Effect of Last Irrigation and Harvest Time on Fruit Quality and Freezing Tolerance of Vitis vinifera L. cv. Bidane Sefid

In vineyard where ‘Khazandeh’ training system has been employed, the last irrigation and harvest time depends on type of product usage (table grapes or raisins), product price, climatic conditions and not facing the process of raisin production in open spaces with early autumn rains. This study was carried out in 2015- 2017 to investigate the effect of last irrigation cutting-off and harvest time on freezing tolerance of Bidane Sefid grape buds and its fruit quality. The experiment was conducted in a randomized complete block design with 3 treatments and 6 replications in Khosbijan, Shazand, Iran. Treatments included the first treatment: cut-off irrigation on September 5 and harvest on September 15, the second treatment: cut-off irrigation on September 15 and harvest on September 25 (control) and the third treatment: cut-off irrigation on September 25 and harvest on September 4. After early frost in autumn of 2016 and evaluation of the sprouting percentage in the spring of the following year, its amount in second and third treatments was 19.46 and 19.31%, respectively, with a significant difference against first treatment (15.8%) but no significant difference was observed between the second and third treatments. Artificial freezing carried out on March 5 and March 10 in 2016 and tolerance to artificial freezing was evaluated based on LT50 index. The third treatment (irrigation and harvesting with delay) with a significant difference was the lowest LT50 at -7.86 ° C and has the most tolerant treatment after artificial freezing. Furthermore, the results showed TSS and pH of the fruits of the third treatment were 27.57 and 3.25, respectively, which was significantly higher than the first and second treatments. Results showed that delaying the time of the final irrigation and harvesting time improved bud cold tolerance as well as fruit quality. Therefore, contrary to public opinion, harvesting with a delay compared to the control not only increases the quality of fruits, but also increases the vine tolerance against freezing.