Oranges are a rich source of bioactive compounds with recognized benefits for human health. To guarantee high quality and production levels, citrus farms usually employ the combination of selected cultivars with well adapted rootstocks. This study analyzes the impact of four different citrus rootstocks (Forner-Alcaide no.5, ‘Cleopatra mandarin’, Citrus volkameriana and Carrizo citrange) on the bioactive compounds and antioxidant activity of two orange cultivars (‘Salustiana’ and ‘Sanguinelli’) widely used in the orange juice industry. For the hydrophilic fraction, the phenolic compound, anthocyanin, and organic acid profiles were determined by HPLC-DAD-HRMS, and the antioxidant activity by ABTS, DPPH, and ORAC assays. Besides, the total carotenoids and ABTS concentrations were calculated for the hydrophobic fraction. A set of three flavanones, one flavone, and eight anthocyanins were tentatively identified and quantified in the orange cultivars tested. The predominant phenolic compounds obtained in both orange cultivars were hesperidin and narirutin, while cyanidin-3-O-(6″-malonyl) glucoside followed by cyanidin-3-O-rutinoside and cyanidin-3-O-glucoside were the main anthocyanins found in the ‘Sanguinelli’ cultivar. Citric acid, followed by malic, oxalic, and ascorbic acids were the main organic acids. The higher amount of antioxidant compounds was found in fruit from the Forner-Alcaide no.5 rootstock. These results indicate that Forner-Alcaide n.5 affects positively the phenolic and organic acid composition and the antioxidant capacity of ‘Sanguinelli’ and ‘Salustiana’ cultivars, and is therefore a good option for the sector based on the healthy promoting properties.

Drought and flooding conditions are increasingly common abiotic factors that affect citrus crops in both the Mediterranean Basin and Florida. Furthermore, emerging diseases, such as Huanglongbing (HLB), are a potential risk for these crops in those producing areas. This study aimed to evaluate the behavior under water-stress treatments of three new citrus rootstocks (UFR-6, B11R5T60, and 2247 x 6070-02-2) with reported tolerance of HLB, comparing them with a common commercial citrus rootstock (Carrizo citrange). Four water conditions were established: Control, Medium Water Stress (MWS), Drought, and Flooding. Chlorophyll index (SPAD), growth in height, relative growth rate, biomass (fresh and dry weight) and plant water status were evaluated. Citru rootstock response were different for each genotype; Carrizo citrange was negatively affected by all water treatments in the chlorophyll index (SPAD) and biomass production. By contrast, UFR-6 showed a positive response in SPAD and growth under MWS and Drought, B11R5T60 displayed similar behavior to Control under all water stresses, and the response of 2247 x 6070-02-2 under MWS treatment was adequate but was not under Drought or Flooding conditions. Our study describes the behavior of these promising new citrus rootstocks against water stress; B11R5T60 exhibiting the best performance. These results can be useful for the citrus industry to address water-stress problems in these crops.

Salinity is a major agriculture problem for citrus in the Mediterranean basin, which is a major global producer region. Citrus crops are also threatened by emerging diseases such as Huanglongbing (HLB). The use of different rootstocks increases the variability of citrus plant material in orchards, thus preventing extensive damage caused by abiotic and/or biotic diseases. In this work, we have evaluated the salinity response of five citrus rootstocks (US942, US897, X639, Forner Alcaide No. 5 and Carrizo citrange) some of which have known tolerance to HLB, under Mediterranean conditions. Four treatments with different salt concentrations (0, 25, 50 and 75 mM of NaCl) were applied by watering the plants three times per week for eleven weeks. Chlorophyll index (SPAD), growth and plant symptom parameters were recorded on a biweekly basis. At the end of the trial, roots, stem and leaves biomass and plant mineral content were obtained. The increasing concentration of NaCl resulted in visible leave damage symptoms for all citrus rootstocks assayed, hindering plant growth in all citrus rootstocks assayed, except for X639. The highest concentration of toxic ions in leaves was detected in Carrizo citrange and US897 for Cl⁻, while the lowest concentration of Na⁺ was obtained in X639. These results provide growers with information about the sensitivity to salinity of different citrus rootstocks.

The genus Citrus amounts to one of the most relevant fruit crops in the world. This work assays overall fruit quality information in order to ascertain the optimal harvest timing of three late-season orange cultivars (‘Barberina’, ‘Valencia Midknight’ and ‘Valencia Delta Seedless’) during two consecutive growing seasons. Thus, morphological and physicochemical parameters, organic acids, polyphenolic content and antioxidant activity (ABTS and DPPH) were analyzed. ‘Barberina’ yielded the highest morphological (large and heavy fruits, albeit with lower fruit color index) and physicochemical (high juice content and intermediate but optimal acidity) fruit quality, with April providing the optimal harvest timing. By contrast, ‘Valencia Delta Seedless’ offered the smallest fruits, while ‘Valencia Midknight’ reported the lowest physicochemical juice quality (low juice content and earlier sensory depreciation). Nevertheless, both ‘Valencia Delta Seedless’ and ‘Valencia Midknight’ had higher functional quality than ‘Barberina’, which could be interesting for the industry in terms of obtaining higher added value products. Thus, ‘Valencia Midknight’ fruits recorded the highest organic acids concentration, especially in citric acid, while ‘Valencia Delta Seedless’ fruits showed the highest antioxidant activity and ascorbic acid concentration. In addition, while March-April emerged as the optimal harvest timing in terms of the highest organic acids concentration and antioxidant activity, it was February the optimal harvest timing for polyphenols content. Finally, the 2017/2018 growing season proposed better response of color index, density, polyphenols and antioxidants, but lower results of total organic acids.