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Plant specialized metabolites (SMs) play an important role in the interaction with the environment and are part of the plant defense response. These natural products are volatile, semi-volatile and non-volatile compounds produced from common building blocks deriving from primary metabolic pathways and rapidly evolved to allow a better adaptation of plants to environmental cues. Specialized metabolites include terpenes, flavonoids, alkaloids, glucosinolates, tannins, resins, etc. that can be used as phytochemicals, food additives, flavoring agents and pharmaceutical compounds. This review will be focused on Mediterranean crop plants as a source of SMs, with a special attention on the strategies that can be used to modulate their production, including abiotic stresses, interaction with beneficial soil microorganisms and novel genetic approaches.

Tomato is a high value crop and the primary model for fleshy fruit development and ripening. Breeding priorities include increased fruit quality, shelf life and tolerance to stresses. To contribute towards this goal, we re-sequenced the genomes of Corbarino (COR) and Lucariello (LUC) landraces, which both possess the traits of plant adaptation to water deficit, prolonged fruit shelf-life and good fruit quality. Through the newly developed pipeline Reconstructor, we generated the genome sequences of COR and LUC using datasets of 65.8 M and 56.4 M of 30–150 bp paired-end reads, respectively. New contigs including reads that could not be mapped to the tomato reference genome were assembled, and a total of 43, 054 and 44, 579 gene loci were annotated in COR and LUC. Both genomes showed novel regions with similarity to Solanum pimpinellifolium and Solanum pennellii. In addition to small deletions and insertions, 2, 000 and 1, 700 single nucleotide polymorphisms (SNPs) could exert potentially disruptive effects on 1, 371 and 1, 201 genes in COR and LUC, respectively. A detailed survey of the SNPs occurring in fruit quality, shelf life and stress tolerance related-genes identified several candidates of potential relevance. Variations in ethylene response components may concur in determining peculiar phenotypes of COR and LUC.

International audience; Although tomato flavor has not been a major goal for breeders, nowadays it becomes important as it is a subject of consumer complaint. A better knowledge of tomato consumer preferences, at the European level, should provide the basis for improvement of fruit quality and for market segmentation. In the framework of a large European project, 806 consumers from 3 countries, The Netherlands, France, and Italy, were presented with a set of 16 varieties representing the diversity of fresh tomato offer in order to evaluate their preferences. In parallel, sensory profiles were constructed by expert panels in each country. Preference maps were then constructed in each country revealing the structure of consumer preferences and allowing identification of the most important characteristics. Then a global analysis revealed that preferences were quite homogeneous across countries. This study identified the overall flavor and firmness as the most important traits for improving tomato fruit quality. It showed that consumer preferences from different European countries, with different cultures and food practices, are segmented following similar patterns when projected onto a common referential plan. Moreover, the results clearly showed that diversification of taste and texture is required to satisfy all consumers' expectations as some consumers preferred firm tomatoes, while others preferred melting ones and were more or less demanding in terms of sweetness and flavor intensity. Detailed comparisons also showed the importance of the fruit appearance in consumer preference. Practical Application: The consumer preferences for fresh market tomato were studied in 3 European countries. The main descriptors for further breeding for consumer satisfaction were identified. Four clusters of consumers were identified in the overall analysis, the 3 countries contributing the same way to each cluster. The impact of appearance in the preferences was also underlined.

International audience; Sensory properties are important elements to evaluate the qualities of vegetable products and are also determinant factors in purchasing decision. Here we report the Italian results of a preference mapping study conducted within a larger European project with the aim of describing the preferences of European consumers in regard to the diversity of traditional and modern tomato varieties, available on the market. This study has allowed the assessment of fruit quality at 3 levels: objective description of sensory properties, consumer preference tests, and physicochemical measurements. A set of 16 tomato cultivars, with different fruit sizes and shapes, was described and classified according to 18 sensory attributes including flavor, appearance, and texture characteristics. The same cultivars were evaluated by 179 consumers in a “preference mapping” experiment with the goal of identifying the preferred varieties and the reasons for the choice. The consumer data are referred to hedonic ratings (aspect liking and overall liking), familiarity for the analyzed cultivars, and individual features collected by a questionnaire. A hierarchical analysis of the clusters allowed to distinguish, within the sampled Italian consumers, 4 segments with different preferences which represented 19%, 25%, 41%, and 15% of the population, respectively. A partial least square regression model allowed the identification of the sensory attributes that best described consumer cluster preferences for tomato cultivars. Both texture and flavor descriptors were important drivers of consumer preferences, but the relevance (predictive value) of individual descriptors to model tomato liking was different for each consumer segment. Information on demographic and behavioral characteristics, usage habits, and factors relevant for purchasing were also provided on the 4 groups of consumers.

