Genetic Diversity and Relationships of Coconut (Cocos nucifera L) Revealed by Microsatellite Markers

A recent advance in the field of molecular biology has been the development and application of molecular markers in plant and animal species for establishing genetic relationships and phytogeny, accurate estimation of amount and distribution of genetic diversity, and identification of marker-trait associations/linkages useful in marker-assisted selection. Among the many molecular marker techniques available, microsatellites (Simple Sequence Repeats or SSRs) are attractive, since they are reproducible, easy to perform through PCR, highly informative, codominant, and multiallelic in nature. This chapter reviews the application of microsatellites in studying genetic diversity and relationships of coconut. Overall a very high level of genetic diversity has been found in coconut, more so in outbreeding Tall coconuts than in inbreeding Dwarf coconuts. Most genetic variation in Dwarfs was found between populations but was more or less equally distributed within and between populations in Tails. The number of alleles detected in Tails was nearly double the number of alleles detected in Dwarfs, indicating a loss of allelic richness in the latter. Genetic relationship studies revealed two major groups of genetically different Tall coconuts, one from Southeast Asia and the Pacific, 156 the other from southern Asia and Africa. Dwarfs, on the other hand, formed a genetically tight single cluster and moreover fell in with the Southeast Asia and Pacific Tall cluster. This observation and loss of allelic richness in Dwarfs tend to suggest that Dwarfs originated from Talis from Southeast Asia and the Pacific, probably as a result of domestication.