Melon (Cucumis melo L.) is one of the most important horticultural species, which includes several taxonomic groups. With the advent of next-generation sequencing, single nucleotide polymorphism (SNP) markers are widely used in the study of genetic diversity and genomics. We report the first successful application of genotyping-by-sequencing (GBS) technology in melon. We detected 25,422 SNPs by the analysis of 72 accessions collected in Apulia, a secondary centre of diversity in Southern Italy. Analyses of genetic structure, principal components, and hierarchical clustering support the identification of three distinct subpopulations. One of them includes accessions known with the folk name of ‘carosello’, referable to the chate taxonomic group. This is one of the oldest domesticated forms of C. melo, once widespread in Europe and now exposed to the risk of genetic erosion. The second subpopulation contains landraces of ‘barattiere’, a regional vegetable production that was never characterized at the DNA level and we show was erroneously considered another form of chate melon. The third subpopulation includes genotypes of winter melon (C. melo var. inodorus). Genetic analysis within each subpopulation revealed patterns of diversity associated with fruit phenotype and geographical origin. We used SNP data to describe, for each subpopulation, the average linkage disequilibrium (LD) decay, and to highlight genomic regions possibly resulting from directional selection and associated with phenotypic variation. We used GBS to characterize patterns of genetic diversity and genomic features within C. melo. We provide useful information to preserve endangered gene pools and to guide the use of germplasm in breeding. Finally, our findings lay a foundation for molecular breeding approaches and the identification of genes underlying phenotypic traits.

Key message Overexpression of BoMYB29 gene up-regulates the aliphatic glucosinolate pathway in Brassica oleracea plants increasing the production of the anti-cancer metabolite glucoraphanin, and the toxic and pungent sinigrin. Abstract Isothiocyanates, the bio-active hydrolysis products of glucosinolates, naturally produced by several Brassicaceae species, play an important role in human health and agriculture. This study aims at correlating the content of aliphatic glucosinolates to the expression of genes involved in their synthesis in Brassica oleracea, and perform functional analysis of BoMYB29 gene. To this purpose, three genotypes were used: a sprouting broccoli, a cabbage, and a wild genotype (Winspit), a high glucosinolate containing accession. Winspit showed the highest transcript level of BoMYB28, BoMYB29 and BoAOP2 genes, and BoAOP2 expression was positively correlated with that of the two MYB genes. Further analyses of the aliphatic glucosinolates also showed a positive correlation between the expression of BoAOP2 and the production of sinigrin and gluconapin in Winspit. The Winspit BoMYB29 CDS was cloned and overexpressed in Winspit and in the DH AG1012 line. Overexpressing Winspit plants produced higher quantities of alkenyl glucosinolates, such as sinigrin. Conversely, the DH AG1012 transformants showed a higher production of methylsulphinylalkyl glucosinolates, including glucoraphanin, and, despite an up-regulation of the aliphatic glucosinolate genes, no increase in alkenyl glucosinolates. The latter may be explained by the absence of a functional AOP2 gene in DH AG1012. Nevertheless, an extract of DH AG1012 lines overexpressing BoMYB29 provided a chemoprotective effect on human colon cells. This work exemplifies how the genetic diversity of B. oleracea may be used by breeders to select for higher expression of transcription factors for glucosinolate biosynthesis to improve its natural, health-promoting properties.

Onion (Allium cepa L.) is the second most important vegetable crop worldwide and is widely appreciated for its health benefits. Despite its significant economic importance and its value as functional food, onion has been poorly investigated with respect to its genetic diversity. Herein, we surveyed the genetic variation in the “Acquaviva red onion” (ARO), a landrace with a century-old history of cultivation in a small town in the province of Bari (Apulia, Southern of Italy). A set of 11 microsatellite markers were used to explore the genetic variation in a germplasm collection consisting of 13 ARO populations and three common commercial types. Analyses of genetic structure with parametric and non-parametric methods highlighted that the ARO represents a well-defined gene pool, clearly distinct from the Tropea and Montoro landraces with which it is often mistaken. In order to provide a description of bulbs, usually used for fresh consumption, soluble solid content and pungency were evaluated, showing higher sweetness in the ARO with respect to the two above mentioned landraces. Overall, the present study is useful for the future valorization of the ARO, which could be promoted through quality labels which could contribute to limit commercial frauds and improve the income of smallholders.

Kale (Brassica oleracea L. var. acephala) is a widely appreciated vegetable with a century-old history of cultivation in Italy. The present study was addressed to the collection and characterization of kale germplasm traditionally cultivated in Apulia, Southern Italy, nowadays at risk of genetic erosion. In total, nineteen Apulian kale accessions were acquired. Genotyping by means of simple sequence repeat (SSR) DNA markers led to the identification of highly informative primer combinations and highlighted significant patterns of molecular variation among accessions. Consistently, significant differences were observed with respect to morpho-agronomic traits, including yield and harvesting time, and the content of bioactive compounds, namely total phenols, flavonoids, and anthocyanins, associated with antioxidant activity. Overall, this study led to the establishment of an ex situ collection of great importance to preserve endangered Apulian kale germplasm and to provide seed access to potential growers. Meanwhile, it offers a first characterization of Apulian kale, useful to promote its consumption and valorisation through breeding programmes.

Genetic structure and distinctive features of landraces, such as adaptability to local agro-ecosystems and specific qualitative profiles, can be substantially altered by the massive introduction of allochthonous germplasm. The landrace known as “Cipolla rossa di Acquaviva” (Acquaviva red onion, further referred to as ARO) is traditionally cultivated and propagated in a small area of the Apulia region (southern Italy). However, the recent rise of its market value and cultivation area is possibly causing genetic contamination with foreign propagating material. In this work, genotyping-by-sequencing (GBS) was used to characterize genetic variation of seven onion populations commercialized as ARO, as well as one population of the landrace “Montoro” (M), which is phenotypically similar, but originates from another cultivation area and displays different qualitative features. A panel of 5011 SNP markers was used to perform parametric and non-parametric genetic structure analyses, which supported the hypothesis of genetic contamination of germplasm commercialized as ARO with a gene pool including the M landrace. Four ARO populations formed a core genetic group, homogeneous and clearly distinct from the other ARO and M populations. Conversely, the remaining three ARO populations did not display significant differences with the M population. A set of private alleles for the ARO core genetic group was identified, indicating the possibility to trace the ARO landrace by means of a SNP-based molecular barcode. Overall, the results of this study provide a framework for further breeding activities and the traceability of the ARO landrace.