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Oil palm is continually being improved via controlled crossing of selected palms to ensure sustainable yields and productivity. As such, correct parental assignment is important as the presence of illegitimates will compromise the progress of improvement. In the present study, we determined the optimal number of microsatellite (SSR) markers for detection of illegitimates in selected oil palm crosses with high confidence. Determining the optimal number of markers to assign parentage will ensure that the DNA fingerprinting will be cost effective for routine use as a quality control tool in oil palm improvement programs. Here, we evaluated a wide range of crosses that included a cross derived from wild germplasm palm. The results revealed that markers with high PIC are informative and detect most of the alleles present in a cross, including those exhibited by the illegitimates. A larger number of optimum sets of markers are needed to detect all illegitimates for crosses with higher levels of genetic diversity. The optimal number of polymorphic SSR markers determined in the present study can ensure that appropriate quality control is implemented for oil palm improvement programs.

The high yielding tenera is the commercial oil palm planting material of choice in Southeast Asia. Notwithstanding this, there is continuous effort to further improve the yield and one way to do this is by addressing the yield components (YCs). Using 4451 SNP and over 600 SSR markers, this study revealed quantitative trait loci (QTL) associated with YCs in two breeding populations, a Deli dura × Yangambi pisifera (P2) and a Deli dura × AVROS pisifera (KULIM DxP). Thirteen and 29 QTLs were identified in P2 and KULIM DxP, respectively. They were compared to other YC-linked QTLs reported previously for different genetic backgrounds by mapping the QTL-linked markers to the oil palm genome. The comparison revealed four common chromosomes containing QTLs influencing various YCs. The results reveal the possible presence of closely linked loci or pleiotropic genes influencing YCs in oil palm. Exploiting the genome data has also facilitated the discovery of candidate genes within or near the QTL regions including those related to glycosylation, fatty acid and oil biosynthesis, and development of flower, seed and fruit.

The present study evaluated an interspecific backcross two (BC2) population of oil palm, which was segregating for fatty acid composition (FAC). The purpose of this study was to construct a high-density genetic map for the population, which could be used to anchor the Elaeis guineensis (EG5) and E. oleifera (O7) genome builds and determine the physical positions of the quantitative trait loci (QTLs) associated with FAC. A high-density SNP-based and SSR-based linkage map was successfully constructed for an E. guineensis × E. oleifera BC2 population. The genetic map had 16 linkage groups spanning 1618.4 cM with 1252 markers (1152 SNPs and 100 SSRs). The physical location of the markers were determined through sequence similarity search against EG5 and O7. The majority of markers (81.2%) showed map order consistent with their corresponding position on EG5. In total, 1218 markers were also anchored to 683 scaffolds in O7. This study for the first time compared the genetic map of the BC2 population with that of a published E. oleifera × E. guineensis (O×G) interspecific F1 hybrid, which revealed 433 common markers (34.6%). More importantly marker order was generally consistent in both maps. The published EG5 facilitated orientating the mapped markers in the present BC2 map as well as in the O7 scaffolds. Major QTLs associated with iodine value (IV) and palmitic acid (C16:0) content, localized on chromosome 3 and linoleic acid (C18:2) content localized on chromosome 2 of EG5 were also for the first time positioned on the O7 build, revealing the corresponding position in the E. oleifera genome likely influencing FAC in hybrids and backcrosses.

