Discovery of a novel non-race-specific adult-plant resistance (APR) locus conferring stripe rust immunity in spelt wheat and its suppression in bread wheat.

A novel non-race-specific adult-plant resistance locus, QYr.cbl-5D, from spelt wheat confers near-immune resistance to stripe rust. The resistance conferred by QYr.cbl-5D is suppressed in bread wheat from an unknown suppressor. Adult-plant resistance (APR) genes provide durable, non-race-specific resistance against wheat rust diseases. We identified a novel APR locus in the spelt wheat cultivar CDC Silex that confers non-race-specific near-immune resistance to stripe rust. The trait segregates as a single dominant gene in the CDC Origin/CDC Silex spelt populations, and bulked segregant analysis sequencing (BSA-seq) mapped the locus, QYr.cbl-5D, to a 0.31 Mb interval on chromosome 5D, confirming monogenic inheritance. Interestingly, introgression into bread wheat suppresses this resistance, a pattern consistent with a dominant suppressor or another background-dependent modifier. We generated a scaffold-scale assembly of CDC Silex to annotate the locus and its flanking region on 5D. Within a ± 1 Mb interval flanking the QYr.cbl-5D peak, six genes were identified, of which five had no predicted function and one encodes a DnaJ/HSP-C2H2 zinc-finger fusion protein. Future work will aim to clone this APR and identify the molecular basis of its suppression in bread wheat. Linked SNPs from this region will enable marker-assisted selection to deploy this APR locus, providing a durable resistance resource to support sustainable wheat breeding and reduce reliance on fungicides.