Variation in Developmental Stages and its Relationships with Yield and Yield Components of Bread Wheat Cultivars Under Field Conditions: II- Yield and Its Components

To study the variation in developmental stages and its relationship with grain yield and its components, this reasecrh was conducted in three successive cropping seasons (2000 – 2003) in experimental field stations of Seed and plant Improvement Institute, Karaj, Iran. Twenty bread wheat cultivars adapted to four different agro-climatic zones (Cold and Tempearte Cold Tempearte Southern Warm Dry and Northern Warm and Humid) were studied-using randomized complete block design with three replications under field conditions in Karaj, Iran. Results revealed that bread wheat cultivars were significantly different in term of bilological yield, grain yield and yield comonents. These variations could be aattributed with genetic differences and adaptation to different agro-climatic zones as well as variation in their phonology particularly duration of differnt developmental stages. Cultivars adapted to cold and tempearte cold and temperate zones produced greater biological yield (17798 and 17662 Kg ha-1, respectively), and grain yield (7236 and 7229 kg ha-1, respectively). There was not considerable differences among different groups of cultivars for HI (39.3–42.5%). Results of correlation analysis between grain yield and its components with different phonological developmental stages also indicated that relationship between spike No. m-2 and was positively correlated with with the duration from Sowing to Terminal Spikelet stage, however, it was negatively associated with duration of rapid stem elongation (Terminal Spikelet to Anthesis) stage. The relationship between 1000 grain weight (TGW) and the duration of vegetative (Sowing to Double ridge) and pre-anthesis reproductive (Sowing to Anthesis) stages was also negative. It is concluded that studies of phonological development variations and its relationship with grain yield and yield components over years and locations can be used to expalain, to graet extent, the the adaption of different bread wheat cultivars to different agro-climatic conditions as well as variation in their grain yield.