Genetic effect of dwarfing gene Rht13 compared with Rht-D1b on plant height and some agronomic traits in common wheat (Triticum aestivum L.)

Abstract

GA-insensitive (GAI) dwarfing genes Rht-B1b and Rht-D1b have been widely used to reduce plant height, increase yield and improve harvest index, but they also express shorter coleoptiles and poor seedling vigor. GA-responsive dwarfing genes, such as Rht13 have potential for wheat improvement since they may not be associated with the latter effects. In this study, the effects of dwarfing genes Rht-D1b and Rht13 on plant height, coleoptile length, seedling root characters and yield components were investigated and compared in field environments in northwest China, using F2:3 and F3:4 lines derived from a cross between the Chinese winter wheat Xinong223 (Rht-D1b) and Magnif M1 (Rht13). The results showed that both Rht13 and Rht-D1b significantly reduced internode length and plant height. GA-responsive (GAR) dwarfing gene Rht13 reduced plant height by 16.5%, but did not affect coleoptile length or seedling root characters. Rht13 lines demonstrated better seedling vigor with greater potential for seedling establishment in the field. The GAI dwarfing gene Rht-D1b was associated with shorter plant height (22.0% in general) along with shorter coleoptile length, shorter total root length, smaller root surface area, and less root volume. These phenotypes may contribute to lower seedling vigor and poorer seedling emergence in the field. The GAR dwarfing gene Rht13 could compensate for some of the negative effect of the GAI dwarfing gene Rht-D1b on root surface area and root volume, which could benefit the root system. The combination of these two dwarfing genes produced even shorter plants (40.3% in general) and resulted in the shortest distance from spike to flag-leaf ligule. Rht-D1b did not affect the diameter of stems and flag leaf size adversely, while Rht13 narrowed the diameter of stems (except the peduncle) and narrowed flag leaf width. Grain number spike−1 and number of fertile tillers plant−1 was similar between lines with single dwarfing gene (Rht-D1b or Rht13) and tall lines, but less grain number spike−1 was observed in lines with double dwarfing genes. 1000-kernel weight was significantly reduced by Rht13, while Rht-D1b had no significant effect on 1000-kernel weight. In the rainfed winter wheat environments encountered here, Rht13 and Rht-D1b reduced biomass plant−1 by 24.5% and 19.9% and grain yield plant−1 by 25.8% and 25.7%, respectively, but harvest index remained the same as tall lines in both Rht13 and Rht-D1b dwarf lines.