Lycopene content and color index of tomatoes are affected by the greenhouse cover

The use of plastic or glass covers in greenhouses increases fruit yield and quality by controlling their environment. Color as well as lycopene content is the most important factors in the visual and nutraceutical quality of tomatoes, and they are factors affected by temperature and light inside the greenhouse. The objective of this study was to compare color development and lycopene accumulation in tomato fruits cv. 'Geronimo' at different maturity stages, grown in greenhouses covered with two types of covers (double-layer polyethylene K50 Clear+K50 IR/AC or flat glass 4 mm thick coated with a 15% CaCO3 solution) in different periods of production. At 21, 25 and 29 weeks after transplanting, 24 clusters of tomatoes were labeled per experimental unit and three weeks after labeling, tomato fruits were harvested, classified by maturity, and analyzed for color index (a*/b*) and lycopene content. External and internal temperatures and light data were recorded through a meteorological station system with automatic control. Our results suggested that the season of production, temperature and lighting conditions in the greenhouse, affected the lycopene biosynthesis process. Lycopene content increased as the photoperiod was expanded and at the 32nd week, was higher in fruits collected in greenhouses with double layer of polyethylene (414 mu g g(-1) freeze-dried fruit) than that in fruits grown under a covered with flat glass coated with CaCO3 (241 mu g g(-1) freeze-dried fruit). The application of 15% CaCO3 solution helped to control the temperature but limited the lycopene biosynthesis. Tomato fruits that received greater amounts of light accumulated more lycopene and had the highest color index (1.22) which shows that it is possible that the accumulation of more lycopene is correlated to the transmittance of the cover. The temperature control through bleaching, washing and shading techniques could be improved if the light intensity needed to improve the fruit color development and lycopene accumulation is considered. (C) 2013 Elsevier B.V. All rights reserved.