Effect of leaf defoliation on yield and yield components of wheat cultivars under drought tension conditions

Although sink-source relation could be differed under drought tension conditions compared to optimum conditions, there are limited research with focus on this topic. In the present research, sink-source relation under drought tension conditions was investigated in a field experiment based on statistical randomized complete blocks design at College of Agriculture of Shiraz University during 2013-2014 cropping year. The treatments included irrigation regime at two levels normal irrigation and cutting off irrigation at flowering in main plots, Pishtaz, Chamran and Marvdasht wheat cultivars in sub plots and treatment of no defoliation and defoliation of all leaves except flag leaf at stem elongation and in flowering sub sub plots. The results showed that drought tension and defoliation decreased significantly ear length, grain number per ear, one-thousand grain weight, biological yield and grain yield as well as water productivity in all three cultivars. Delaying in leaf defoliation, reduced its negative impact on yield and yield components of wheat cultivars, so that defoliation at stem elongation and flowering stages was associated with 68.4 and 31.4 percent reduction in average of grain yield cultivars, respectively. Grain yield reduction in defoliation treatment at the time of stem elongation was due to reduction in grain number and in defoliation treatment at the time of flowering was due to grain weight reduction. Defoliation treatment, could compensate some losses in yield and yield components due to drought tension, in the other side, Chamran cultivar had the most tolerance to drought tension and defoliation; therefore, Chamran cultivar had better performance in such conditions. Due to higher tolerance of Chamran cultivar to drought tension and defoliation, use of this cultivar in the regions with wet limitations deserves long term explorations with more details.