Regulated Deficit Irrigation May Alter Apple Maturity, Quality, and Storage Life

Delicious' apple (Malus domestica Borkh.) trees received regulated deficit irri- gation (RDI) early in the growing season to determine if fruit quality and storage life would he altered compared to well-watered trees. Soil moisture and leaf water potential were lower in RDI trees than in those that did not receive RDI most of the season. Internal ethylene concentration increased logarithmically earlier in RDI apples. At harvest, RDI fruit were smaller and had a higher soluble solids concentration (SSC) and lower titratable acidity. Starch degradation was delayed in RDI fruit, and their color was not affected. Firmness was not affected when the effect of size on firmness was removed. The SSC of RDI apples remained higher during storage, but starch content, titratable acidity, firmness, and color were similar. Plant water deficits and reduced wetted root volume have been studied to control the vegetative growth of commercial fruit trees (Chalmers et al., 1981; Ebel, 1991; Irving and Drost, 1987; Mitchell et al., 1984). Plant water deficits were manipulated by applying less water through irrigation than trees would have used, a method called regulated deficit irriga- tion (RDI) (Mitchell et al., 1984). Using RDI commercially to control vegetative growth requires an understanding of concomitant changes in fruit maturity, quality, and storage life. Plant water deficits during the entire cell- elongation phase of fruit growth can alter fruit quality and ethylene production (Guelfat-Reich et al., 1974). The current study was conducted to determine how RDI applied early in the cell- elongation phase of fruit growth affects fruit maturity, quality, and storage life. This study was conducted at Washington State Univ., Prosser, in south-central Wash-