Dragana DrobnjakFaculty of Applied Ecology - Futura, Belgrade, Serbia

Abstract

The effect of plant growth regulator in early stages of fruit development is to slow or stop the growth of lateral fruits and to cause their early drop. Two commercial plant growth regulator formulations naphthalene-acetamide (NAD) and naphthaleneaceticacid (NAA) were used. The applied doses of plant growth regulator were in accordance with the manufacturer's recommendations, for Amidthin 100-130 g/hl and Nokad 20-25 ml/hl. The first treatment was applied after full bloom, and the second when central fruit was 9-12 mm in size. The biggest effect on fruit weight and size was recorded on treated Golden Delicious fruits grafted on M 9 rootstock. It was found that minimum number of fruits per branch was on M 9 rootstock. Also, the most pronounced effect of fruit thinning regarding fruit weight and size was on trees grafted on M 9. Results showed that fruits had decreased firmness and increased dry matter content. However, it did not show significant differences in values of iodine - starch test and acid content.