Determination of chilling and heat requirements of grape cuttings and changes in carbohydrates and hormones during chilling period

This research was carried out to determine the chilling and heat requirements of grapevine cultivars(Rotabi, Siah Shiraz and Yaguti) and carbohydrate and hormones changes in chilled cuttings. Uniform cuttings of above mentioned cultivars were harvested when leaves were abscised in autumn, and then transferred to refrigerator (2˚C). Cuttingswere subjected to 0 (unchilled control), 100, 200, 300, 400, 500 chilling hours, then cuttings were put in distilled water at room temperature and continues light conditions. Results indicated that the highest bud break percent of ‘Siah Shiraz’, ‘Rotaby’ and ‘Yaguti’ were obtained from 500, 400 and 400 h respectively. The shortest time (29d) to 50% bud break of ‘Siah Shiraz’ was in 500 h(29 d), in ‘Rotabi’ and ‘Yaguti’ were in 400 h (20 and 16d) chilling. Rate of starch content in all cultivars were decreased when chilling exposed hours increased, while soluble carbohydrate content in cuttings increased with increasing chilling hours. Also, with increasing chilling exposed hours, GA, Cytokinin and Auxin contents increased whereas ABA decreased. In conclusion, chilling requirement of ‘Yaguti’, ‘Rotabi’ and‘Siah Shiraz’cultivars were 400, 400, 500 hours and heat requirements were 4320, 5472 and 8064 GDH, respectively.