Adult plant stem rust resistance in durum wheat Glossy Huguenot: mapping, marker development and validation

Adult plant stem rust resistance locus, QSrGH.cs-2AL, was identified in durum wheat Glossy Huguenot and mendelised as Sr63. Markers closely linked with Sr63 were developed. An F₃ population from a Glossy Huguenot (GH)/Bansi cross used in a previous Australian study was advanced to F₆ for molecular mapping of adult plant stem rust resistance. Maturity differences among F₆ lines confounded assessments of stem rust response. GH was crossed with a stem rust susceptible F₆ recombinant inbred line (RIL), GHB14 (M14), with similar maturity and an F_6:7 population was developed through single seed descent method. F₇ and F₈ RILs were tested along with the parents at different locations. The F₆ individual plants and both parents were genotyped using the 90 K single nucleotide polymorphism (SNP) wheat array. Stem rust resistance QTL on the long arms of chromosomes 1B (QSrGH.cs-1BL) and 2A (QSrGH.cs-2AL) were detected. QSrGH.cs-1BL and QSrGH.cs-2AL were both contributed by GH and explained 22% and 18% adult plant stem rust response variation, respectively, among GH/M14 RIL population. RILs carrying combinations of these QTL reduced more than 14% stem rust severity compared to those that possessed QSrGH.cs-1BL and QSrGH.cs-2AL individually. QSrGH.cs1BL was demonstrated to be the same as Sr58/Lr46/Yr29/Pm39 through marker genotyping. Lines lacking QSrGH.cs-1BL were used to Mendelise QSrGH.cs-2AL. Based on genomic locations of previously catalogued stem rust resistance genes and the QSrGH.cs-2AL map, it appeared to represent a new APR locus and was permanently named Sr63. SNP markers associated with Sr63 were converted to kompetetive allele-specific PCR (KASP) assays and were validated on a set of durum cultivars.