Performance Story: Assessment and deployment of a new dwarfing gene in red spring wheat
Dr. Pierre Hucl, University of Saskatchewan
Breeding spring wheat varieties carrying semi-dwarfing genes is of interest, as these varieties experience less lodging, have a higher harvest index (HI), and in some cases higher grain yield and quality. The Rht18 semi-dwarf gene was back-crossed into the CWRS variety “CDC Utmost” from durum wheat and the resulting Near Isogenic Lines (NILs) were evaluated over a period of four years for potential linkage drag effects on a number of agronomic and quality traits. The short NILs were, on average, 15 cm shorter than their tall counterparts. The three stem internodes that were measured in this study, were all shorter in the short NILs. The linkage drag effects appeared to be relatively small. Lines carrying Rht18 tended to be 2 to 3 days later heading and maturing but produced more spikes per unit area. For the other traits measured, the differences between tall and short lines was in the range of 1 to 3 percent. The reduction in height (15 cm), however, resulted in a higher Fusarium Head Blight infection level and DON levels in the grain in inoculated nurseries. Variation was observed for grain yield and other traits among lines within the two height classes. Molecular markers for the Rht18 semi-dwarf gene were developed in order to differentiate between plants carrying the gene in either the heterozygous or homozygous states or those that were of a regular height. The KASP markers were validated on a panel of wheat varieties as well as series of wheat breeding lines in the CDC Bread Wheat breeding program. To conclude, the Rht18 gene was effective in reducing plant height and lodging; lines carrying the Rht18 gene tended to have a higher Harvest Index than tall lines, and the Rht18 gene did not affect grain yield. In addition, the increase in FHB levels associated with reduced stem elongation will require the selection of FHB resistant parentage in the deployment of this new dwarfing gene.