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Hainan Tall coconut (Cocos nucifera L.), which show the advantageous characteristics of high yield, hardiness, and wind resistance, is the dominant coconut population in Hainan Island, the main area of coconut production in China. An understanding of the genetic diversities and origins of the Hainan Tall population is essential to effective breeding. To achieve this aim, we used dozens of inter-simple sequence repeat molecular markers to characterize the genetic diversity among Hainan Tall and other coconut accessions outside China. Results revealed that Hainan Tall consisted of two main subgroups reflecting different geographic distributions (such as northern vs. southern parts of Hainan Island), and other accessions lacking clear location trends because of human activities. Diversity analysis revealed that the Hainan Tall population exhibits a higher genetic diversity than that of exotic populations mostly collected from Southeast Asia. The phylogenetic clustering results indicated that the Hainan Tall population is domesticated separately from (and earlier than) other coconut accessions, and the differentiation existed within the Hainan Tall population. Among other causes, this notion may explain the high diversity within the Hainan Tall population. Overall, these findings provide a preliminary scenario of the genetic diversities and origins of the Hainan Tall population. [ABSTRACT FROM AUTHOR]

Background: Cocos nucifera (coconut), a member of the Arecaceae family, is an economically important woody palm grown in tropical regions. Despite its agronomic importance, previous germplasm assessment studies have relied solely on morphological and agronomical traits. Molecular biology techniques have been scarcely used in assessment of genetic resources and for improvement of important agronomic and quality traits in Cocos nucifera, mostly due to the absence of available sequence information. Methodology/Principal Findings: To provide basic information for molecular breeding and further molecular biological analysis in Cocos nucifera, we applied RNA-seq technology and de novo assembly to gain a global overview of the Cocos nucifera transcriptome from mixed tissue samples. Using Illumina sequencing, we obtained 54.9 million short reads and conducted de novo assembly to obtain 57,304 unigenes with an average length of 752 base pairs. Sequence comparison between assembled unigenes and released cDNA sequences of Cocos nucifera and Elaeis guineensis indicated that the assembled sequences were of high quality. Approximately 99.9% of unigenes were novel compared to the released coconut EST sequences. Using BLASTX, 68.2% of unigenes were successfully annotated based on the Genbank non-redundant (Nr) protein database. The annotated unigenes were then further classified using the Gene Ontology (GO), Clusters of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Conclusions/Significance: Our study provides a large quantity of novel genetic information for Cocos nucifera. This information will act as a valuable resource for further molecular genetic studies and breeding in coconut, as well as for isolation and characterization of functional genes involved in different biochemical pathways in this important tropical crop species. [ABSTRACT FROM AUTHOR]

Elaeis guineensis is a tropical oil crop and has the highest oil yield per unit area. Palm oil has high palmitic acid content and is also rich in vitamins, including vitamin E. We conducted genome-wide association studies in a diversity panel of 161 E. guineensis accessions to identify single-nucleotide polymorphisms (SNPs) linked with vitamin E and validated candidate genes in these marker-associated intervals. Based on the SNPs reported in our previous research, 47 SNP markers were detected to be significantly associated with the variation of tocopherol and tocotrienol content at a cutoff P value of 6.3 × 10 -7 . A total of 656 candidate genes in the flanking regions of the 47 SNPs were identified, followed by pathway enrichment analysis. Of these candidate genes, EgHGGT (homogentisate geranylgeranyl transferase) involved in the biosynthesis of tocotrienols had a higher expression level in the mesocarp compared to other tissues. Expression of the EgHGGT gene was positively correlated with the variation in α-tocotrienol content. Induced overexpression of the gene in Arabidopsis caused a significant increase in vitamin E content and production of α-tocotrienols compared to wild Arabidopsis .