Strong Source and Fluent Flow May Increase Grain Weight and Yield in Water‐Saving and Drought‐Resistance Rice: A 5‐Year Field Study

ABSTRACT Water‐saving and drought‐resistance rice (WDR) is a new type of cultivated rice, which not only has the characteristics of high yield and quality of rice, but also has the properties of water‐saving and drought‐resistance of upland rice. However, the source, flow and sink basis of its high yield were still unclear. It was of great significance for the breeding of high‐yielding WDR varieties and cultivation regulation to clarify the characteristics of the source, flow, and sink of WDR yield formation and its regulation effects. In this study, WDR varieties (more than 20) with three groups of different grain weight types: small grain weight type (SGWT, grain weight < 22.5 mg), medium grain weight type (MGWT, 22.5 mg < grain weight < 25 mg) and large grain weight type (LGWT, grain weight > 25 mg), were selected as materials. The contribution of grain weight to the yield, the changes of source (flag leaf length and width), flow (stem length and diameter), and sink (grain length and width) and the regulation effects of grain fertiliser application rate (GFAR) on grain weight in WDR were studied through a 5‐year field cultivation. The results showed that (1) the average yield of LGWT was significantly higher than that of SGWT and MGWT varieties, with an increase of 5.23%–9.88% and 2.06%–3.08%, respectively. Larger grain weight was the primary feature of high‐yielding WDR varieties. (2) There was a significant positive correlation between grain weight and, flag leaf width (source) and stem diameter (flow) at the middle grain filling stage (25 days after heading) ( r = 0.467*–0.688**). (3) Compared with no GFAR treatment, the applying GFAR treatments (GFAR at 25 and 50 kg ha −1 ) increased the stem diameter, flag leaf width, grain weight and yield of Huhan1505 (SGWT), Huhan1517 (MGWT) and Hanyou756 (LGWT) to varying degrees, and the increase of SGWT was greater. Larger flag leaf width (strong source) and wider stem diameter (fluent flow) were material foundation for high yield of WDR. Promoting source strength and smooth flow at the middle grain filling stage was conducive to promoting the increase of grain weight and yield of WDR.