The combination of dwarfing genes Rht4 and Rht8 reduced plant height, improved yield traits of rainfed bread wheat (Triticum aestivum L.)

The utilization of dwarfing genes in wheat breeding has reduced plant height, improved lodging resistance and increased the harvest index. The effects of dwarf genes Rht4 and Rht4 + Rht8 on early vigor, morphology and grain yield traits in bread wheat were evaluated using the F4, F5 and F6 dwarf lines derived from Chinese wheat cultivars Xifeng20 and Jinmai47 (with Rht8) with Burt ert 937 (Rht4 donor) in three crop seasons under rainfed conditions. The results showed that Rht4 did not affect coleoptile length but increased maximum length, total length and surface area of roots, while root diameter was reduced. Compared with their tall parents, plant height was reduced by 8.8-15.3% and 7.4-17.7% in the Rht4 and Rht4 + Rht8 dwarf lines, respectively. The length and diameter of the internodes other than the peduncle was significantly reduced. The length, width and area of flag leaf were not affected in the Rht4 + Rht8 dwarf lines but were increased in the Rht4 dwarf lines. Grain number per spike was reduced in the Rht4 and Rht4 + Rht8 dwarf lines. Finally, the 1000-kernal weight, aboveground biomass and grain yield were also reduced in the Rht4 dwarf lines, while they were increased in the Rht4 + Rht8 dwarf lines. These results revealed that the dwarfing gene Rht4 had moderate effects on plant height and the combinations of Rht4 and Rht8 could reduce plant height to a desirable level and improve yield-related traits in the rainfed cultivation.