RAPD Analysis of South Pacific Coconut Palm Populations

Abstract

The South Pacific region represents a large potential genetic resource for improvement of coconut palms (Cocos nucifera L.). A study of the genetic diversity in the species was made in 1992–1993 by means of RAPD analysis on a representative sample from 17 distinct South Pacific coconut populations to characterize the germplasm present in the region. A moderate level of genetic diversity was found, although very few RAPD markers were unique to specific populations. Approximately 60% of the observed diversity occurred within‐populations, but this level varied between the various populations. This indicated the generally low but variable influence of gene migration between populations, the establishment of populations by few individuals that comprised a fraction of the genetic variation of their parental populations (founder effects), and subsequent selection by the local human population. Although the coconut populations of the region generally displayed a pattern of continuous variation, this continuum could be divided into discrete groups by cluster analysis. This division comprised a southern group of populations, a northern‐eastern group, and singlepopulation groups from the Marquesas and Hawaii groups. The population from Rennell Island diverged from the main genetic continuum, apparently because of isolation and artificial selection. Collection and conservation strategies have been devised for coconut germplasm in the South Pacific region based on existing genetic diversity.

Analysis of coconut (Cocos nucifera L.) diversity using microsatellite markers with emphasis on management and utilisation of genetic resources

“…The origin and dispersal of coconut was long debated until recent DNA analyses provided substantial evidence for its origin as the atolls in the far-east or Pacific [4][5][6][7][8] . Coconuts have gone through a severe selection process assisted by man for over many generations for traits such as nut yield, fruit constituents, quantity and quality of oil.…”

“…It is believed that the 'dwarf' originated from earliest 'tall' coconuts in atolls of the far east and maintained most of its original genome because of its autogamous behaviour [6][7][8] . Thus, dwarf coconuts are of similar stature and fruit features irrespective of the geographical location.…”

“…Characterization and evaluation of coconut germplasm by morphological descriptors alone have failed to elucidate an accurate picture of true genetic variation because of time, land and cost constraints for carrying out controlled evaluation experiments. Earlier attempts made however, have shown a few inflorescence descriptors and fruit components as useful descriptors in assessing coconut germplasm 6 . Efforts made to reveal coconut genetic diversity by isozyme analysis too had met with meagre success, mainly due to technical limitations 9,10 .…”

“…This method was successfully used as a multiplex system for assessment of coconut genetic diversity and lately, in constructing a preliminary linkage map of coconut 13,14 . There were a number of successful studies using randomly amplified polymorphic DNA (RAPDs) 6,15,16 , restriction fragment length polymorphisms (RFLPs) 7 , amplified fragment length polymorphisms (AFLPs) 7 and microsatellite polymorphisms (SSRs) 8,18,[19][20][21] that led to the understanding of the genetic diversity of coconut world over and its dissemination. Genetical relationship of coconut germplasm in Sri Lanka has so far not been assessed on a wider scale despite a few studies made on small samples of morphologically distinctive coconut groups 15,17,19 .…”

Characterization of Annur and Bedakam Ecotypes of Coconut from Kerala State, India, Using Microsatellite Markers

“…There are different techniques available to assess genetic diversity. Among these, molecular markers have the potential to significantly increase the efficiency of coconut genetic improvement, specifically in the areas of germplasm management, genotype identification, and marker-assisted selection of economically important traits [15]. Microsatellites or simple sequence repeats (SSRs) are tandemly repeated motifs of 1-6 bases found in all prokaryotic and eukaryotic genomes analyzed to date.…”