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World coconut germplasm has been classified
broadly as tall and dwarf coconuts based on palm stature.
D w arf coconuts are predominantly self-breeding purelines
hypothesised to have derived from tall coconuts. Dwarfs
are categorized as yellow, great, red and brown on the colour
o f epicaip and are important as parents in hybridization o f
coconuts for desirable traits. Sri Lankan yellow dwarfs
(SLYD) were observed to have uncommon phenotypes
which were not previously reported for dwarf coconuts in
the world, and this study was conducted to elucidate the
population structure o f SLYD. One hundred and two randomly selected SLYD individuals were categorized into three
morphological groups and their genotypes were derived at 30
SSR loci. Genotypic data were analysed in PowerMarker
3.2.5 and Structure 2 .3.4 software to derive the genetic diversity and the population structure. Unexpectedly high
numbrs o f alleles, genotypes, gene diversity and heterozygosity values were recorded for SLYD. Four populations were
identified within SLYD under admixture model and their
morphological variations were determined. Cross pollination
between the dw arf and tall coconut varieties followed by the
fixing o f alleles by subsequent self-pollination was
hypothesised to be the cause for the emergence o f new genetic groups within dwarf populations. The study demonstrated the formation o f new genotypes upon limited cross
pollination o f even naturally self-pollinating tree crops. The
information will be useful for developing strategies for germplasm conservation, practical coconut breeding and determining the domestication and evolution o f dwarf coconuts.