Tomato is a model species for genetic analyses since a long time. Many mutations controlled by a single gene were discovered and the underlying genes were mapped first on the tomato genetic map. Most of these genes are involved in fruit colour and shape, in plant growth and architecture and in disease resistances. With the construction of high-density molecular genetic maps, many genes were located on the genome and subsequently several of them were fine-mapped and further identified by positional cloning. Today with the availability of the tomato genome sequence these genes are physically located on the genome and the identification of new ones is being considerably accelerated. The alignment of the physical and genetic maps allowed the identification of hot spots of recombination and of large regions where recombination is almost suppressed, whatever the progeny studied. The impact of this heterogeneity in recombination is discussed.

Highlight Over 100 fruit volatile QTLs were identified in a RIL population derived from the red-fruited wild species Solanum pimpinellifolium and a fresh market tomato variety ‘Moneymaker’ and subsequently confirmed in introgression lines., Volatile organic compounds (VOCs) are major determinants of fruit flavor, a primary objective in tomato breeding. A recombinant inbred line (RIL) population consisting of 169 lines derived from a cross between Solanum lycopersicum and a red-fruited wild tomato species Solanum pimpinellifolium accession (SP) was characterized for VOCs in three different seasons. Correlation and hierarchical cluster analyses were performed on the 52 VOCs identified, providing a tool for the putative assignation of individual compounds to metabolic pathways. Quantitative trait locus (QTL) analysis, based on a genetic linkage map comprising 297 single nucleotide polymorphisms (SNPs), revealed 102 QTLs (75% not described previously) corresponding to 39 different VOCs. The SP alleles exerted a positive effect on most of the underlying apocarotenoid volatile QTLs—regarded as desirable for liking tomato—indicating that alleles inherited from SP are a valuable resource for flavor breeding. An introgression line (IL) population developed from the same parental genotypes provided 12 ILs carrying a single SP introgression and covering 85 VOC QTLs, which were characterized at three locations. The results showed that almost half of the QTLs previously identified in the RILs maintained their effect in an IL form, reinforcing the value of these QTLs for flavor/aroma breeding in cultivated tomato.

A major objective in modern biology is deciphering the genetic and molecular bases of natural phenotypic variation. Over the past three decades the tomato clade (Solanum sect. Lycopersicon) has been a model system not only for the identification and positional cloning of quantitative trait loci (QTL), but also for the development of new molecular breeding strategies aimed at a more efficient exploration and exploitation of the rich biodiversity stored in wild germplasm for hundreds of biologically and agronomically relevant quantitative traits. The numerous QTL mapping studies conducted so far have resulted in the detection of several thousands of QTL. Despite this wealth of genetic information, the molecular bases have been revealed for only a handful of major QTL. The release of the tomato genome sequences (Tomato Genome Consortium 2012), along with the rapid development of cost-effective next generation sequencing (NGS) technologies, new mapping resources, and the ever-growing 'omic' platforms, are holding the promise to reverse this trend. This deluge of genomic resources are undoubtedly re-shaping QTL analyses also in this crop, allowing a re-examination of the variation and inheritance of complex traits at the intraspecific level, increasing the spectrum of potentially valuable alleles available for breeding. In this framework, precision phenotyping, advanced bioinformatics tools, as well as public phenotype "warehousing" databases are foreseen as the necessary tools to boost our understanding of the genetic and molecular architecture of quantitative traits, and to guarantee sustainable crop improvements in the face of an ever-growing human population and changing climates.

Semi-polar metabolites such as flavonoids, phenolic acids, and alkaloids are very important health-related compounds in tomato. As a first step to identify genes responsible for the synthesis of semi-polar metabolites, quantitative trait loci (QTLs) that influence the semi-polar metabolite content in red-ripe tomato fruit were identified, by characterizing fruits of a population of introgression lines (ILs) derived from a cross between the cultivated tomato Solanurn lycopersicum and the wild species Solanurn chmielewskii. By analyzing fruits of plants grown at two different locations, we were able to identify robust metabolite QTLs for changes in phenylpropanoid glycoconjugation on chromosome 9, for accumulation of flavonol glycosides on chromosome 5, and for alkaloids on chromosome 7. To further characterize the QTLs we used a combination of genome sequencing, transcriptomics and targeted metabolomics to identify candidate key genes underlying the observed metabolic variation.

International audience; Throughout tomato domestication, a large increase in fruit size was associated with a loss of dry matter and sugar contents. This study aims to dissect the contributions of genetic variation and the physiological processes underlying the relationships between fruit growth and the accumulation of dry matter and sugars. Fruit quality traits and physiological parameters were measured on 20 introgression lines derived from the introgression of Solanum chmielewskii into S. lycopersicum, under high (HL, unpruned trusses) and low (LL, trusses pruned to one fruit) fruit load conditions. Inter- and intra-genotypic correlations among traits were estimated and quantitative trait loci (QTL) for size, composition, and physiological traits were mapped. LL increased almost all traits, but the response of sugar content was genotype-dependent, involving either dilution effects or differences in carbon allocation to sugars. Genotype3fruit load interactions were significant for most traits and only 30% of the QTL were stable under both fruit loads. Many QTL for fresh weight and cell or seed numbers co-localized. Eleven clusters of QTL for fresh weight and dry matter or sugar content were detected, eight with opposite allele effects and three with negative effects. Two genotypic antagonistic relationships, between fresh weight and dry matter content and between cell number and cell size, were significant only under HL; the second could be interpreted as a competition for carbohydrates among cells. The role of cuticular conductance, fruit transpiration or cracking in the relationship between fruit fresh weight and composition was also emphasized at the genetic and physiological levels.

