Comparing the effects of GA-responsive dwarfing genes Rht13 and Rht8 on plant height and some agronomic traits in common wheat

Rht8 is the only GA-responsive dwarfing gene used in wheat grown in rainfed or irrigation-limited areas. To assess an alternative dwarfing gene, the effects of GA-responsive dwarfing gene Rht13 on plant height and some agronomic traits were compared with Rht8 in this study. The four homozygous genotypes of the F2 individuals, F2:3 and F3:4 lines derived from the cross between Jinmai47 (Rht8) and Magnif M1 (Rht13) were used to evaluate and compare the effects of Rht13 and Rht8. The coleoptile length and seedling root characteristics was conducted under laboratory conditions, while plant height and various yield components were evaluated in field environments in northwest China. Rht13 significantly shortened the length of all internodes (except the basal internode) and reduced final plant height by 30.3% (30.1 cm) on average, while Rht8 mainly reduced peduncle length alone to obtain a plant stature shortened by only 15.7% (16.0 cm). The greater effect of Rht13 on plant height resulted in the distance from spike to flag leaf ligule being decreased by 97.7%. The effect of Rht13 was even greater when combined with Rht8 (104.9%), such that the spikes failed to fully emerge from the flag leaf sheath. Compared with tall genotypes, coleoptile length and seedling root characteristics were not significantly affected by either Rht13 or Rht8, which might favor the utilization of Rht13 or Rht13 + Rht8 in rainfed and irrigation-limited areas. Fewer grains spike−1 were observed in lines with Rht13 alone (18.2%) and with both dwarfing genes (Rht13 + Rht8, 18.9%), whereas there was no significant difference between the lines with Rht8 alone and tall lines. Rht13 and Rht8 reduced biomass plant−1 by 27.9% and 25.2% and grain yield plant−1 by 29.0% and 17.4%, respectively. Rht13 did not affect 1000-kernel weight and harvest index whereas Rht8 significantly increased 1000-kernel weight and harvest index. In the rainfed winter wheat environment encountered in northwest China, Rht13 reduced grain number spike−1 significantly. This effect may be due to the very short distance from spike to flag leaf ligule. This undesirable effect may be improved through selection. If so, then there is potential for using Rht13 in wheat improvement in rainfed and irrigation-limited areas.