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  • Author or Editor: Peter J. Mes x
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Tomato lines carrying the genes Aft, atv, Abg, hp-1, and an as yet undetermined gene from the introgression line LA2099 have been combined to produce fruit with elevated anthocyanin content. The antioxidant activity of juice made from anthocyanin-expressing tomatoes was compared to juices made from tomatoes with varied carotenoid content. The contribution of anthocyanin to the total antioxidant activity of the whole fruit in current material is small, but with potential for significant improvement. The increase in flavonoids in the elevated anthocyanin lines has increased water-soluble antioxidant activity of the fruit in vitro.

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Cultivated tomatoes (Solanum lycopersicum L.) produce anthocyanins in vegetative tissues and certain flavonols can be found in the fruit. Some related wild species do produce anthocyanins in the fruit, and this trait has been transferred into cultivated tomato. Fruit with the genes Abg, Aft, and atv exhibit varying degrees of anthocyanin production in the epidermis, but not in the fruit pericarp. Fruit with these alleles in various combinations were analyzed to characterize the anthocyanidin profile, moieties, and total anthocyanin content. In general, combining atv with either Aft or Abg substantially increased anthocyanin production in the fruit. Over 23 different anthocyanins were detected, petunidin-3-(p-coumaryl)-rutinoside-5-glucoside being predominant. The highest level of anthocyanin expression was observed in small fruit with the genotype Abg- atvatv and AftAft atvatv, well in excess of 100 mg/100 g fresh weight of epidermis and subepidermis depending on the size of the fruit. Nonanthocyanin flavonoids were also upregulated in proportion to the anthocyanin concentration. The anthocyanin genes were also combined with genes affecting carotenoid composition and content. Reduced carotenoid content conditioned by the alleles B (Beta) and r (yellow flesh) was associated with lower total anthocyanins, an unexpected observation because the carotenoid and anthocyanin pathways are thought to be independent. The level of anthocyanin did not affect carotenoid profiles or amounts.

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A nutritional study was initiated to determine which carotenoids found in tomato result in decreased lipid oxidation ex vivo. To compare the carotenoids in a human diet without the use of purified supplements, tomatoes expressing nonfunctional enzymes in the carotenoid pathway were used. Tomato lines carrying the genes t, B, ogc, Del, or r were grown to produce fruit containing with high levels of prolycopene, beta-carotene, lycopene, or delta-carotene respectively, or low total carotenoids in r. Juices were processed from these lines and used in a dietary intervention study. Plasma samples were drawn before and after consumption of each juice. These samples were subjected to a battery of tests to analyze the contribution of carotenoids to the total lipid antioxidant status. Results of these tests are discussed.

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The major markets for cowpea are seed sales and processing. During the storage period prior to sales, some seedcoats of `Mississippi Silver' darken from tan to varying shades of brown. This darkening is undesirable for the processing market, since it results in an unattractive product lacking uniformity. A series of studies was undertaken to investigate this problem. It was noted that darkening proceeded at a rapid rate when seed were left in the field after drying. Selection against darkening was unsuccessful, and attempts at extracting the colored compound with polar and nonpolar solvents were inconclusive. A method of screening for the darkening trait was devised. It was found that darkening could be induced by exposing seed to a high-oxygen environment, suggesting that oxidation is involved in the darkening process. In support of this, it was found that the lowest rate of darkening occurred when the seed were placed in an enriched nitrogen chamber after harvest.

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