SUMMARY
Tomatoes are one of the most consumed vegetables in the world the whole year through. It is for this reason that the tomato has become an important source of minerals and nutraceutics (mainly carotenoids and vitamin C), which play a key role in human health. It has recently been proved just how important tomato vitamins and carotenoids are in helping to prevent certain cancers and cardiovascular diseases. These diseases have a great impact on the human mortality rate due to modern health-care practices. Taking this fact into account, the trials to improve the nutraceutic content of tomato are truly of utmost interest. 

In recent years, FAO and Bioversity International (formerly the International Plant Genetic Resources Institute) have been promoting the sustainable use of biodiversity in programmes, thus contributing to food security and human nutrition, while at the same time raising awareness of the importance of this link to sustainable development. Following these guidelines, the first work of this thesis contributed to bring new insight in the research field of biodiversity, nutrition and food composition, evaluating the carotenoids and ascorbic acid content in a collection of underutilized tomato cultivars and related accessions to recover their use (directly in fields or as variability sources to obtain new cultivars). A total of 49 accessions of tomato germplasm (14 accessions of common tomato types, 28 cherry type tomatoes and 7 accessions of the related species Solanum pimpinellifolium) from 24 countries were evaluated. Fourteen accessions of the cherry type and two of the common tomato type were selected for their high and balanced nutritional properties, which makes them of great interest for direct human consumption. Furthermore, two accessions of the cherry types with over 1.5 times the normal average ascorbic acid content, as well as one S. pimpinellifolium accession, which presented more than nine times the normal average lycopene content, will most likely be of interest as donor parents for breeding programmes to increase the nutraceutical properties of commercial varieties.

Once sources of variability for high lycopene, β-carotene and ascorbic acid accumulation have been identified, it is necessary to evaluate their real breeding potential in different environments and growing cycles to investigate the nature of the genotype, environment and G × E interaction effects in the expression of these traits. It is also important to determine the genetic control and mode of inheritance in order to use them effectively in breeding programs. In the second work of this thesis, 10 accessions that were preselected for being of potential interest were evaluated in three growing environments. The content of lycopene, β-carotene and ascorbic acid detected was very high in some accessions (up to 281, 35 and 346 mg kg−1, respectively). The important differences in the three environments studied (with some stressing conditions in several situations) had a remarkable influence in the phenotypic expression of the functional characters evaluated. Nevertheless, the major contribution came from the genotypic effect along with a considerable G × E interaction. The joint accumulation of lycopene and β-carotene has a high genetic component. It is possible to select elite genotypes with high contents of both carotenoids in tomato breeding programmes, but multi-environment trials are recommended. The improvement of ascorbic acid content is more difficult because the interference of uncontrolled factors masks the real genetic potential. Among the accessions evaluated, there are four accessions with an amazing genetic potential for functional properties. Three of them belong to S. pimpinellifolium (CDP1568, CDP7090 and CDP9822) and are especially interesting for their use as donor parents in the improvement of carotenoid content in cultivated tomato. The accession CDP4777 (Solanum lycopersicum var cerasiforme) showed a very high genotypic potential for β-carotene and ascorbic acid accumulation and a high stability in their expression, so it might be used either as donor parent in breeding programmes or for direct consumption in quality markets. Of these accessions, CDP4777 was selected to analyze the genetic control and the mode of inheritance of β-carotene and ascorbic acid accumulation because it was of the same species than cultivated tomato. The breeding line CDP8779 (just evaluated before) and the accession CDP4777 were used as parentals, and their F1, F2, BC1 and BC2 descendant generations were obtained. The study was carried out in two locations with different growing conditions (open air and protected by glasshouse cultivation). The genetic control of these trait expressions was studied using an additive, dominance and additive x additive model that includes genotype x environment interactions. The results indicate that β-carotene accumulation was mainly additive (32.2% of the genetic component) with a small dominant component (4.2%) and an important AxE interaction contribution (63.6%), which, in target environments with moderate to high temperatures and no depressed radiation, could substantially enhance β-carotene content. This trait showed a high narrow-sense heritability (h2 = 0.62). Ascorbic acid accumulation was also mainly additive (61.7% of the genetic component) with a minor additive epistatic component (21.5%). This epistatic effect caused a negative heterosis that reduces the positive main additive effect. Nevertheless, in the described target environments, the AxE interaction contribution (16.8%) may enhance the ascorbic acid content and compensate the negative heterosis effect. The total narrow-sense heritability of this trait can be considered good (h2 = 0.52). In conclusion, the CDP4777 accession is a very interesting donor parent for joint improvement of β-carotene (without diminishing the lycopene content) and ascorbic acid content in commercial tomato nutraceutical breeding programmes; the F1 hybrids derived from this accession showed nearly 450% of the commonly reported average β-carotene content and close to 130% of the ascorbic acid content of the female parent.

 In the advanced stages of tomato breeding programmes, where the differences between breeding lines for the carotenoid content become more subtle, a fast and accurate analytical technique, able to separate individual compounds, would be very helpful. In this respect, HPLC, despite being a widespread and popular technique, requires long analysis time, high amounts solvents and expensive analytical columns. These reasons encouraged us to develop an alternative method based on capillary electrochromatography (CEC) with a methacrylate lauryl ester-based monolithic column. By means of this technique, a fast separation of the mentioned analytes was achieved in less than 5 min in a mobile phase containing 35% THF, 30% ACN, 30% methanol and 5% of a 5 mM Tris aqueous buffer, pH 8. The CEC method was evaluated in terms of detection limit and reproducibility, with values below 1.6 mg/mL and 7.2%, respectively.