Dwarfing genes Rht4 and Rht-B1b affect plant height and key agronomic traits in common wheat under two water regimes

Abstract To explore the potential utilization of Rht4 in wheat improvement, we investigated and compared the effects of Rht4 and Rht-B1b on the plant height and yield components using four groups of recombinant inbred lines derived from the cross between “IDO444” (tall, no known dwarfing alleles) and “Rio Blanco” (semi-dwarf, Rht4  +  Rht-B1b ) grown under two water regimes. Rht4 , Rht-B1b and Rht4  +  Rht-B1b significantly reduced plant height by 11.5%, 19.3% and 18.2%, respectively. There were no additive effects on plant height in Rht4  +  Rht-B1b lines. Both Rht4 and Rht-B1b significantly reduced internode length and lodging score with stronger effects by Rht-B1b . Water stress affected the plant height related traits of the single Rht-B1b lines more than that of the Rht4 lines, except for distance from spike to flag leaf ligule. Grain number was increased by Rht4 and Rht-B1b , but higher spike numbers was only observed in lines with Rht-B1b . Both Rht4 and Rht-B1b significantly reduced thousand kernels weight. Rht-B1b reduced above-ground biomass but increased grain yield and harvest index, while Rht4 had less effect on these traits, compared with tall lines under both well-watered and water-stressed conditions. The Rht4  +  Rht-B1b lines produced the highest yield under both water regimes, with more grain number, greater spike number and higher harvest index. In conclusion, Rht4 did not show advantages over Rht-B1b on grain yield, but Rht4  +  Rht-B1b did, in both water regimes, which suggests that Rht4 should be combined with Rht-B1b in wheat improvement.