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ARS Home » Southeast Area » Miami, Florida » Subtropical Horticulture Research » Research » Publications at this Location » Publication #141363
Title: ISOLATION, CHARACTERIZATION AND DEVELOPMENT OF WRKY GENES AS USEFUL GENETIC MARKERS IN THEOBROMA CACAO

Author
item BORRONE, J - FLORIDA INTL UNIV
item Schnell Ii, Raymond
item KUHN, D - FLORIDA INTL UNIV

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2004
Publication Date: 4/29/2004
Citation: Borrone, J.W., Schnell II, R.J., Kuhn, D.N. 2004. Isolation, characterization and development of WRKY genes as useful genetic markers in Theobroma cacao. Theoretical and Applied Genetics. 1090: 495-507.

Interpretive Summary: Many genes in plants are known from the whole genome sequencing projects using Arabidopsis and rice. Using sequences from known genes primers can be designed that allow the amplification of similar genes in other species. This approach is called a Candidate Gene Approach (CGA). Using a CGA we have isolated and characterized 16 WRKY genes from Theobroma cacao, the plant whose seed chocolate is made from. WRKY genes are involved with disease resistance in other plants and this is most likely the case in cacao. Four of these were variable in a population segregating for resistance to the witches' broom disease and were placed on the genetic linkage map for that population. These markers will be useful in selecting disease resistant individuals from populations segregating for resistance to this and other cacao diseases.

Technical Abstract: Currently, there is an international effort in improving disease resistance and crop yield in Theobroma cacao L., an economically important crop of the tropics. Molecular genetic markers are powerful tools in selective breeding of crops. The "candidate gene" approach identifies genes that may be involved a desired phenotype, and investigates their usefulness as molecular markers within a population segregating for this phenotype. We are developing molecular genetic makers in T. cacao L. using a candidate gene approach focusing upon genes involved in disease resistance. One such family is WRKY proteins, transcriptional factors associated with regulating defense responses in plants. Degenerate primers were designed to the conserved DNA-binding found in WRKY genes. One pair of degenerate primers amplified 16 unique sequences identified as WRKY gene fragments from T. cacao. Four of these sequences were polymorphic by single strand conformational polymorphism-capillary electrophoresis (SSCP-CE), and were mapped within an F2 population of T. cacao segregating for disease resistance to witches' broom disease caused by Crinipellis perniciosa. This demonstrates a simple method for isolation of individual members of a gene family, and developing them into useful genetic markers. This is the first report of a pair degenerate primers designed to amplify WRKY gene fragments directly from genomic DNA.