Discovery of the New Leaf Rust Resistance Gene Lr82 in Wheat: Molecular Mapping and Marker Development

Abstract

Breeding for leaf rust resistance has been successful worldwide and is underpinned by the discovery and characterisation of genetically diverse sources of resistance. An English scientist, Arthur Watkins, collected pre-Green Revolution wheat genotypes from 33 locations worldwide in the early part of the 20th Century and this collection is now referred to as the ‘Watkins Collection’. A common wheat genotype, Aus27352 from Yugoslavia, showed resistance to currently predominating Australian pathotypes of the wheat leaf rust pathogen. We crossed Aus27352 with a leaf rust susceptible wheat selection Avocet S and a recombinant inbred line (RIL) F6 population of 200 lines was generated. Initial screening at F3 generation showed monogenic segregation for seedling response to leaf rust in Aus27352. These results were confirmed by screening the Aus27352/Avocet S RIL population. The underlying locus was temporarily named LrAW2. Bulked segregant analysis using the 90K Infinium SNP array located LrAW2 in the long arm of chromosome 2B. Tests with molecular markers linked to two leaf rust resistance genes, Lr50 and Lr58, previously located in chromosome 2B, indicated the uniqueness of LrAW2 and it was formally designated Lr82. Kompetitive allele-specific polymerase chain reaction assays were developed for Lr82-linked SNPs. KASP_22131 mapped 0.8 cM proximal to Lr82 and KASP_11333 was placed 1.2 cM distal to this locus. KASP_22131 showed 91% polymorphism among a set of 89 Australian wheat cultivars. We recommend the use of KASP_22131 for marker assisted pyramiding of Lr82 in breeding programs following polymorphism check on parents.

Genetic mapping of the wheat leaf rust resistance gene Lr19 and development of translocation lines to break its linkage with yellow pigment

“…To date, 82 wheat leaf rust resistance (Lr) genes have been formally catalogued (Dinh et al 2020; Kumar et al 2021; Bariana et al 2022;Xu et al 2022), nearly half of which were derived from wild wheat relatives (Prasad et al 2020). Of the 82 known Lr genes, only nine have been cloned (Feuillet et Lin et al 2022).…”

Phenotypic response of a core collection of Aegilops triuncialis accessions to wheat leaf rust and expression pattern of genes involved in resistance

“…A resistance that confers protection against pathogen isolates throughout the life cycle of the plant is classified as all‐stage resistance (ASR), while resistance at the post‐seedling stage is referred to as adult‐plant resistance (APR). Accordingly, pyramiding APR and ASR genes might confer long‐lasting resistance in the host plant against rust pathogens (Bariana et al., 2022).…”