Assessment of Growing Degree-Days Values of Phenological Stages in Iranian Bread Wheat Cultivars and Landraces

Growing degree-days (GDD) is considered as an alternative indicator for counting calendar days in studying of crop phenology stages. In the current study, genetic diversity of 86 Iranian wheat cultivars and 184 landraces were investiagted based on the phenological stages (day to booting, day to flowering, day to maturity and GDD of these stages) along with grain filling period, thousand grain weight and grain yield during 2013-2014 growing seasons in augmented design with 3 control cultivars (Azar, Navid and Pishtaz) in 6 incomplete blocks in Agronomy and Plant Breeding research filed, University of Tehran. The results illustrated that there is a significant difference between cultivars and landraces, so that the cultivars had higher yield and less grain filling period than the landraces. On the other hand, the results indicated that the genotypes with different growth habits have a significant difference in terms of most of the phenological traits which it could be useful either in directly or indirectly selection for increasing the length of the grain filling period along with grain yield. Since the diversity of phenological traits were higher in landraces, they can be a valuable source for selection to improving these traits. Finally, due to the importance of the phenological stages and GDD index, it is recommended that these traits also consider as well as yield and yield components in order to obtain more accurate results.