Preharvest illumination of cherry tomato reduces ripening period, enhances fruit carotenoid concentration and overall fruit quality

The prevention of certain chronic diseases has been related to tomato (Solanum lycopersicum L.) consumption. The demand for high-quality tomatoes has, therefore, increased rapidly. As a climacteric fruit, tomato will only ripen to full colour postharvest. Trusses of mature-green greenhouse tomatoes of a red ('Cherry Little Wonder') and a yellow cultivar ('Goldilocks') were illuminated, preharvest, with either red (RL) (peak at 634 nm, 120 +/- 20 mu mol m(-2) s(-1)) or blue (BL) LED lights (peak at 450 nm, 120 +/- 20 mu mol m(-2) s(-1)) for 8 h per day for seven consecutive days. These on-plant RL and BL treatments significantly affected fruit colour and pigment concentration. Both light treatments enhanced the accumulation of lycopene, thereby significantly enhancing the nutritive value of the fruit. Similarly to lycopene, the beta-carotene concentrations also increased following RL and BL exposure, again more so in the red than the yellow cultivar. Both light treatments also enhanced the speed of colour change by 5 days for the red and by 10 days for the yellow cultivar, resulting in either the desired red or the yellow colour. Our findings could be employed to improve quality and shorten the ripening period of tomato, while mechanisms involved in the biosynthesis and accumulation of these carotenoids require further investigation.