Sr65 : a widely effective gene for stem rust resistance in wheat

Key message Sr65 in chromosome 1A of Indian wheat landrace Hango-2 is a potentially useful all-stage resistance gene that currently protects wheat from stem rust in Australia, India, Africa and Europe. Abstract Stem rust, caused by Puccinia graminis f. sp. tritici ( Pgt ), threatened global wheat production with the appearance of widely virulent races that included TTKSK and TTRTF. Indian landrace Hango-2 showed resistance to Pgt races in India and Australia. Screening of a Hango-2/Avocet ‘S’ (AvS) recombinant inbred line population identified two stem rust resistance genes, a novel gene (temporarily named as SrH2 ) from Hango-2 and Sr26 from AvS. A mapping population segregating for SrH2 alone was developed from two recombinant lines . SrH2 was mapped on the short arm of chromosome 1A, where it was flanked by KASP markers KASP _ 7944 (proximal) and KASP_12147 (distal). SrH2 was delimited to an interval of 1.8–2.3 Mb on chromosome arm 1AS. The failure to detect candidate genes through MutRenSeq and comparative genomic analysis with the pan-genome dataset indicated the necessity to generate a Hango-2 specific assembly for detecting the gene sequence linked with SrH2 resistance. MutRenSeq however enabled identification of SrH2 -linked KASP marker sunCS_265 . Markers KASP_12147 and sunCS_265 showed 92% and 85% polymorphism among an Australian cereal cultivar diversity panel and can be used for marker-assisted selection of SrH2 in breeding programs. The effectiveness of SrH2 against Pgt races from Europe, Africa, India, and Australia makes it a valuable resource for breeding stem rust-resistant wheat cultivars. Since no wheat-derived gene was previously located in chromosome arm 1AS, SrH2 represents a new locus and named as SR65 .