Construction and characterization of a de novo draft genome of garden cress (Lepidium sativum L.).

Garden cress (Lepidium sativum L.) is a Brassicaceae crop recognized as a healthy vegetable and a medicinal plant. Lepidium is one of the largest genera in Brassicaceae, yet, the genus has not been a focus of extensive genomic research. In the present work, garden cress genome was sequenced using the long read high-fidelity sequencing technology. A de novo, draft genome assembly that spans 336.5 Mb was produced, corresponding to 88.6% of the estimated genome size and representing 90% of the evolutionarily expected orthologous gene content. Protein coding gene content was structurally predicted and functionally annotated, resulting in the identification of 25,668 putative genes. A total of 599 candidate disease resistance genes were identified by predicting resistance gene domains in gene structures, and 37 genes were detected as orthologs of heavy metal associated protein coding genes. In addition, 4289 genes were assigned as "transcription factor coding." Six different machine learning algorithms were trained and tested for their performance in classifying miRNA coding genomic sequences. Logistic regression proved the best performing trained algorithm, thus utilized for pre-miRNA coding loci identification in the assembly. Repetitive DNA analysis involved the characterization of transposable element and microsatellite contents. L. sativum chloroplast genome was also assembled and functionally annotated. Data produced in the present work is expected to constitute a foundation for genomic research in garden cress and contribute to genomics-assisted crop improvement and genome evolution studies in the Brassicaceae family.

A barcode-DNA analysis method for the identification of plant oil adulteration in milk and dairy products.

In the present work, a barcode-DNA analysis method is described for the detection of plant oil adulteration in milk and dairy products. The method relies on the fact that plant DNA should not be present in readily detectable amounts in a dairy product unless it contains undeclared plant material. Thus, a universal plant barcode is chosen as the target to be amplified from dairy samples. Accordingly, barcode PCR-CE (PCR-capillary electrophoresis) assays are described, which do not require preliminary information on the species source of the adulterant oil type. Two PCR-CE assays, one operating on the plastid trnL (UAA) intron and the other targeting its inner P6 loop in nested format, were shown to detect corn, soybean, rapeseed and sunflower oils in clarified butter, milk and yogurt. Both barcodes are robustly amplified with extremely conserved primers. While the intron provides the species discrimination ability, the P6 loop provides superior detection sensitivity.

Genome-wide SNP discovery and QTL mapping for fruit quality traits in inbred backcross lines (IBLs) of solanum pimpinellifolium using genotyping by sequencing.

BACKGROUND: Solanum pimpinellifolium has high breeding potential for fruit quality traits and has been used as a donor in tomato breeding programs. Unlocking the genetic potential of S. pimpinellifolium requires high-throughput polymorphism identification protocols for QTL mapping and introgression of favourable alleles into cultivated tomato by both positive and background selection. RESULTS: In this study we identified SNP loci using a genotyping by sequencing (GBS) approach in an IBL mapping population derived from the cross between a high yielding fresh market tomato and S. pimpinellifolium (LA1589) as the recurrent and donor parents, respectively. A total of 120,983,088 reads were generated by the Illumina HiSeq next-generation sequencing platform. From these reads 448,539 sequence tags were generated. A majority of the sequence tags (84.4%) were uniquely aligned to the tomato genome. A total of 3.125 unique SNP loci were identified as a result of tag alignment to the genome assembly and were used in QTL analysis of 11 fruit quality traits. As a result, 37 QTLs were identified. S. pimpinellifolium contributed favourable alleles for 16 QTLs (43.2%), thus confirming the high breeding potential of this wild species. CONCLUSIONS: The present work introduced a set of SNPs at sufficiently high density for QTL mapping in populations derived from S. pimpinellifolium (LA1589). Moreover, this study demonstrated the high efficiency of the GBS approach for SNP identification, genotyping and QTL mapping in an interspecific tomato population.

Barcode DNA length polymorphisms vs fatty acid profiling for adulteration detection in olive oil.

The aim of this study was to compare the performance of a DNA-barcode assay with fatty acid profile analysis to authenticate the botanical origin of olive oil. To achieve this aim, we performed a PCR-capillary electrophoresis (PCR-CE) approach on olive oil: seed oil blends using the plastid trnL (UAA) intron barcode. In parallel to genomic analysis, we subjected the samples to gas chromatography analysis of fatty acid composition. While the PCR-CE assay proved equally efficient as gas chromatography analysis in detecting adulteration with soybean, palm, rapeseed, sunflower, sesame, cottonseed and peanut oils, it was superior to the widely utilized analytical chemistry approach in revealing the adulterant species and detecting small quantities of corn and safflower oils in olive oil. Moreover, the DNA-based test correctly identified all tested olive oil: hazelnut oil blends whereas it was not feasible to detect hazelnut oil adulteration through fatty acid profile analysis. Thus, the present research has shown the feasibility of a PCR-CE barcode assay to detect adulteration in olive oil.

Authentication of Botanical Origin in Herbal Teas by Plastid Noncoding DNA Length Polymorphisms.

The aim of this study was to develop a DNA barcode assay to authenticate the botanical origin of herbal teas. To reach this aim, we tested the efficiency of a PCR-capillary electrophoresis (PCR-CE) approach on commercial herbal tea samples using two noncoding plastid barcodes, the trnL intron and the intergenic spacer between trnL and trnF. Barcode DNA length polymorphisms proved successful in authenticating the species origin of herbal teas. We verified the validity of our approach by sequencing species-specific barcode amplicons from herbal tea samples. Moreover, we displayed the utility of PCR-CE assays coupled with sequencing to identify the origin of undeclared plant material in herbal tea samples. The PCR-CE assays proposed in this work can be applied as routine tests for the verification of botanical origin in herbal teas and can be extended to authenticate all types of herbal foodstuffs.

Cultivar origin and admixture detection in Turkish olive oils by SNP-based CAPS assays.

The aim of this study was to establish a DNA-based identification key to ascertain the cultivar origin of Turkish monovarietal olive oils. To reach this aim, we sequenced short fragments from five olive genes for SNP (single nucleotide polymorphism) identification and developed CAPS (cleaved amplified polymorphic DNA) assays for SNPs that alter restriction enzyme recognition motifs. When applied on the oils of 17 olive cultivars, a maximum of five CAPS assays were necessary to discriminate the varietal origin of the samples. We also tested the efficiency and limit of our approach for detecting olive oil admixtures. As a result of the analysis, we were able to detect admixing down to a limit of 20%. The SNP-based CAPS assays developed in this work can be used for testing and verification of the authenticity of Turkish monovarietal olive oils, for olive tree certification, and in germplasm characterization and preservation studies.

A SNP-based PCR-RFLP capillary electrophoresis analysis for the identification of the varietal origin of olive oils.

Authenticity and traceability of high quality monovarietal extra virgin olive oils is a major concern for markets and consumers. Although analytical chemistry techniques are widely used to satisfy these needs recently developed DNA-based methods can serve as complementary approaches. A SNP database comprising 10 Greek olive varieties was constructed and five SNPs, residing in restriction sites, were selected for the development of a PCR-RFLP capillary electrophoresis method to discriminate these varieties using leaf DNA as template. An identification key was constructed indicating that five SNPs were adequate to discriminate nine out of the 10 varieties. As a proof of principle the assay was applied on DNA extracted from five of their corresponding monovarietal olive oils. Three SNPs were able to identify the varietal origin of these olive oils confirming the validity of this approach.