Main conclusion: Karyotyping using high-density genome-wide SNP markers identified various chromosomal aberrations in oil palm (Elaeis guineensis Jacq.) with supporting evidence from the 2C DNA content measurements (determined using FCM) and chromosome counts. Abstract: Oil palm produces a quarter of the world’s total vegetable oil. In line with its global importance, an initiative to sequence the oil palm genome was carried out successfully, producing huge amounts of sequence information, allowing SNP discovery. High-capacity SNP genotyping platforms have been widely used for marker–trait association studies in oil palm. Besides genotyping, a SNP array is also an attractive tool for understanding aberrations in chromosome inheritance. Exploiting this, the present study utilized chromosome-wide SNP allelic distributions to determine the ploidy composition of over 1,000 oil palms from a commercial F1 family, including 197 derived from twin-embryo seeds. Our method consisted of an inspection of the allelic intensity ratio using SNP markers. For palms with a shifted or abnormal distribution ratio, the SNP allelic frequencies were plotted along the pseudo-chromosomes. This method proved to be efficient in identifying whole genome duplication (triploids) and aneuploidy. We also detected several loss of heterozygosity regions which may indicate small chromosomal deletions and/or inheritance of identical by descent regions from both parents. The SNP analysis was validated by flow cytometry and chromosome counts. The triploids were all derived from twin-embryo seeds. This is the first report on the efficiency and reliability of SNP array data for karyotyping oil palm chromosomes, as an alternative to the conventional cytogenetic technique. Information on the ploidy composition and chromosomal structural variation can help to better understand the genetic makeup of samples and lead to a more robust interpretation of the genomic data in marker–trait association analyses.

Molecular marker advancement and utilization to exploit and identify genetic diversity are the most key developments in molecular genetic studies. Molecular markers are the most common tool for exploring plant genetic diversity and area pre- requisite for gene mapping, segregation and genetic analysis, forensic assessment, phylogenetic analysis, and the achievement of many other biological goals. Despite the development of several molecular marker types that are regularly applied in plant breeding, majority of these markers are confined in their functions due to their limited accessibility and the cost of analyses carried out on a large scale. However, the advent of sequencing technologies, including next-generation sequencing (NGS) and genotyping by sequencing (GBS), has transformed plant breeding via SSR and SNP development. To date, different types of sequencing technologies have been generated and reviewed. This chapter provides insight into the spectrum of molecular marker-based detection methods and their role in determining the genetic diversity of oil palms based on sequencing.

Background The Elaeis oleifera genetic materials were assembled from its center of diversity in South and Central America. These materials are currently being preserved in Malaysia as ex situ living collections. Maintaining such collections is expensive and requires sizable land. Information on the genetic diversity of these collections can help achieve efficient conservation via maintenance of core collection. For this purpose, we have applied fourteen unlinked microsatellite markers to evaluate 532 E. oleifera palms representing 19 populations distributed across Honduras, Costa Rica, Panama and Colombia. Results In general, the genetic diversity decreased from Costa Rica towards the north (Honduras) and south-east (Colombia). Principle coordinate analysis (PCoA) showed a single cluster indicating low divergence among palms. The phylogenetic tree and STRUCTURE analysis revealed clusters based on country of origin, indicating considerable gene flow among populations within countries. Based on the values of the genetic diversity parameters, some genetically diverse populations could be identified. Further, a total of 34 individual palms that collectively captured maximum allelic diversity with reduced redundancy were also identified. High pairwise genetic differentiation (Fst > 0.250) among populations was evident, particularly between the Colombian populations and those from Honduras, Panama and Costa Rica. Crossing selected palms from highly differentiated populations could generate off-springs that retain more genetic diversity. Conclusion The results attained are useful for selecting palms and populations for core collection. The selected materials can also be included into crossing scheme to generate offsprings that capture greater genetic diversity for selection gain in the future. Electronic supplementary material The online version of this article (doi:10.1186/s12863-017-0505-7) contains supplementary material, which is available to authorized users.

Oil palm breeding involves crossing dura and pisifera palms to produce tenera progeny with greatly improved oil yield. Oil yield is controlled by variant alleles of a type II MADS-box gene, SHELL, that impact the presence and thickness of the endocarp, or shell, surrounding the fruit kernel. We identified six novel SHELL alleles in noncommercial African germplasm populations from the Malaysian Palm Oil Board. These populations provide extensive diversity to harness genetic, mechanistic and phenotypic variation associated with oil yield in a globally critical crop. We investigated phenotypes in heteroallelic combinations, as well as SHELL heterodimerization and subcellular localization by yeast two-hybrid, bimolecular fluorescence complementation and gene expression analyses. Four novel SHELL alleles were associated with fruit form phenotype. Candidate heterodimerization partners were identified, and interactions with EgSEP3 and subcellular localization were SHELL allele-specific. Our findings reveal allele-specific mechanisms by which variant SHELL alleles impact yield, as well as speculative insights into the potential role of SHELL in single-gene oil yield heterosis. Future field trials for combinability and introgression may further optimize yield and improve sustainability.

