Rootstock-modulated yield performance, fruit maturation and phytochemical quality of 'Lane Late' and 'Delta' sweet orange

Graft combinations of sweet orange cultivars Delta and Lane Late on six rootstocks were established on calcareous clayey soil and evaluated for compatibility, yield, and fruit physicochemical quality attributes at three stages of harvest maturity. Citrumelo proved a deleterious rootstock to both scions, while GouTou was deleterious to Delta and had low compatibility with Lane Late. Most compatible rootstock for Delta was Sour Orange, whereas all rootstocks except GouTou were equally compatible with Lane Late. Yield and fruit weight were highest on Volkameriana. Titratable acidity was highest on Sour Orange and Carrizo and lowest on Volkameriana. Dominant acids were citric (8.5-11.3 g/L), malic (1.8-1.9 g/L) and succinic (1.3-1.4 g/L). Citrate/malate ratio was lower in Lane Late and declined further with maturation. Acids were highest on Sour Orange and Carrizo. Increased levels of malate (2.07-2.21 g/L) elicited by Volkameriana may constitute an index of inferior sensory quality. Soluble solids were highest on Sour Orange, Carrizo and Cleopatra (9.6-10.6%) and lowest on Volkameriana (9.3-9.7%). Sucrose was the most abundant soluble carbohydrate (33.9-39.9 g/L) and sugar ratios were stable across rootstocks, however sucrose concentration in Delta increased with maturity at the expense of glucose and fructose. Increase in chroma paralleled increase in soluble solids during maturation of Delta but not Lane Late. Fruit phenolics were highest with the least compatible GouTou and lowest with the highly productive Volkameriana. Maximal ascorbate levels were attained at mid-maturity (380.4-450.2 mg/L) and were lowest on Volkameriana (323.4-398.8 mg/L). Considering its overall performance and resistance to Citrus Tristeza Virus, Carrizo appears as a promising rootstock alternative to Sour Orange particularly on calcareous soils.