A recombined Sr26 and Sr61 disease resistance gene stack in wheat encodes unrelated NLR genes

The tall wheat grass-derived stem rust resistance genes Sr26 and Sr61 are among a few ones that are effective to all current dominant races of stem rust, including Ug99. Here, the authors show that the two genes are present in a small non-recombinogenic segment but encode two unrelated NLR proteins. The re-emergence of stem rust on wheat in Europe and Africa is reinforcing the ongoing need for durable resistance gene deployment. Here, we isolate from wheat, Sr26 and Sr61, with both genes independently introduced as alien chromosome introgressions from tall wheat grass (Thinopyrum ponticum). Mutational genomics and targeted exome capture identify Sr26 and Sr61 as separate single genes that encode unrelated (34.8%) nucleotide binding site leucine rich repeat proteins. Sr26 and Sr61 are each validated by transgenic complementation using endogenous and/or heterologous promoter sequences. Sr61 orthologs are absent from current Thinopyrum elongatum and wheat pan genome sequences, contrasting with Sr26 where homologues are present. Using gene-specific markers, we validate the presence of both genes on a single recombinant alien segment developed in wheat. The co-location of these genes on a small non-recombinogenic segment simplifies their deployment as a gene stack and potentially enhances their resistance durability.

Automated summary

Sr26 and Sr61 are effective stem rust resistance genes encoding two unrelated proteins, isolated from wheat with introgressions from tall wheat grass. They are present on a small non-recombinogenic segment, allowing for gene stacking and potentially enhancing resistance durability.