A field study was carried out under rainfed conditions during the growing season 2008/2009 in Maru (Northern Jordan) to evaluate the phenological variation using heat-accumulated system and its relation with yield in sixteen durum wheat genotypes. Grain yield was negatively correlated with growing degree days (GDDs) to maturity, while positively correlated with GDD to heading. Increasing GDD to heading resulted in higher grain yield, while increasing grain fill duration had little effect. Rapid

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... grain fill rate was positively correlated with grain weight and negatively correlated with grain fill duration. Waha-1, Omrabi-5, and Massara-1 genotypes had the highest grain yields among genotypes studied. These three genotypes tended to have relatively longer preheading periods with early maturity. The results of this study indicate that Mediterranean-adapted cultivars would have long preheading periods, followed by short periods and high rates of grain fill and mature early to avoid late-season drought and high-temperature stress and to attain high yields. Therefore, it is recommended for the development of high yielding wheat cultivars adapted to semiarid environments to select the genotypes with early maturity and a relatively long time to heading.