Rust resistance in barley accessions County and BHS248

Abstract Rusts can cause devastating losses of barley ( Hordeum vulgare L.) in epidemic years. Several reactions to Puccinia hordei ( Rph ) genes/quantitative trait loci (QTLs) for resistance to barley leaf rust (BLR) have been documented. In contrast, there is a dearth of characterized resistance sources against stem rust (SR) caused by Puccinia graminis . This study aimed to genetically characterize novel and known SR and BLR loci in the resistant barley accessions County and BHS248. To achieve this, two recombinant inbred line (RIL) populations ( n = 200) were developed using Hiproly as a rust‐susceptible parent. QTL mapping was performed utilizing genotypic data predominantly generated on the barley 50k iSelect single‐nucleotide polymorphism array and phenotypic results from multi‐year trials in South Africa and USA. A major QTL on chromosome 4H ( QPgt.cg‐4_CH ) for adult plant resistance (APR) to SR race PTKST explained up to 18.2% variation. Another major QTL on 5H (designated QPgt.cg‐5_CH ), also effective to PTKST, is likely RPG‐qtl‐5H‐11_11355 . The APR gene Rph20 (herein named QPh.cg‐5.1_CH ) and all‐stage resistance gene Rph27 (designated QPh.cg‐4_BH ) mapped to 5H and 4H, respectively. For BLR, major effect APR QTLs were identified on 2H and 6H in both populations. Published markers were used to assess if the 6H resistance was contributed by Rph24 , but the latter locus did not map to 6H. Kompetitive allele specific PCR assays were designed spanning most of the major QTL identified. These should be useful in tracking the introgression of rust resistance in local germplasm.