Oil palm is continually being improved via controlled crossing of selected palms to ensure sustainable yields and productivity. As such, correct parental assignment is important as the presence of illegitimates will compromise the progress of improvement. In the present study, we determined the optimal number of microsatellite (SSR) markers for detection of illegitimates in selected oil palm crosses with high confidence. Determining the optimal number of markers to assign parentage will ensure that the DNA fingerprinting will be cost effective for routine use as a quality control tool in oil palm improvement programs. Here, we evaluated a wide range of crosses that included a cross derived from wild germplasm palm. The results revealed that markers with high PIC are informative and detect most of the alleles present in a cross, including those exhibited by the illegitimates. A larger number of optimum sets of markers are needed to detect all illegitimates for crosses with higher levels of genetic diversity. The optimal number of polymorphic SSR markers determined in the present study can ensure that appropriate quality control is implemented for oil palm improvement programs.

Existing Elaeis guineensis cultivars lack sufficient genetic diversity due to extensive breeding. Harnessing variation in wild crop relatives is necessary to expand the breadth of agronomically valuable traits. Using RAD sequencing, we examine the natural diversity of wild American oil palm populations (Elaeis oleifera), a sister species of the cultivated Elaeis guineensis oil palm. We genotyped 192 wild E. oleifera palms collected from seven Latin American countries along with four cultivated E. guineensis palms. Honduras, Costa Rica, Panama and Colombia palms are panmictic and genetically similar. Genomic patterns of diversity suggest that these populations likely originated from the Amazon Basin. Despite evidence of a genetic bottleneck and high inbreeding observed in these populations, there is considerable genetic and phenotypic variation for agronomically valuable traits. Genome-wide association revealed several candidate genes associated with fatty acid composition along with vegetative and yield-related traits. These observations provide valuable insight into the geographic distribution of diversity, phenotypic variation and its genetic architecture that will guide choices of wild genotypes for crop improvement.

Palm oil is among the most important vegetable oils, contributing to a quarter of the world’s oils and fats market. The oil palm (Elaeis guineensis Jacq.) fruitlets, which are the source of palm oil, vary from 8eight to 20 g in weight. Palm oil content in the fruitlets is approximately 45 – 50 % by weight and an increase in the percentage of mesocarp-to-fruit is likely to have a positive effect on oil yield. In this study, we report a quantitative trait loci (QTL) associated with two yield related components, namely fruit and mesocarp content in a commercial breeding population (Deli dura x Yangambi pisifera). The QTL confidence interval of about 12 cM (~6.7 Mbp) was fine-mapped with 31 markers (17 SNPs and 14 SSRs) consisting of 20 nuclear markers derived from the maternal parent, six paternal and five co-segregating markers. Interestingly, inheritance of the paternal alleles leads to a larger difference in both fruit and mesocarp weight, when comparing genotypes in the progeny palms. Candidate genes and transcription factors were mined from the QTL region by positioning markers on the oil palm EG5 genome build. Putative genes and transcription factors involved in various biological processes including flower organ development, flowering, photosynthesis, microtubule formation, nitrogen and lipid metabolism were identified within this QTL interval on pseudo-chromosome 3. This genome-based approach allowed us to identify a number of potential candidate gene markers associated with oil palm fruit and mesocarp weight which can be further evaluated for potential use in marker-assisted breeding.