The genome of tomato (Solanum lycopersicum L.) is being sequenced by an international consortium of 10 countries (Korea, China, the United Kingdom, India, the Netherlands, France, Japan, Spain, Italy, and the United States) as part of the larger “International Solanaceae Genome Project (SOL): Systems Approach to Diversity and Adaptation” initiative. The tomato genome sequencing project uses an ordered bacterial artificial chromosome (BAC) approach to generate a high-quality tomato euchromatic genome sequence for use as a reference genome for the Solanaceae and euasterids. Sequence is deposited at GenBank and at the SOL Genomics Network (SGN). Currently, there are around 1000 BACs finished or in progress, representing more than a third of the projected euchromatic portion of the genome. An annotation effort is also underway by the International Tomato Annotation Group. The expected number of genes in the euchromatin is ∼40,000, based on an estimate from a preliminary annotation of 11% of finished sequence. Here, we present this first snapshot of the emerging tomato genome and its annotation, a short comparison with potato (Solanum tuberosum L.) sequence data, and the tools available for the researchers to exploit this new resource are also presented. In the future, whole-genome shotgun techniques will be combined with the BAC-by-BAC approach to cover the entire tomato genome. The high-quality reference euchromatic tomato sequence is expected to be near completion by 2010.

[EN] The long tradition of tomato cultivation in Italy has allowed the evolution of a wide diversity of traditional varieties or landraces that have been cultivated for centuries and many of them are still common in the local markets. Adaptation to peculiar climatic and edaphic conditions, the geographical isolation of several growing areas, the specific agro-technique, the local gardners’ selection, also based on consumers’s sensory preferences, have resulted in groups of landraces distributed not only by region but also by sub-regional areas. In most cases, the cultivation of these Italian landraces covers very limited areas being carried out in family gardens for personal consumption and/or in small-size farms that, therefore, play a key role in the on farm maintenance of this precious germplasm, which in many cases is risking extinction. The Campania region has been, and still is, an important area for tomato production with a long tradition in the selection, cultivation and processing of the crop, resulting in a rich reservoir of valuable tomato landraces. So far, only three Italian tomato landraces have been granted a Protected Geographical Status under European Union law, the PGI “Pomodoro di Pachino” form Sicily, and the two PDOs “Pomodoro S. Marzano dell'Agro Sarnese-Nocerino” and the “Pomodorino del Piennolo del Vesuvio” from Campania. This short review will address some of the most popular landraces of the Campania region, with a particular focus on the two PDOs., [ES] La larga tradición del cultivo del tomate en Italia ha permitido la evolución de una amplia diversidad de variedades tradicionales o variedades autóctonas que han sido cultivadas durante siglos, muchas de las cuales siguen siendo comunes en los mercados locales. La adaptación a las peculiares condiciones climáticas y edáficas, el aislamiento geográfico de varias zonas de cultivo, las técnicas de cultivo específicas, la selección de los agricultores locales, también basada en las preferencias sensoriales de los consumidores, han dado como resultado grupos de variedades locales distribuidas no sólo por regiones, sino por áreas sub-regionales. En la mayoría de los casos, el cultivo de estas variedades autóctonas italianas cubre áreas muy limitadas y se están llevando a cabo en huertos familiares para consumo personal y / o en fincas pequeñas que, por lo tanto, desempeñan un papel clave en el mantenimiento de este valioso germoplasma, que en muchos casos está en peligro de extinción. La región de Campania ha sido, y sigue siendo, un área importante para la producción de tomate con una larga tradición en la selección, cultivo y procesamiento de este cultivo, resultando en un rico reservorio de variedades autóctonas de tomate valiosas. Hasta el momento, sólo tres variedades autóctonas de tomate italiano han obtenido el estatus de protección geográfica conforme a la legislación de la Unión Europea, la IGP “Pomodoro di Pachino” de Sicilia y las dos DOP “Pomodoro S. Marzano dell'Agro Sarnese-Nocerino” y “Pomodorino Del Piennolo del Vesuvio" de Campania. Esta breve revisión abordará algunas de las razas tradicionales más populares de la región de Campania, con especial atención a las dos DOP., This work was supported by the European Commission Horizon 2020 program (TRADITOM grant 634561 to S.G. and P.S.).