Development of the First Imidazolinone-Resistant Triticale Through Introgression of Mutant AHAS Alleles from Wheat

Across diverse agroecological environments worldwide, triticale provides economically competitive grain yields, high nutritional quality comparable to wheat, tolerance to drought and poor soil conditions, and resistance to several diseases commonly affecting rye. Despite its growing importance, triticale production relies largely on agronomic practices similar to those used in wheat. However, its greater sensitivity to several herbicides commonly used in wheat complicates weed management, making the development of herbicide-resistant triticale cultivars an important opportunity to facilitate broader adoption of this crop. The objective of this study was to develop triticale lines resistant to imidazolinone herbicides through introgression of resistance from a mutant Triticum aestivum line generated by 60Co gamma irradiation. Mutant wheat plants were treated with the recommended field rate of imazamox–imazapyr at the tillering stage, and a surviving plant was used as the source of imidazolinone resistance. This mutant was crossed with a triticale breeding line used as the female parent. The progeny was advanced to the F5 generation and treated with imazamox–imazapyr to confirm resistance. This breeding and selection process resulted in the stabilized triticale lines 5202 and 5195. Partial sequencing of the AHAS gene revealed a Ser-653-Asn substitution associated with imazamox–imazapyr resistance in both lines. Allele-specific sequencing further revealed contrasting AHAS sequence signatures between the resistant lines, suggesting differences in the genomic distribution of the resistance allele. Both resistant triticale lines survived the recommended field rate of imazamox–imazapyr applied either pre- or post-emergence, although they differed significantly in their response to the herbicide, with line 5195 consistently exhibiting the highest level of resistance. These findings highlight the value of induced mutagenesis as a source of novel agronomic variation for cereal breeding. Beyond facilitating direct weed control, these first imidazolinone-resistant triticale lines may provide an important agronomic advantage in crop rotations where residual imidazolinone activity limits the establishment of winter cereals.