Palm oil has a balanced fatty acid composition and has no trans fat. As a result, its use in food has increased as food-labeling laws have changed to specify trans fat content. Increasing oil production is the main goal in oil palm breeding. Genetic mapping and genomic studies in palm trees are necessary to understand the genetic architecture of economic traits of importance for palm oil production. To help achieve this, we sampled 422 oil palms from MPOB (Malaysian Palm Oil Board)­Angola germplasm collection and measured 13 economic traits from these palms. Multi-locus genome-wide association studies (GWAS) were conducted using least absolute shrinkage and selection operator (LASSO) and genome-wide efficient mixed model analysis. We identified 19 quantitative trait loci (QTLs) for 8 traits. Of these, four Angola-specific QTLs associated with bunch components were detected on chromosomes 4, 8, and 11. These QTLs are potentially useful for introgression of desirable genes from the Angola palms to advanced breeding populations for improvement of bunch and oil yield traits. The majority of the QTLs were detected by LASSO-A, in which the p values of individual markers were calculated based on bootstrapped standard errors. Many of the detected QTLs are nearby known QTLs detected from linkage studies reported by other research groups. We also conducted genomic selection (GS) for the 13 traits and concluded that GS can be an effective tool for oil palm breeding. This is the first GWAS and GS study conducted on oil palm germplasm from Angola, and the results can be very useful in oil palm genetic studies and breeding.

Molecular genetics is essentially the study of the mechanisms and effects of trait inheritance at the molecular level. Cytogenetic analysis—the study of the numbers, structure, and organization of the chromosomes packaging the DNA within the cell nucleus—is important for understanding evolution, genetics, epigenetics, genetic recombination, and nuclear stability in all species. Oil palm is a perennial species mostly grown as a source of vegetable oil, although more recently it is also gaining popularity as a biofuel feedstock. Oil palm breeding programs were first initiated in Africa with the objective to obtain high-yielding materials for commercial planting. Whole-genome sequencing is a laboratory process that can reveal the complete DNA repertoire of an organism's genome, distributed in the nucleus, mitochondria, and chloroplasts. The reference oil palm genomes and high-density OP200K genotyping array has enabled the first genome-wide association study (GWAS) of mesocarp oil content in oil palm.

Log probability data (LnP(D)) as function of k (number of clusters) from the STRUCTURE. (DOCX 2712 kb)

The current oil palm planting materials yield three times more than the figure recorded six decades ago. This was partly achieved through genetic improvement and selection procedures imposed on the oil palm breeding populations. The repeated cycles of selection applied had removed a lot of ‘unwanted’ alleles from the breeding populations. However, this might have affected the populations’ ability to withstand environmental threat and genetic gains in the future. Realizing the important role of oil palm germplasms in harmonizing these effects, several research organizations had accumulated a large number of Elaeis guineensis and Elaeis oleifera accessions from their centers of origin. These materials exhibit greater genetic diversity and can offer genes for many economically important traits valuable for future oil palm improvement. These potential germplasm materials should be strategically conserved to ensure effective and continuous accessibility, in line with the long-term breeding cycle of the oil palm. Core collection can effectively preserve the genetic diversity of the oil palm germplasms. Apart from maintaining the genetic resources in the living ex situ field plots, in vitro methods of storing genetic materials within smaller size facilities are also available. These methods offer conservation of high numbers of materials, protection from diseases and low cost of maintenance. Both, the ex situ and in vitro methods provide complementary means for effective long-term conservation of the oil palm genetic materials for posterity.

Information of country, collection sites and population size included in the study. (DOCX 16 kb)

Details of the 18 microsatellite markers used in the study. (DOCX 16 kb)

Pearsonâ s correlation coefficients for iodine value (IV) and fatty acid composition (FAC) in palm oil of BC2 (2.6-1) validation cross. (PDF 13Â kb)

Co-linearity of markers between the OxG and BC2 (2.6-1 & 2.6-5) populations as observed in six linkage groups hosting QTLs (OT1, T2, T3, OT4, OT6 and T9). (PDF 96Â kb)

