Abstract: 【Objective】 Zhongmai 175 is a widely adapted and largely planted winter wheat cultivar both in irrigated areas of northern winter wheat zone and rainfed areas of Huang-Huai Rivers Valley wheat zone. Therefore, understanding its dry matter accumulation and water use performance could be helpful to reveal water saving and high-yielding mechanism of wheat.【Method】Field experiments were conducted in Wuqiao of Hebei province and in Shunyi of Beijing with two wheat cultivars (namely, Zhongmai 175 and Jingdong 17) under three limited irrigation levels, including no irrigation in whole growing stage (W0), irrigation in jointing stage (W1, 75 mm), and irrigations in jointing and flowering stage (W2, 75 mm +75 mm). Phenotypic traits such as population vitality, dry matter accumulation and distribution, yield and water use efficiency (WUE) were compared to understand the differences between the two cultivars as well as their responses to different irrigation levels.【Result】The highest yields were obtained under W2 treatment for both cultivars, while yield decreased with the reduction of irrigation. The W0 treatment mainly reduced the kernel number per square meter due to the remarkable decrease of 47-67 in spike number per square meter (SN) and 1.6-5.1 decrease in kernel number per spike (KNS). The W1 treatment mainly reduced the thousand-kernel weight (TKW) about 0.6-1.5 g. Water deficit notably reduced evapotranspiration (ET) and population biomass. Nevertheless, it remarkably increased the translocation amount (TA) of dry matter accumulated before flowering to grains. However, moderate water deficit (W1) increased the WUE of both cultivars. Compared with Jingdong 17, Zhongmai 175 showed higher yield and yield stability under different irrigation treatments. In Zhongmai 175, most of the physiological traits like normalized difference vegetation index (NDVI), canopy temperature depression (CTD) and content of conserved water-soluble carbohydrates (WSC) in stem in middle grain-filling stage were higher; contrastingly, water sensitive coefficient (WS) of most yield traits was lower in Zhongmai 175. These characters might be the physiological basis for the high yield and efficiency of Zhongmai 175. The WS of KNS and biomass showed close correlation with WS of yield, as well as WS of NDVI and CTD in early stage of grain-filling.【Conclusion】The rapid accumulation of dry matter in early stage, large pool capacity and strong ability of population vitality might be the main reasons for the water-saving and high yield of Zhongmai 175. The differences of NDVI and CTD in early stage of grain-filling under different irrigation treatments could be used as fast and comprehensive evaluation parameters in detecting water sensitivity of different cultivars.

Key words: winter wheat, water use efficiency, water sensitive coefficient, content of conserved water-soluble carbohydrates, yield