Anthocyanins are a large group of water-soluble flavonoid pigments. These specialized metabolites are ubiquitous in the plant kingdom and play an essential role not only in plant reproduction and ...dispersal but also in responses to biotic and abiotic stresses. Anthocyanins are recognized as important health-promoting and chronic-disease-preventing components in the human diet. Therefore, interest in developing food crops with improved levels and compositions of these important nutraceuticals is growing. This review focuses on work conducted to elucidate the genetic control of the anthocyanin pathway and modulate anthocyanin content in eggplant (Solanum melongena L.) and tomato (Solanum lycopersicum L.), two solanaceous fruit vegetables of worldwide relevance. While anthocyanin levels in eggplant fruit have always been an important quality trait, anthocyanin-based, purple-fruited tomato cultivars are currently a novelty. As detailed in this review, this difference in the anthocyanin content of the cultivated germplasm has largely influenced genetic studies as well as breeding and transgenic approaches to improve the anthocyanin content/profile of these two important solanaceous crops. The information provided should be of help to researchers and breeders in devising strategies to address the increasing consumer demand for nutraceutical foods.
The maturation and ripening of fleshy fruits is a developmental program that synchronizes seed maturation with metabolism, rendering fruit tissues desirable to seed dispersing organisms. Through RNA ...interference repression, we show that Tomato AGAMOUS-LIKE1 (TAGL1), the tomato (Solanum lycopersicum) ortholog of the duplicated SHATTERPROOF (SHP) MADS box genes of Arabidopsis thaliana, is necessary for fruit ripening. Tomato plants with reduced TAGL1 mRNA produced yellow-orange fruit with reduced carotenoids and thin pericarps. These fruit are also decreased in ethylene, indicating a comprehensive inhibition of maturation mediated through reduced ACC Synthase 2 expression. Furthermore, ectopic expression of TAGL1 in tomato resulted in expansion of sepals and accumulation of lycopene, supporting the role of TAGL1 in ripening. In Arabidopsis, the duplicate SHP1 and SHP2 MADS box genes regulate the development of separation layers essential for pod shatter. Expression of TAGL1 in Arabidopsis failed to completely rescue the shp1 shp2 mutant phenotypes, indicating that TAGL1 has evolved distinct molecular functions compared with its Arabidopsis counterparts. These analyses demonstrate that TAGL1 plays an important role in regulating both fleshy fruit expansion and the ripening process that together are necessary to promote seed dispersal of fleshy fruit. From this broad perspective, SHP1/2 and TAGL1, while distinct in molecular function, regulate similar activities via their necessity for seed dispersal in Arabidopsis and tomato, respectively.
The color of tomato fruit is mainly determined by carotenoids and flavonoids. Phenotypic analysis of an introgression line (IL) population derived from a cross between Solanum lycopersicum ...'Moneyberg' and the wild species Solanum chmielewskii revealed three ILs with a pink fruit color. These lines had a homozygous S. chmielewskii introgression on the short arm of chromosome 1, consistent with the position of the y (yellow) mutation known to result in colorless epidermis, and hence pink-colored fruit, when combined with a red flesh. Metabolic analysis showed that pink fruit lack the ripening-dependent accumulation of the yellow-colored flavonoid naringenin chalcone in the fruit peel, while carotenoid levels are not affected. The expression of all genes encoding biosynthetic enzymes involved in the production of the flavonol rutin from naringenin chalcone was down-regulated in pink fruit, suggesting that the candidate gene underlying the pink phenotype encodes a regulatory protein such as a transcription factor rather than a biosynthetic enzyme. Of 26 MYB and basic helix-loop-helix transcription factors putatively involved in regulating transcription of genes in the phenylpropanoid and/or flavonoid pathway, only the expression level of the MYB12 gene correlated well with the decrease in the expression of structural flavonoid genes in peel samples of pink- and red-fruited genotypes during ripening. Genetic mapping and segregation analysis showed that MYB12 is located on chromosome 1 and segregates perfectly with the characteristic pink fruit color. Virus-induced gene silencing of SlMYB12 resulted in a decrease in the accumulation of naringenin chalcone, a phenotype consistent with the pink-colored tomato fruit of IL1b. In conclusion, biochemical and molecular data, gene mapping, segregation analysis, and virus-induced gene silencing experiments demonstrate that the MYB12 transcription factor plays an important role in regulating the flavonoid pathway in tomato fruit and suggest strongly that SlMYB12 is a likely candidate for the y mutation.