Mapping candidate markers for various fatty acid related genes in the OxG linkage map. Candidate SNP markers (SNPE, in pink) for palmitoyl-ACP thioesterase (PATE/FATB), oleoyl-CoA desaturase (FAD2), linoleoyl-CoA desaturase (FAD3), enoyl-ACP reductase (ENR1) and stearoyl-ACP desaturase (SAD) mapped onto LGs OT1, T2, OT11, OT12 and T14. Candidate SSR markers (_oSSR and sPSc, in blue) also developed for ketoacyl-ACP synthase I (KASI), acetoacetyl-CoA thiolase (AACT), long chain acyl-CoA synthetase (LACS4), AP2-like ethylene-responsive TF (WRI1), 3-hydroxyisobutyryl-CoA hydrolase-like protein 3 (HIBCH), sodium/metabolite cotransporter (BASS2), PATE/FATB and SAD. (PDF 56Â kb)

Pearsonâ s correlation coefficients for iodine value (IV) and fatty acid composition (FAC) in palm oil of OxG mapping population. (PDF 13Â kb)

Pearsonâ s correlation coefficients for iodine value (IV) and fatty acid composition (FAC) in palm oil of BC2 (2.6-5) validation cross. (PDF 13Â kb)

A total of 5,521 expressed sequence tags (ESTs) from oil palm were used to search for type and frequency of simple sequence repeat (SSR) markers. Dimeric repeat motifs appeared to be the most abundant, followed by tri-nucleotide repeats. Redundancy was eliminated in the original EST set, resulting in 145 SSRs in 136 unique ESTs (114 singletons and 22 clusters). Primers were designed for 94 (69.1%) of the unique ESTs (consisting of 14 consensus and 80 singletons). Primers for 10 EST-SSRs were developed and used to evaluate the genetic diversity of 76 accessions of oil palm originating from seven countries in Africa, and the standard Deli dura population. The average number of observed and effective alleles was 2.56 and 1.84, respectively. The EST-SSR markers were found to be polymorphic with a mean polymorphic information content value of 0.53. Genetic differentiation (FST) among the populations studied was 0.2492 indicating high level of genetic divergence. Moreover, the UPGMA (unweighted pair-group method with arithmetic mean) analysis revealed a strong association between genetic distance and geographic location of the populations studied. The germplasm materials exhibited higher diversity than Deli dura, indicating their potential usefulness in oil palm improvement programmes. The study also revealed that the populations from Nigeria, Congo and Cameroon showed the highest diversity among the germplasm evaluated in this study. The EST-SSRs further demonstrated their worth as a new source of polymorphic markers for phylogenetic analysis, since a high percentage of the markers showed transferability across species and palm taxa.

Elaeis oleifera serves as a source of genetic foundation in oil palm improvement programme, as it possess several interesting agronomic traits such as slow growth, higher oil unsaturation and disease resistance. Malaysian Palm Oil Board (MPOB) has developed a collection of simple sequence repeats (SSRs) from Elaeis oleifera genome (E. oleifera-gSSRs). A total of 21 polymoprhic SSR markers were evaluated in the attempt to assess the population structure of E. oleifera populations. The appropriate common ancestry (K) value was determined to be seven from the likelihood scores. The profile from STRUCTURE analysis indicates considerable sharing of genetic components among E. oleifera population with an exception for Population 01 from Columbia and Population 02 from Costa Rica. The present study provides information on population structure of MPOB E. oleifera collection via model-based method for germplasm conservation and utilisation in breeding programmes.

Oil palm, a plantation crop of major economic importance in Southeast Asia, is the predominant source of edible oil worldwide. We report the identification of the VIRESCENS (VIR) gene, which controls fruit exocarp colour and is an indicator of ripeness. VIR is a R2R3-MYB transcription factor with homology to Lilium LhMYB12 and similarity to Arabidopsis PRODUCTION OF ANTHOCYANIN PIGMENT1 (PAP1). We identify five independent mutant alleles of VIR in over 400 accessions from sub-Saharan Africa that account for the dominant-negative virescens phenotype. Each mutation results in premature termination of the carboxy-terminal domain of VIR, resembling McClintock’s C1-I allele in maize. The abundance of alleles likely reflects cultural practices, by which fruits were venerated for magical and medicinal properties. The identification of VIR will allow selection of the trait at the seed or early-nursery stage, 3-6 years before fruits are produced, greatly advancing introgression into elite breeding material., Fruit colour is a trait that affects the harvesting, and therefore oil yield, of the economically important oil palm. Here, the authors identify a gene that may control fruit colour in the oil palm and suggest that selection for this gene during early development could advance the breeding potential of this important crop.

