Abstract
Cape St. Paul Wilt Disease (CSPWD) is a major factor that impacts on coconut productivity in Ghana. Novel markers that might be specific for a promising variety of coconut or that could validate the efficacy of crosses would be valuable for confidence in the identity of palms. This study couples the discovery of such a marker with a high throughput genotyping system based on high resolution melt curve analysis. Using oligonucleotides designed against kinase subdomains of receptor like kinases (RLKs) of other plant species, eight putative RLK genes were isolated from coconut, and the intron sequence of one of these analysed in more detail. Three single nucleotide polymorphisms (SNPs) were identified within this intron that could be used as a tractable marker to differentiate two distinct genotypes, and which could be differentiated using high resolution melt curve analysis. Analysis of different varieties of coconut used in the breeding programme included promising hybrids such as Sri Lanka Green Dwarf x Vanuatu Tall. F1 crosses between these palms had been self pollinated to generate F2 populations. Genotyping of palms at the RLK marker suggested that some F2 offspring of parent F1 palms may have been sired via cross pollination from neighbouring palms, a possibility that would bear significance for such breeding programmes. Key words: Coconut, genetic markers, receptor-like kinases, high resolution melt curve analysis, single nucleotide polymorphisms (SNPs). 
Highlights
Coconut (Cocos nucifera L.; Arecaeae) is an important crop in coastal tropical areas where it supports the livelihoods of many poor people and helps sustain the environment
Oligonucleotides RLKF/RLKR were used to obtain putative receptor like kinases (RLKs) sequences from DNA extracted from four varieties of coconut (MYD, Sri Lanka Green Dwarf (SGD), Vanuatu tall (VTT) and West Africa tall (WAT))
From the cloned sequences analysed, sequences for eight putative unique RLKs were obtained that, upon translated Basic Local Alignment Search Tool (BLAST) searching of protein sequences in National Center for Biotechnology Information (NCBI), were found to have highly significant homology with RLK protein sequences from species including tomato, vine, Arabidopsis thaliana, maize and castor oil plant, Ricinus communis (Table 2, Figure 1b)
Summary
Coconut (Cocos nucifera L.; Arecaeae) is an important crop in coastal tropical areas where it supports the livelihoods of many poor people and helps sustain the environment. Twelve million hectares of coconut are grown worldwide and 96% of the farmers are smallholders, tending less than four hectares (Eden-Green, 1999; Dery et al, 2005). A major factor that impacts on coconut productivity in Ghana and throughout Africa, as well as in the Caribbean and Abbreviations: LYD, Lethal yellowing disease; CSPWD, Cape St Paul wilt disease; LY, lethal yellowing; MYD, Malayan dwarf; PNT, Panama tall; VTT, Vanuatu tall; SGD, Sri Lanka Green Dwarf; SSRs, small sequence repeats; WAT, West Africa tall; CTAB, cetyl trimethyl ammonium bromide; BLAST, Basic local alignment search tool; PCR, polymerase chain reaction; NCBI, National Center for Biotechnology Information; ESTs, expressed sequence tags
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