Effect of Source Restriction and Drought Stress during Grain Growth on Grain Yield and its Components of Winter Bread Wheat Cultivars

In order to examine the effects of source restriction and drought stress on grain yield and its components of wheat cultivars, a greenhouse experiment was carried out at department of plant breading and agronomy, campus of agricultural and natural resource, Razi university in Kermanshah state in the west of Iran, during 2010-2011. The wheat cultivars were included Bahar, Parsi, Pishtaz, Pishgam, Chamran, Zarin, Sivand and Marvdasht and DN-11. The source manipulation treatments including Control (C), Defoliation of flag leaf (T1), Defoliation of all leaves except the flag leaf (T2), De-awning (T3) and Ear shaded (T4), were imposed at anthesis. Results showed that post anthesis water deficiency stress caused 18 and 22 percent reduction in grain yield and thousand grain weight in average respectively, but had no significant effect on of biomass. Zarin and Marvdasht cultivars was more sensitive to drought stress than the other cultivars. In all cultivars drought stress decreased Harvest Index at the similar level of defoliation treatments yield significantly but in Chamran decreasing rate was less than the other cultivars. The highest grain yield was observed in de-awning treatment (1.77 g spike-1) and in terms of ranking the control treatment was in the next level. In addition ear shaded treatment was the lowest grain yield (1.18 g spike-1). Also, highest thousand grain weight was observed in Control treatment (37.7 g) and lowest was investigated in the ear shaded treatment (27.2 g). Results showed that the effect defoliation of flag leaf, defoliation of all leaves except the flag leaf, de-awning and ear shaded treatmants on the grain yield due to decrease 9.3, 14.7, 4.4 and 32.9% in the well watered candition, also 13.4, 8.5, 5.8 and 27.1% in the drought stress candition. But on the thousand grain weight due to decrease 2.2, 3.9, 0.2 and 30.2% in the well watered candition and 7.1, 3.5, 2.3 and 25.2% in the drought stress candition. Current photosynthesis of spike had a significant role in grain filling formation more than flag leaf and other leaves.

wheat, drought stress, grain yield, source, flag leaf, ear, awn