Fruit load or fruit position alters response to temperature and subsequently cherry tomato quality

Changes in fruit-source ratio during the growth and maturation of cherry tomato fruits were studied in combination with increased fruit temperature. Six treatments were compared: the presence or absence of local heating combined with different fruit origins (7P, fruit from trusses pruned to seven flowers; 14P, proximal fruits; 14D, distal fruits from trusses pruned to 14 flowers). 7P were less sensitive to heating whereas 14P and 14D showed greater reduction in water and dry matter (DM) content. Distal fruits had the lowest structural DM (sDM), which could be due to a lower fruit cell number. Heating further decreased the sDM, so that fruit sink size was the lowest for distal fruits subjected to heating. Under low competition (7P), heating had a beneficial effect on sugar and lycopene content, whereas acids, beta-carotene and vitamin C content were reduced. Under high competition (14P, 14D), heating increased the ratio sDM-DM. This was mainly due to the reduced content of sugars and acids, but also to the reduced accumulation of secondary metabolites such as vitamin C, P-carotene and lycopene. This study underlines the interactions between fruit temperature and the fruit-source ratio and the consequences for fruit composition and nutritional quality. (c) 2005 Society of Chemical Industry.