The effects of preharvest gibberellic acid applications to fruit drop and quality during on-tree storage of valencia orange

In our country, orange has an an important position among citrus because of increasing amount of production and demand of export. Valencia orange is suitable for late-harvested, fresh market and industry. For this purpose, it has a wide production areas. However, fruits are harvested in the late season on-tree storage due to problems of export some years and the demand for high-priced sales. In this case, fruits drop and take place quality losses. The plant growth regulators are used as solving to this problem. Valencia orange, in order to reduce fruit drop and loss of quality happened throughout on-tree storage, 10 or 20 ppm gibberellic acid (GA3) spray to trees one and two times in periods before peel color break and peel color break. Fruits were harvested from april to august by one mounth interval. Fruit drop ratio was determined and quality analysis were carried out in each term. In the experiment, it was seen that two times 10 ppm GA3 applications namely before peel color break and peel color break were reduced fruit drop and delayed color development. Consequently, it has been thought that Valencia Late orange can enable on-tree storage until the end of august to reduce fruit drop percentage, delay peel color development and protect fruit quality. Key words: Valencia Late orange, GA3, on-tree storage, quality