Evaluation of grain filling rate and duration in wheat cultivars under different supplementary irrigation regimes

The grain filling process is influenced by two important factors: grain filling rate and length of grain filling period. Grain filling rate is an attribute that can be used in selecting genotypes under drought stress conditions. The aim of this experiment was to evaluate the rate and duration of grain filling under different levels of supplementary irrigation in different wheat cultivars, in the form of split plots in a randomized complete block design with four replications. Irrigation treatments at 3 levels: no irrigation (T0, rainfed), irrigation at heading stage (T1) and irrigation at heading + early seeding (T2) in main plots and cultivar treatment including five wheat cultivars named Azar 2, Rijjaw, Sardari, Sirvan and Homa were placed in sub-plots. The results showed that the T2 treatment with an average of 1.4 mg per day had the highest and the T0 treatment with an average of 0.9 mg per day had the lowest rate of dry matter accumulation in the grain. Also, Homa cultivar with an average of 1.3 mg per day had the highest and Rijjaw cultivar with an average of 1.01 mg per day had the lowest average grain filling rate. The T2 and T0 treatments with an average of 34.6 and 30 days had a longest and shortest effective grain filling period, respectively. The results of this study showed that supplementary irrigation in dryland wheat fields can increase yield and production stability by increasing the length of grain filling period and also increasing grain filling rate.