Studying the Genetic Gain of Traits Related to Remobilization and Photosynthesis in Bread Wheat Cultivars Released During Five Decades in Golestan Province of Iran

In order to determine the trend of breeding progress and the genetic gain in the Iran's Golestan province, twenty registered spring wheat cultivars, which had been widely cultivated from 1968 to 2018, were investigated. A randomized complete block design with three replications was conducted to study these cultivars in the research stations of Gorgan and Gonbad during three consecutive years (2015-2018). Different morphological characteristics, grain yield and yield components, and some important traits related to remobilization and photosynthesis were measured. Morphological traits including plant height, peduncle length, and spike length did not show any significant trend during the 50-year of breeding improvement in these regions; whereas significant increases were observed for grain yield, biological yield, harvest index, thousand kernel weight, and grain filling rate in the both areas. During the period of breeding investigated, the total contribution of remobilization has decreased, in particular that from stem’s, showed a significant decrease. In contrast, the amount, efficiency, and contribution of photosynthesis revealed to play a significant role in genetic improvement obtained for the cultivars’ successful performances in the regions. Based on the results obtained from the study of different parts of the plants, in addition to being an important photosynthetic source for wheat, over the time, as compared to the other wheat organs, spike showed an increasing potential for the amount of remobilization. It is expected that genotypes selected for higher levels of remobilization abilities with increased photosynthesis, could result in breeding superior high-yielding cultivars in future of the national wheat programs.