The interactions of Rht15 and Rht1 alleviate some of their negative effects on agronomic traits in durum wheat

The application of dwarfing genes in wheat breeding effectively reduced plant height, improved lodging resistance and increased the harvest index. Although the gibberellin-responsive (GAR) dwarf gene Rht15 did not negatively affect coleoptile length or root traits while reducing the plant height, it reduced the yield plant−1. The gibberellin-insensitive (GAI) dwarf gene Rht1 can increase wheat yield under favorable conditions, but it reduces coleoptile length and affects root traits. This study was conducted to investigate whether the interaction of Rht15 and Rht1 can alleviate their negative effects. To analyze the interaction of Rht15 and Rht1, field experiments were conducted with the F5, F6 and F7 lines of the four genotypes, Rht15+Rht1, Rht15, Rht1 and tall lines detected using Rht15 and Rht1 molecular markers, derived from Durox (Rht15) and Kronos (Rht1), by comparing their effects on seedling traits, plant height and internode length, lodging resistance, flag leaf, yield and quality traits in durum wheat. The results showed that although the interaction of Rht15 and Rht1 did not overcome the inhibitory effect of Rht1 on coleoptile growth, it alleviated the negative effect of Rht1 on maximum root length (+14.8%). The grain yield plant−1 (+7.2%) of the Rht15 lines was improved under the action of Rht1 but was still lower than that of the Rht1 lines (−12.7%). The Rht15+Rht1 lines had the strongest effect on reducing plant height and center of gravity height (−42.2% and −41.5%), which significantly improved lodging resistance (+175%). The flag leaf area (+97.4%) and SPAD value (+11.6%, +9.6% and +10.6%) were also significantly increased. In addition, the coleoptile length of the Rht15 lines was not significantly different from that of the tall lines, the plant height and center of gravity height were significantly reduced (−30.5% and −34.0%), and the lodging resistance was significantly increased (+176.8%). The Rht1 lines had increased grain yield (+12.7%) due to an increased 1000-kernel weight (+12.9%) compared to the tall lines. In conclusion, the combination of Rht15 and Rht1 alleles enhanced the advantages and partially alleviated the defects in some traits when compared to the individual alleles, but the grain yield plant−1 was still lower than the Rht1 lines. This reflected the limitations of Rht15, and further confirmed the yield advantages of Rht1. •Rht15 and Rht1 interacted to partially alleviate each other's defects in some traits.•Rht15 allev