The effects of giberellic acid applications and gridling method on yield and quality on'horoz karasi' cultivar of grapevine

'Horoz Karası', one of grapevine cultivar in Turkey, is good for Siirt province as a table grape. In spite of high yielded and good quality, the disadvantage of variety is having very tight grape clusters. It is aimed to increase yield and quality with some practices with this thesis project. The study was conducted with 6-years-old grapevine in the experimental orchard of the University of Siirt. Four different practices, which are Gibberellic acid, Girdling method (BA), Gibberellic acid + Girdling method and Control, were applied on 'Horoz Karası' to increase yield and quality. Three different doses, 50, 80 and 120 ppm/year were applied in three different stages. Harvest of grapevine were made on 5th of August in girdling method, on 15th of August in Gibberellic acid + girdling method, on 25th of August in Gibberellic acid application only and on 22nd of August in Control. That is, girdling method provided a 20-days earliness for harvesting. Girdling method also provided high yielding with 3836 kg per decar. On the other hand, girdling method caused to tight grape clusters, which is unfavorable for table grape production. Unlike girdling method, Gibberellic acid caused cluster thinning on grape clusters. With the doses of 80 and 120 ppm, cluster thinning on clusters was risen, moreover, grapes become more ovoid and the yield was decreased. Girdling method with 50 ppm GA3 was resulted high yielding and better quality. In the case of using in Must or grapevine juice, girdling method will be better in 'Horoz Karası' cultivar. For table grape production, it is recommended to do Girdling method with 50 ppm GA3. With these practices, harvesting was made on 15th of August in Siirt province with 3771 kg/da yield, 426 g cluster weight, average cluster tightness (3.2).