Yield Components and Grain Yield Responses of Four Wheat Cultivars to Growth Retardant Cycocel under Terminal Drought Stress Conditions

This research was carried out to study the grain yield, yield components and NDVI (normalized difference vegetation index) responses of four wheat cultivars to growth retardant cycocel under terminal drought stress conditions. The experiment was laid out as a split split plot with three replicates at the experimental farm of the School of Agriculture, Shiraz University, Shiraz, Iran in 2016-2017 and 2017-2018 growing seasons. The treatments consisted of two levels of water stress (full irrigation and irrigation cut off at the beginning of flowering), exogenous cycocel in two levels (4 g ha - 1 and 0) and four wheat cultivars (Sirvan, Baharan, Varedati and Ofogh). Water stress reduced the measured traits including, grain number per ear (19%), 1000-grain weight (14%), biological yield (22%), grain yield (29%), and NDVI (17%). Exogenously-applied cycocel compensated for some of such reductions including, number of spikes per square meter (18%) , grain number per ear (29%), 1000-grain weight (6%), biological yield (11%), grain yield (17%), and NDVI (5%). Ofogh and Sirvan cultivars showed a better response for most of the measured traits to water stress conditions when cyclocel was used. Regarding the ameliorating role of cycocel in reducing negative impacts of terminal water stress, application of this growth regulator could be recommended for similar conditions.