Fine Mapping of Using 90K SNP Chip Array and Flow-Sorted Chromosome Sequencing in Wheat.

Leaf rust, caused by , threatens global wheat production due to the constant evolution of virulent pathotypes that defeat commercially deployed all stage-resistance (ASR) genes in modern cultivars. Hence, the deployment of combinations of adult plant resistance (APR) and ASR genes in new wheat cultivars is desirable. Adult plant resistance gene was previously mapped on the long arm of chromosome 4B of cultivar VL404 and flanked by microsatellite markers (8.1 cM) and (10.1 cM), neither of which was sufficiently closely linked for efficient marker assisted selection. This study used high-density SNP genotyping and flow sorted chromosome sequencing to fine-map the locus as a starting point to develop a diagnostic marker for use in breeding and to clone this gene. Marker was mapped 0.4 cM proximal to , whereas a group of markers including were placed 0.6 cM distal to this gene. Testing of the linked markers on 75 Australian and 90 European cultivars with diverse genetic backgrounds showed that _ was most strongly associated with . Our results also show that the genomic region contains structural variation relative to the reference stock Chinese Spring, possibly an inverted genomic duplication, which introduces a new set of challenges for the cloning.