Influence of CPPU on carbohydrate accumulation and metabolism in fruits of Actinidia deliciosa (A. Chev.)

A trial was carried out to evaluate the influence of N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU), a diphenylurea derivative cytokinin,- on kiwi productivity, on carbohydrate accumulation and metabolism and on post-harvest fruit performance. CPPU (20 ppm) was sprayed on fruitlets inside the canopy 2 weeks after full bloom (AFB). CPPU influenced fruit growth soon after treatment and, at harvest, treated fruit weight and, consequently, yield per vine were about 25% higher than the control. During fruit-growth, soluble sugars (glucose, fructose and sucrose) were higher in treated fruits than in the control ones, In the first period of fruit development glucose was the most abundant carbohydrate and CPPU treatment increased the fruit glucose content significantly. During the period of starch accumulation, treated fruits showed a higher starch content and a higher ADP-glucose pyrophosphorylase activity, Starch accumulation started earlier in treated fruits than in the control ones. At the end of the growing season the degradation of search in treated fruits started earlier and/or was faster than in the control ones, so that at harvest treated and control fruits contained the same amount of starch. As a consequence, treated fruits at harvest had higher contents of soluble sugars. This indicates that CPPU induced faster and/or advanced fruit ripening. The chlorophyll content was higher in CPPU treated fruits. During storage, the differences in carbohydrate content disappeared and treated fruits performed as well as control ones, maintaining good quality for up to 6 months.