Genomic location of stripe rust resistance in a hexaploid derivative of durum wheat Glossy Huguenot and development of closely linked markers

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating fungal disease that affects wheat production in many regions of the world. The identification and characterisation of new sources of host plant resistance is required to enrich the existing gene pool. Durum wheat landrace Glossy Huguenot showed high level of resistance to stripe rust in the field. To utilise this resistance in wider wheat germplasm, we transferred it to common wheat cultivar Westonia. A backcross₂F₅ (BC₂F₅) line (WGH54) which showed high levels of all stage resistance against the then prevalent Pst pathotypes was crossed with the susceptible parent Avocet S (AvS) and F_2:3 generation was raised. Monogenic segregation was observed among WGH54/AvS F_2:3 families. Bulked segregant analysis using iSelect wheat 90 K Infinium SNP array mapped the stripe rust resistance on chromosome 2A. The gene was temporarily named as YRWGH54. Single nucleotide polymorphism (SNP) markers were used to refine the location of YRWGH54. Genotyping showed chromosomal rearrangements in this genomic region when compared with the Chinese Spring (CS) reference sequence. Stripe rust resistance gene YR32 was located on chromosome 2AL previously and markers linked with it were mapped in the same region as YRWGH54. Greenhouse tests with recent Pst pathotypes showed same virulence/avirulence specificity suggesting that YRWGH54 and YR32 may be the same. Closely linked KASP markers identified in this study will be useful for marker assisted pyramiding of YRWGH54 with other marker-tagged stripe rust resistance genes in future wheat cultivars to achieve durable control.