between certain cacao germplasm accessions and breeding lines are only partially successful. Genes regulating SI in cacao have not been previously located, and therefore, knowledge of the location of those genes will be very useful for the selection of uniformly self-compatible cultivars. We studied SI in a mapping population originating from a cross between a self-incompatible clone, Pound-7, and a self-compatible clone, UF-273. Important differences between flower retention at 15, 21 and 28 days after self-pollination were observed. The results obtained in this study on the parents and the mapping population suggest that the best time to measure flower retention is later than 15 days after pollination, and that selecting thresholds of flower retention for SI is genotype-specific. One microsatellite marker, mTcCIR222, was strongly associated with self-incompatibility, as well as three surrounding markers (mTcCIR168, mTcCIR115 and mTcCIR158). They were all located near the proximal end of linkage group 4. The markers are currently being tested for selecting self-incompatibility in our marker-assisted selection program. This should allow the cacao scientific community to make faster progress in breeding and to prepare for future challenges to continue to increase yield, and to improve quality and disease resistance.

Technical Abstract: Increasing yield, quality and disease resistance are important objectives for cacao breeding programs. However, self-incompatibility (SI) often restricts progress, as crosses between certain cacao germplasm accessions and breeding lines are only partially successful. Genes regulating SI in cacao have not been previously located. Knowledge of the location of the genes and the effects of alleles determining SI will be very useful for the selection of uniformly self-compatible cultivars. We studied SI in a mapping population originating from a cross between a self-incompatible clone, Pound-7, and a self-compatible clone, UF-273. Important differences between the percentage of flower retention at 15, 21 and 28 days after pollination were observed. In many breeding programs a single SI threshold at 15 days after pollination is used. The results obtained in this study on the parents and the mapping population suggest that the best time to measure flower retention is later than 15 days after pollination and that selecting thresholds for SI is genotype-specific. Marker-trait association analysis identified one marker, mTcCIR222, which was strongly associated with self-incompatibility, as well as three surrounding markers (mTcCIR168, mTcCIR115 and mTcCIR158) and located near the proximal end of linkage group 4. The markers are currently being tested for selecting self-incompatibility in our marker-assisted selection program.

Last Modified: 11/26/2014
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