Breeding Tomatoes with Higher Flavonoids and Phenolics Content

Flavonoids and phenolics include compounds found in fruits and vegetables with multiple functions, including potential benefits to human health. Among their properties, they may potentially be anti-allergic, anti-inflammatory, antimicrobial, anticarcinogenic, and antioxidant. Flavonoids and phenolics may act as pathogen deterrents, mitigate environmental stresses, and serve as pigments that attract pollinators and seed dispersers to flowers and ripe fruit. Tomatoes are an excellent source of carotenoids but are relatively low in flavonoids and phenolics in the fruit. Wild relatives of tomato do express fruit anthocyanins as well as other flavonoids and associated phenolics. Genes controlling fruit anthocyanin expression have been introgressed into tomato from at least four wild species. Three of these (Aubergine [Abg], Anthocyanin Fruit [Aft] and atroviolaceum [atv]) have been named and characterized. Phenotypic expression in a cultivated background is rather weak, but when either Abg or Aft was combined with atv, anthocyanin expression was significantly enhanced. Anthocyanin expression was light induced and pigment accumulated only in the skin. Amounts ranged up to 10 mg/100 g FW on a whole fruit basis (normal tomato fruits have no anthocyanin). Other flavonoid and phenolic compounds were elevated in these types as well, possessing up to 70 mg/100 g FW compared to 40 mg/ 100 g FW for normal tomatoes. High anthocyanin tomatoes showed high antioxidant potential, with the water soluble fraction showing approximately 10-fold higher antioxidant activity than the lipid soluble fraction that contains carotenoids. A structural gene, anthocyanin without (aw) blocks anthocyanin expression but allows accumulation of flavonols upstream in the biosynthetic pathway. When aw was combined with Aft and atv, anthocyanin expression was reduced or eliminated, but total flavonoids and phenolics remained unchanged. Thus, it is possible to obtain tomatoes with near normal fruit color but elevated flavonoids and phenolics. In 2011, ‘Indigo Rose’ was released as the first high anthocyanin fruit tomato. Further increases in these types of compounds may be possible through evaluation and introgression from Solanum lycopersicum var. cerasiforme accessions.