Saeed Ghanbari Zarmehri - Department of plant product, agriculture management of Mahvelat, Khorasan Razavi, Iran
Hadi Sareban - Ph.D candidate, Department of agriculture, Islamic Azad university Gonabad branch, Iran
Akram Heydari - Department of plant product, agriculture management of Mahvelat, Khorasan Razavi, Iran

Pistachio (Pistacia vera L.) is an important commercial nut in Iran which was adapted to the native climate. However, the climate change caused to warming winter recently in Iran. Determination of chilling requirement for pistachio trees helps to the researchers to identify the challenge of inadequate winter chilling in the warm winter condition. This experiment was conducted to determine chilling requirement for bud breaking in pistachio cv. Badamie Sefide Mahvelat as an adapted cultivar in Khorasan Razavi province and cv. Akbari. The branches with enough flower buds were taken from pistachio trees during November 2017 when the minimum and maximum temperatures reached to 7.9 °C and 18.2°C respectively. Cuttings with flower buds were kept under (5±1) °C for 0, 600, 800, 900, 1000, 1200 and 1300 h, respectively and were placed on green house under white light at (22±1) °C condition. Each treatment included 15 replications and study was carried out in completely randomized design. The results indicated that pistachio cv. Badamie Sefide Mahvelat needs a chilling period between 1000-1200 h. Additionally, floral bud breaking occurred homogeneously and it process followed a uniform subordinate in 1000 h and 1200 h treatments. Chilling requirement of cv. Akbari was determined between 1200-1300h.

chilling requirement, climate change, cv. Badamie Sefide Mahvelat, Pistachio