Evaluation of heat terminal stress effect on yield and yield component of bread wheat cultivars in Moghan

Heat stress during the seed filling period is one of the main obstacles for crop production in warm areas of IRAN. Selecting the suitable sowing dates, use of high potential and tolerant cultivars for crop production in heat stress conditions are necessary. In order to evaluate the effect of heat stress on yield, yield component, and morpho-phonological traits of wheat, an experiment was conducted in agriculture and environmental research center of Ardebil (Moghan), Iran in 2015-2016. The experimental design was split block design in randomized complete block design with three replications. The experimental factors were sowing dates (5 Nov, 20 Nov, 5 Dec and 20 Dec) in main plots and 15 wheat cultivars ( Shirodi, Darya, Morvarid, Chamran, Gonbad, N-87-20, N-80-19, Kohdasht, Zagros, Karim, Pishgam, Mihan, Orom, Arta and Zare) in subplots. The results showed that the effect of planting date and cultivars was significant on most of the traits evaluated. The grain yield (kg/h) in timely sowing date did not lead to late planting dates. This is due to plant lodging in early planting dates and coinciding the time of flowering and seed formation with the occurrence of disease in the region. When the plant grain yield per area and main stem was evaluated, it was found that the delay in sowing date, had reduced the grain yield per plant and grain yield in main stem. Karim, Arta and Chamran cultivars, in terms of grain yield per plant in early and late planting dates were superior to other cultivars. In terms of grain yield per plant in early and late planting dates were superior to other varieties. With delay in planting date, plant biomass yield and straw yield per plant was reduced. The maximum grains number per spike was related to first planting date (50/4). The lowest number of grains per spike was observed in the fourth planting date. The number of days to heading and pollination in the third and fourth sowing date was less than the first and second planting dates. The relationship between the various traits individually in the different sowing dates were evaluated through correlation analysis generally showed positive and significant relationship between the number of grains per spike and grain yield were observed. There was not a strong correlation between seed weight and seed yield. How correlation between the phonological characteristics and agronomic traits in the different sowing dates was different, that shows correlation of these traits are variable depending on weather conditions.