INFLUENCE OF GIRDLING AND FOLIAR-APPLIED UREA ON APPLE (MALUS DOMESTICA L.) FRUIT QUALITY

Abstract

The influence of four rates of foliar-applied urea (0, 0.2, 0.5 and 0.8%; i.e., N0, N1, N2 and N3 rates, respectively) without or with girdling was evaluated on ‘Fuji’ apple fruit quality parameters and activities of two key enzymes in aroma metabolism. Girdling treatment at a given rate of foliar-applied urea increased fruit weight, size, contents of soluble sugars (SSC), vitamin C (VCC) and total amino acids (TAAC), while decreased soluble protein content (SPC), and titratable acidity (TAC) as well as activities of alcohol acyltransferase (AAT) and alcohol dehydrogenase (ADH). With the increasing rates of foliar-applied urea regardless of girdling treatments, increased SPC, VCC, TAAC, and TAC as well as AAT activity, while decreased SSC. The combination of girdling and urea application increased fruit size and weight, VCC and TAAC. Favorable fruit quality responses were obtained at 0.5% urea rate. This study demonstrated that combined application of girdling and foliar spray of urea improved most of fruit quality parameters.