Background Oil palm is an important perennial oil crop with an extremely long selection cycle of 10 to 12 years. As such, any tool that speeds up its genetic improvement process, such as marker-assisted breeding is invaluable. Previously, genetic linkage maps based on AFLP, RFLP and SSR markers were developed and QTLs for fatty acid composition and yield components identified. High density genetic maps of crosses of different genetic backgrounds are indispensable tools for investigating oil palm genetics. They are also useful for comparative mapping analyses to identify markers closely linked to traits of interest. Results A 4.5 K customized oil palm SNP array was developed using the Illumina Infinium platform. The SNPs and 252 SSRs were genotyped on two mapping populations, an intraspecific cross with 87 palms and an interspecific cross with 108 palms. Parental maps with 16 linkage groups (LGs), were constructed for the three fruit forms of E. guineensis (dura, pisifera and tenera). Map resolution was further increased by integrating the dura and pisifera maps into an intraspecific integrated map with 1,331 markers spanning 1,867 cM. We also report the first map of a Colombian E. oleifera, comprising 10 LGs with 65 markers spanning 471 cM. Although not very dense due to the high level of homozygosity in E. oleifera, the LGs were successfully integrated with the LGs of the tenera map. Direct comparison between the parental maps identified 603 transferable markers polymorphic in at least two of the parents. Further analysis revealed a high degree of marker transferability covering 1,075 cM, between the intra- and interspecific integrated maps. The interspecific cross displayed higher segregation distortion than the intraspecific cross. However, inclusion of distorted markers in the genetic maps did not disrupt the marker order and no map expansion was observed. Conclusions The high density SNP and SSR-based genetic maps reported in this paper have greatly improved marker density and genome coverage in comparison with the first reference map based on AFLP and SSR markers. Therefore, it is foreseen that they will be more useful for fine mapping of QTLs and whole genome association mapping studies in oil palm. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-309) contains supplementary material, which is available to authorized users.

Publisher Summary Plant genomics is reversing the previous paradigm of identifying genes behind biological functions and instead focuses on finding biological functions behind genes. The oil palm belongs to the genus Elaeis, which contains two species, E. Guineensis and E. oleifera. It is regarded as the most efficient oil-bearing crop in the world compared to other crops of the same genre in terms of land use. However, the oil yield of oil palm has reached stagnation of late and there is an urgent need for improvement. Hence, this chapter discusses the current trend of leveraging genomics in the production of new and improved planting materials. The genomic platforms form the resource toward achieving the target of producing superior oil palms. As with other plant genomes, the oil palm has now been sequenced and with the plummeting price of sequencing as time goes by, more genomes will follow suit. Malaysian Palm Oil Board (MPOB) is known to have the largest oil palm germplasm collection in the world. That is an ideal source for identifying new alleles essential for breeding.

The palm family, consisting of over 2,500 species arrayed among ca. 200 genera, is the third most economically important family of plants after the grasses and legumes. Three palm species account for the large majority of the family’s economic importance: coconut (Cocos nucifera), African oil palm (Elaeis guineensis), and date palm (Phoenix dactylifera). Of the three, genomics has been least developed in the coconut, where molecular tools have largely been used to characterize germplasm, and, to a lesser extent, develop quantitative trait loci (QTL). Both date palm and oil palm have recently had their genomes sequenced. The application of genomic tools to these palm species will result in enormous advances in the genetic improvement of all three crops.

