Pistachio Production Management in Iran by Rest-breaking Treatment and Comparison of Dynamic vs Chill Hour Model for Chill Accumulation

Shortage of winter chill has reduced pistachio (Pistacia vera L.) fruit yield and quality from 2015 to 2018 in Iran. In this study accumulated chilling was determined by the chill hour (CH) and the dynamic (DM) model in five regions near Shahrebabak County, Kerman Province, Iran, for dormant season 2017–2018. The CH model has been routinely used in Iran for reporting chilling accumulation for pistachios. This study suggested that the DM better differentiated regional chill accumulations, the impact of chilling on phenological indices of growth and production between cultivars ‘Owhadi’ and ‘Akbari’, with and without rest-breaking (RB) treatments of Volk dormant oil. Volk oil treatment significantly improved vegetative and reproductive development, offset lack of chilling effects on pollination and nut filling, and may have advanced budbreak in some instances.