Analysis of the changes in quality in mandarin fruit, produced by deficit irrigation treatments Josefa M. Navarro * , Juan G. Pérez-Pérez, Pascual Romero, Pablo Botía Departamento Citricultura, Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (IMIDA), C/Mayor s/n La Alberca 30150, Murcia, Spain article info Article history: Received 14 January 2009 Received in revised form 3 July 2009 Accepted 15 September 2009 Keywords: TSS Acidity Maturity index Sugar accumulation Total phenolics Carotenoids Ascorbic acid Antioxidant activity ‘Cleopatra’ mandarin ‘Carrizo’ citrange abstract ‘Clemenules’ mandarin citrus trees, grafted on Cleopatra and Carrizo rootstocks, were subjected to three irrigation treatments: the control (100% ETc), and phases II and III treatments (non-irrigation during phases II and III, respectively). The two deficit irrigation (DI) treatments affected in different ways some fruit quality parameters and these effects were also dependent on the rootstock. Although phase II treat- ment increased total soluble solids (TSS) and titratable acidity (TA), it delayed the maturation process. Phase II-stressed fruits on Carrizo had more fructose and glucose but less sucrose in relation to control fruits, thus increasing the reducing sugars. Phase II-stressed fruits on Cleopatra had more glucose, fruc- tose and sucrose, for osmotic adjustment, also increasing the reducing sugars in these fruits. Phase III- stressed fruits had greater acidity, TSS, total phenolics, lycopene, glucose and sucrose than control fruits, but the same maturation state. In conclusion, DI in phase III improved fruit quality, by increasing the val- ues of important quality parameters related to taste, flavour and nutritional benefits, but DI in phase II produced a drastic delay in the maturation process that made fruits non-commercial. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Citrus trees are cultivated widely in semi-arid climates, where the scarcity of water resources is the major factor limiting irrigated agriculture. One way to optimise water resources is to employ def- icit irrigation (DI) strategies, in which moderate water stress is ap- plied during part of the seasonal cycle of plant development (Kriedemann & Goodwin, 2003). The fruit quality of citrus is affected by water stress, due to changes in juice properties, such as increases in sugar concentra- tions and acidity (Chartzoulakis, Michelakis, & Stefanoudaki, 1999), which reduce, in some cases, the fruit quality (Mougheith, El-Ashram, Amerhom, & Madbouly, 1977). For example, Clemen- tine citrus trees exhibit decreased fruit quality, depending on the phenological stage at which the DI is applied (Romero et al., 2006). Also, water stress resulting from mechanical injury inflicted on secondary scaffolds could improve the quality of citrus (Moon, Mizutani, Rutto, & Bhusal, 2001). Fruit quality is also influenced by the rootstock (Albrigo, 1977; Barry, Castle, & Davies, 2004). Inherent rootstock differences affect- ing plant–water relations are associated with differential sugar accumulation of citrus fruits, which are proposed as a primary cause of differences in quality among citrus rootstocks (Barry et al., 2004). The tree foliage supplies carbohydrates to the fruit but the rootstock determines the amount (Gardner, 1969). It is not clear how rootstocks exert their influence on the juice quality of Citrus species, but plant–water relations are important factors in this (Castle, 1995). ‘Carrizo’ citrange and ‘Cleopatra’ mandarin, the most common rootstocks employed in Spain, have differing char- acteristics, resulting in different responses of quality (Pérez-Pérez, Romero, Navarro, & Botía, 2008; Romero et al., 2006). In order to apply the optimum DI strategy, a good knowledge of the effects of DI in different phenological stages on fruit quality is necessary. To evaluate the sensitivity of different fruit-growth phases to DI in a semi-arid environment, some important fruit quality parameters were evaluated in field-grown ‘Clementine’ cit- rus trees grafted on ‘Cleopatra’ mandarin or ‘Carrizo’ citrange, two rootstocks with differing sensitivities to drought. 2. Materials and methods 2.1. Plant material The study was carried out during 2003 in Murcia (southern Spain), on 10-year-old citrus trees (Citrus reticulata Blanco) grafted on two rootstocks, ‘Cleopatra’ mandarin (Citrus reshni Hort. ex 0308-8146/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2009.09.048 * Corresponding author. Tel.: +34 968366759; fax: +34 968366792. E-mail address: josefam.navarro2@carm.es (J.M. Navarro). Food Chemistry 119 (2010) 1591–1596 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem