Supplemental irrigation (SI) is the primary strategy to reduce the adverse effects of drought stress on rainfed wheat growth and grain yield in the Mediterranean region. The study aimed to evaluate the effects of SI at critical growth stages on traits related to dry matter (DM) accumulation and remobilization, N utilization efficiency in various cultivars. Two field experiments with four irrigation levels (I0 = rainfed, I1 = SI at booting stage, I2 = SI at booting and anthesis stages, I3 = SI at booting, anthesis, and grain filling stages) and five cultivars (Rejaw, Sardari, Homa, Azar2, and Sirwan) was conducted during the 2015–2016 and 2016–2017 wheat growing seasons. The average higher precipitation in the first growing seasons increased the DM accumulation in vegetative organs, grain yield, and N use efficiency (NUE). The effect of SI on the DM accumulation in crop components at anthesis and post anthesis, crop components DM remobilization (DMR), crop components DMR contribution to grain and DMRE, grain yield, N utilization efficiency (NutilE), N harvest index (NHI), NUE, and grain protein concentration (GPC) in wheat cultivars was assessed. Results showed that overall SI increased DM accumulation at anthesis and post anthesis, DMR, grain yield, NutilE, and NUE in cultivars. SI at anthesis and grain filling stages decreased DMRE, NHI, and GPC. The difference between cultivars was evident in studied traits, and in general, the Sirwan cultivar had more DM accumulation at anthesis and post anthesis and eventually higher grain yield than other cultivars. SI reduced the dependence of the plant on DMR for grain filling so that the DMR contribution to grain yield decreased from 76.79% in rainfed conditions to 62.44% in three times SI (I3) conditions.