Studies were conducted to assess the genetic relationships between the parental palms (dura and pisifera) and performance of their progenies based on nine microsatellite markers and 29 quantitative traits. Correlation analyses between genetic distances and hybrids performance were estimated. The coefficients of correlation values of genetic distances with hybrid performance were non-significant, except for mean nut weight and leaf number. However, the correlation coefficient of genetic distances with these characters was low to be used as predicted value. These results indicated that genetic distances based on the microsatellite markers may not be useful for predicting hybrid performance. The genetic distance analysis using UPGMA clustering system generated 5 genetic clusters with coefficient of 1.26 based on quantitative traits of progenies. The genotypes, DP16, DP14, DP4, DP13, DP12, DP15, DP8, DP1 and DP2 belonging to distant clusters and greater genetic distances could be selected for further breeding programs.

This study reports on the detection of additional expressed sequence tags (EST) derived simple sequence repeat (SSR) markers for the oil palm. A large collection of 19243 Elaeis guineensis ESTs were assembled to give 10258 unique sequences, of which 629 ESTs were found to contain 722 SSRs with a variety of motifs. Dinucleotide repeats formed the largest group (45.6%) consisting of 66.9% AG/CT, 21.9% AT/AT, 10.9% AC/GT and 0.3% CG/CG motifs. This was followed by trinucleotide repeats, which is the second most abundant repeat types (34.5%) consisting of AAG/CTT (23.3%), AGG/CCT (13.7%), CCG/CGG (11.2%), AAT/ATT (10.8%), AGC/GCT (10.0%), ACT/AGT (8.8%), ACG/CGT (7.6%), ACC/GGT (7.2%), AAC/GTT (3.6%) and AGT/ACT (3.6%) motifs. Primer pairs were designed for 405 unique EST-SSRs and 15 of these were used to genotype 105 E. guineensis and 30 E. oleifera accessions. Fourteen SSRs were polymorphic in at least one germplasm revealing a total of 101 alleles. The high percentage (78.0%) of alleles found to be specific for either E. guineensis or E. oleifera has increased the power for discriminating the two species. The estimates of genetic differentiation detected by EST-SSRs were compared to those reported previously. The transferability across palm taxa to two Cocos nucifera and six exotic palms is also presented. The polymerase chain reaction (PCR) products of three primer-pairs detected in E. guineensis, E. oleifera, C. nucifera and Jessinia bataua were cloned and sequenced. Sequence alignments showed mutations within the SSR site and the flanking regions. Phenetic analysis based on the sequence data revealed that C. nucifera is closer to oil palm compared to J. bataua; consistent with the taxanomic classification.

Background The commercial oil palm (Elaeis guineensis Jacq.) produces a mesocarp oil (commonly called ‘palm oil’) with approximately equal proportions of saturated and unsaturated fatty acids (FAs). An increase in unsaturated FAs content or iodine value (IV) as a measure of the degree of unsaturation would help to open up new markets for the oil. One way to manipulate the fatty acid composition (FAC) in palm oil is through introgression of favourable alleles from the American oil palm, E. oleifera, which has a more unsaturated oil. Results In this study, a segregating E. oleifera x E. guineensis (OxG) hybrid population for FAC is used to identify quantitative trait loci (QTLs) linked to IV and various FAs. QTL analysis revealed 10 major and two putative QTLs for IV and six FAs, C14:0, C16:0, C16:1, C18:0, C18:1 and C18:2 distributed across six linkage groups (LGs), OT1, T2, T3, OT4, OT6 and T9. The major QTLs for IV and C16:0 on LGOT1 explained 60.0 – 69.0 % of the phenotypic trait variation and were validated in two independent BC2 populations. The genomic interval contains several key structural genes in the FA and oil biosynthesis pathways such as PATE/FATB, HIBCH, BASS2, LACS4 and DGAT1 and also a relevant transcription factor (TF), WRI1. The literature suggests that some of these genes can exhibit pleiotropic effects in the regulatory networks of these traits. Using the whole genome sequence data, markers tightly linked to the candidate genes were also developed. Clustering trait values according to the allelic forms of these candidate markers revealed significant differences in the IV and FAs of the palms in the mapping and validation crosses. Conclusions The candidate gene approach described and exploited here is useful to identify the potential causal genes linked to FAC and can be adopted for marker-assisted selection (MAS) in oil palm. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2607-4) contains supplementary material, which is available to authorized users.