Abstract
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.
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.