A diet rich in vegetables has been associated with a reduced risk of many diseases related to aging and modern lifestyle. Over the past several decades, many researches have pointed out the direct relation between the intake of bioactive compounds present in tomato and a reduced risk of suffering different types of cancer. These bioactive constituents comprise phytochemicals such as carotenoids and polyphenols. The direct intake of these chemoprotective molecules seems to show higher efficiencies when they are ingested in its natural biological matrix than when they are ingested isolated or in dietary supplements. Consequently, there is a growing trend for improvement of the contents of these bioactive compounds in foods. The control of growing environment and processing conditions can ensure the maximum potential accumulation or moderate the loss of bioactive compounds, but the best results are obtained developing new varieties via plant breeding. The modification of single steps of metabolic pathways or their regulation via conventional breeding or genetic engineering has offered excellent results in crops such as tomato. In this review, we analyse the potential of tomato as source of the bioactive constituents with cancer-preventive properties and the result of modern breeding programs as a strategy to increase the levels of these compounds in the diet.

The accumulation of polyphenols and l-ascorbic acid was evaluated under conventional (integrated pest management, IPM) and organic farming, as means to increase the accumulation of chemoprotective compounds. The effect of genotype was considerably higher than the growing system, in fact it is determining. 'Kalvert', a high-lycopene cultivar, outstood for the accumulation of most polyphenols, though low-carotenoid cultivars with high accumulation were also detected. Organic farming significantly increased the levels of caffeic acid by 20%, but reduced those of ferulic acid and naringenin by 13% and 15% respectively. A strong interaction with the environment was detected: in Navarra the differences were limited, while in Extremadura lower contents of ferulic acid and higher contents of chlorogenic acid and rutin were found in organic farming for certain cultivars. The effect of organic farming on l-ascorbic acid was dependent on cultivar and environment and it only led to an increase in Extremadura by 58%.

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13The effect of conventional integrated pest management and organic farming production 14 systems on the agronomic performance and quality of standard and high lycopene tomato cvs. 15 has been evaluated for two years in two of the main processing tomato producing areas of 16 Spain (Extremadura and Navarra). As an average, the production under organic farming was on 17 average 36% lower than in conventional integrated pest management. Organic farming tended 18show reduced contents of citric and glutamic acid. Although the contents in sugars were not 19 significantly affected, the ratios sucrose equivalents to citric and glutamic acid increased. 20Nevertheless, a strong influence of the environment and interactions were detected and under 21 certain conditions (e.g. Extremadura), organic farming may increase the contents in glucose 22and fructose. The levels of lycopene were not affected by the cultivation system, while beta-23 carotene contents were higher under organic farming. High lycopene cvs. 24424' registered the highest lycopene levels, but with 27.6% and 28.1% lower production 25 levels compared to 'H-9036', the cv. with the best agronomic performance. 'Kalvert', with high 26 accumulation of sugars and high ratios sucrose equivalents to citric and glutamic acid and high 27 lycopene contents would be an ideal material for supplying quality markets. 'H-9997' with 28 intermediated levels of lycopene accumulation proved to be a good material combining 29 production levels and functional quality. 'CXD-277' offered the higher values in variables 30 related with organoleptic quality with intermediate lycopene accumulation but with lower 31 production. 32 33

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