Combined Effect of CPPU Application and Fruit Thinning on the Size and Quality of Hardy Kiwifruit

The effect of simultaneous treatment of N-1-(2-chloro-4-pyridyl)-N-3-phenylurea (CPPU) application and fruit thinning on fruit size and quality of A. arguta was studied. Mature vines of A. arguta (Sieb. et Zucc.) Planch. ex Miq., 'Mitsuko', grown at Kagawa Agricultural Experiment Station were used. Six treatments were used: CPPU 0 ppm + the fruit numbers per one shoot (6, 12, and 24) and CPPU 5 ppm + the fruit numbers (6, 12, and 24). Fruit thinning was done by hand and CPPU was applied at 10 days after petal fall. Fruit growth was measured until harvest. Fruit harvested on August 29 were treated with 500 ppm ethylene for 48h at 20 degrees C and the quality was examined. In all the treatments, fruit growth was characterized by a double sigmoid curve. CPPU treatment and fruit thinning markedly enhanced the initial fruit growth, especially in the longitudinal direction. The largest fruit (13.2 g) was obtained by the treatment of 6 fruits + CPPU, while the average fruit weight was 4.7 g in 24 fruits without CPPU treatment. Highest soluble solids concentrations (SSC)/titratable acids (TA) ratio was recorded in 6 fruit + CPPU treatment. Reduction of TA and ascorbic acid contents was observed in the largest fruit induced by the severe fruit thinning with CPPU treatment.