Evaluation of Yield and Grain Filling Rate of Bread Wheat Promising Lines (Triticum aestivum L.) to Growth Degree Days (GDD)

Increasing wheat yield requires an understanding of appropriate management method that are Increasing wheat yield requires an understanding of appropriate management method that are most important sowing date and appropriate cultivars. Evaluation of yield and grain filling rate of bread wheat promising lines to normal and late seeding dates, this experiment was carried out at Gorgan research station during 2015-2017. The experiment was a spilt-plot based on RCBD with three replications. The main factors was two sowing date December 15th (normal seeding date) and January 15th (late seeding date) and the second factor were eight genotype and cultivar of wheat. The results of combined analysis of variance showed that the effects of year, sowing date and interaction effects of year × sowing date were significant on all of traits under study expect of harvest index. Also interaction effects of year × genotype were significant on all of traits under study expect of number of grains per spike and growth degree day to maturity. The suitability of climatic conditions during plant growth in normal seeding (December 15th) caused more tillers fertilized. On the other hand, the warmth and dryness of the air at the later seeding date reduced the number of fertilized tillers. Results showed that with delay in seeding date, mean of growth degree day to physiological maturity decreased. Also results of mean comparison of interaction effects of year × genotype and of year × sowing date showed that the genotype SAUAL/3/MILAN/S87230//BAV92 and Gonbad cultivar had higher length of filling period and rate of effective grain so produced acceptable yields compared to other.