Molecular mapping of stripe rust resistance gene Yr51 in chromosome 4AL of wheat.

KEY MESSAGE: This manuscript describes the chromosomal location of a new source of stripe rust resistance in wheat. DNA markers closely linked with the resistance locus were identified and validated. A wheat landrace, AUS27858, from the Watkins collection showed high levels of resistance against Australian pathotypes of Puccinia striiformis f. sp. tritici. It was reported to carry two genes for stripe rust resistance, tentatively named YrAW1 and YrAW2. One hundred seeds of an F3 line (HSB#5515; YrAW1yrAW1) that showed monogenic segregation for stripe rust response were sown and harvested individually to generate monogenically segregating population (MSP) #5515. Stripe rust response variation in MSP#5515 conformed to segregation at a single locus. Bulked segregant analysis using high-throughput DArT markers placed YrAW1 in chromosome 4AL. MSP#5515 was advanced to F6 and phenotyped for detailed mapping. Novel wheat genomic resources including chromosome-specific sequence and genome zipper were employed to develop markers specific for the long arm of chromosome 4A. These markers were used for further saturation of the YrAW1 carrying region. YrAW1 was delimited by 3.7 cM between markers owm45F3R3 and sun104. Since there was no other stripe rust resistance gene located in chromosome 4AL, YrAW1 was formally named Yr51. Reference stock for Yr51 was lodged at the Australian Winter Cereal Collection, Tamworth, Australia and it was accessioned as AUS91456. Marker sun104 was genotyped on a set of Australian and Indian wheat cultivars and was shown to lack the resistance-linked sun104-225 bp allele. Marker sun104 is currently being used for marker-assisted backcrossing of Yr51 in Australian and Indian wheat backgrounds.