Influence of Deficit Irrigation in Phase III of Fruit Growth on Final Fruit Quality in Sweet Orange 'Lane Late'

摘要

The citrus crop in Spain is mainly directed to fresh fruit production. The needs of the international market mean that it is necessary to delay the harvesting of some later varieties of mandarin and sweet orange. The climatic condition in the south-east of Spain make it difficult for this later citrus fruit production since the climatic conditions reduce the acid content. It is well known that deficit irrigation increases soluble solids and acid content in citrus fruit. The aim of this work was to apply a strategy of deficit irrigation to improve the final fruit quality in 10-year-old ' Lane late' sweet orange grafted on Carrizo citrange (Citrus sinensis L. Osb.×Poncirus trifoliatta L. ). The experiment was carried out over two years in an experimental orchard located in Torre Pacheco (Murcia, south-east Spain). The deficit irrigation (DI) treatment consisted of the suppression of irrigation in phase III of fruit growth (1st October to 28th February). The irrigation cut-off in phase III reduced the midday stem water potential (ψmd) , the plant water status being heavily influenced by rainfall. In both of the two years, the DI treatment did not alter fruit yield although average fruit weight was slightly reduced. The main effects of DI was on the final fruit quality, increased total soluble solids (TSS) and titratable acidity (TA) and decreased juice percentage, without altering the final maturity index. Plant water stress integral (Sψ) was correlated positively with TSS and TA and negatively with juice percentage. In conclusion, a DI strategy could be useful for improving the final content of TSS and the TA, therefore allowing the harvest to be delayed in this region.