Deficit irrigation and maturation stage influence quality and flavonoid composition of ‘Valencia’ orange fruit

BACKGROUND:Effects of continuous deficit irrigation (DI) and partial rootzone drying (PRD) treatments (50%ETc) in comparisonwith full irrigation (CI, 100% ETc) were investigated during ‘Valencia’ orange fruit maturation. Ultra-high-performance liquidchromatography/high-resolutionmass spectrometry was used to quantify hesperidin, narirutin, tangeritin, nobiletin, didyminand neoeriocitrin in the fruit juice and peel.RESULTS: No significant effect of irrigation was found on yield, juice soluble solids or acidity. Juice color was not influencedby irrigation or harvest date, whereas peel color increased during maturation and was more pronounced in CI and PRD fruits.Juice acidity reached a peak in May, while soluble solids increased linearly throughout maturation. Hesperidin was the majorflavanone detected during maturation, with concentrations 200-fold higher in the fruit peel than in the juice. In the peel,narirutin, didymin and neoeriocitrin decreased while hesperidin, nobiletin and tangeritin increased with maturation. Narirutinsynthesis in the orange fruit was insensitive to irrigation strategy. In fruit peels, PRD and DI induced the decline of hesperidin,nobiletin and tangeritin only in June, whereas in the juice, deficit irrigation treatments induced an increase in hesperidin anddidymin.CONCLUSION: These results suggest that deficit irrigation, in particular the conditions imposed with PRD, may cause asignificant accumulation shift of total flavonoids from the fruit peel into the juice, with a positive impact on juice quality andnutritional value. Fruit compositional changes during maturation also suggest that late harvest can improve fruit palatabilityand nutritional quality under the cultural and environmental conditions of this study.