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.
: 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.
Quantitative trait locus (QTL) genetics retains an important role in the study of biological and agronomic processes; however, its genetic resolution is often comparatively low. Community-based ...strategies are thus required to address this issue. Here we detail such a strategy wherein the widely used Solanum pennellii introgression lines (ILs) in the genetic background of the cultivated tomato (Solanum lycopersicum) are broken up into molecular marker-defined sublines as a community resource for map-based cloning.
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 Solanum lycopersicum and the wild species Solanum 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.
Domestication of many plants has correlated with dramatic increases in fruit size. In tomato, one quantitative trait locus (QTL), fw2.2, was responsible for a large step in this process. When ...transformed into large-fruited cultivars, a cosmid derived from the fw2.2 region of a small-fruited wild species reduced fruit size by the predicted amount and had the gene action expected for fw2.2. The cause of the QTL effect is a single gene, ORFX, that is expressed early in floral development, controls carpel cell number, and has a sequence suggesting structural similarity to the human oncogene c-H-ras p21. Alterations in fruit size, imparted by fw2.2 alleles, are most likely due to changes in regulation rather than in the sequence and structure of the encoded protein.
This study aimed at providing further insights into the positive and negative drivers of tomato liking. For this purpose, 13 tomato cultivars representing different typologies were characterized for ...physicochemical parameters and aroma volatiles, and were assessed by a trained panel for sensory descriptors, and by Italian consumers for liking. The relationships among the different parameters and their effects on consumer liking were studied by Partial Least Squares (PLS) analysis. Among physicochemical traits and sensory descriptors, seeds, reducing sugars, firmness, thick epicarp, soluble solids, sour taste, total acidity, citrate, herbaceous aroma and brightness were found to be drivers of liking, whereas pulp thickness, humidity, fruit weight, diacetyl-like odor and mealiness showed an opposite influence. For the aroma volatiles, 2-isobutylthiazole played a key role on liking and its positive contribution seemed to be supported by (Z)-3-hexen-1-ol, but suppressed by 6-methyl-5-hepten-2-ol, especially when tomatoes had a poor volatile fraction. These results represent a contribution to the knowledge that could lead to more effective breeding strategies aimed at improving tomato sensory quality.
► Sensory quality of 13 commercial and local tomato cultivars was assessed at 4 levels. ► To simplify data complexity a two-step regression model of tomato liking was created. ► Consumers overall liking involved multiple sensory and compositional variables. ► Brix, sugars, acidity, citrate, firmness and green flavour positively impact liking. ► 2-isobutylthiazole is at least 6% of the overall volatiles in the most liked tomatoes.
European long shelf-life (LSL) tomato landraces can be classified into two main groups: the Italian group, including ‘Piennolo’ landraces, and the Spanish group, including the ‘Penjar’ and ‘Ramellet’ ...landraces. In this study, a partially common set of ‘Piennolo’ and ‘Penjar-Ramellet’ varieties was grown in Italy and Spain to evaluate the effect of different agro-environmental and storage conditions on fruit quality and shelf-life. Overall, both Italian and Spanish LSL genotypes lost their peculiar phenotype in terms of physicochemical properties and shelf-life behavior when not grown in their original agro-environment. To better understand the sensory attributes that drive consumers’ preferences, all varieties were characterized using descriptive sensory analysis combined with hedonic tests. The evaluations were conducted postharvest on raw and processed products according to the country’s culinary tradition (baked in Italy; spread on bread in Spain). Sensory description by trained panels conducted on raw and processed products highlighted different sensory profiles between the two LSL tomato groups. In the ‘Piennolo’ group, a reduction in sensory diversity among the genotypes was observed in the baked products compared to the raw ones, while this trend was not observed for the ‘Penjar-Ramellet’ group. None of the varieties fully met the consumers’ preferences.
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