Submitted to: International Workshop on the Contribution of Disease Resistance to Cocoa
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2001
Publication Date: N/A
Interpretive Summary: Chocolate trees, the source of all chocolate, face serious insect and disease problems in the equatorial regions of the world where it is grown. Production of cocoa has declined in Brazil more than 70% in the last 15 years due to these problems. In order to breed trees with better natural resistance to these disease problems, we need more information about the genetic backgrounds of trees that have been in cultivation for up to 400 years with no records of where or how they were first collected. We have developed a system of DNA fingerprinting for these trees which is being reported in this manuscript, that will be accepted as the global standard for cocoa throughout the world. This manuscript is the result of an international conference where the protocols for providing a common global DNA fingerprint of chocolate trees were adopted by international agreement.
Technical Abstract: Living germ plasm collections of Theobroma cacao genotypes are maintained in several international collections scattered throughout Central and South America and the Caribbean Islands. The United States Department of Agriculture has begun a program to identify and describe the genetic diversity of these collections using state of the art molecular fingerprinting techniques. Two separate molecular analysis techniques, AFLP DNA analyses and SSR DNA analysis, were performed on T. cacao germ plasm to evaluate the utility of these procedures for DNA fingerprinting of this tree crop. DNA fragments were selectively amplified, labeled with fluorescent dyes, and separated by capillary electrophoresis using two different models of DNA analyzers (an ABI/Perkin Elmer 310 single capillary injector and a Beckman CEQ 2000 eight channel capillary DNA analyzer). Using either procedure, electropherograms of DNA fragment patterns were reproducible and consistent within a common genotype, while differentiating separate genotypes. Similarity dendrograms were based on the combined cluster analysis of AFLP primer sets of polymorphic peaks or from SSR primers selectively amplified with PCR technology. Based on this study, 15 primers for SSR markers have been selected as an international standard technique for T. cacao molecular characterization.