Marker Development and Saturation Mapping of the Tan Spot Ptr ToxB Sensitivity Locus Tsc2 in Hexaploid Wheat

Abstract

Ptr ToxB is a host-selective toxin produced by the tan spot fungus, that induces chlorosis in wheat lines harboring the gene, which was previously mapped to chromosome arm 2BS in tetraploid wheat ( L.). In this study, molecular mapping in a recombinant inbred line (RIL) population derived from the Ptr ToxB-sensitive ‘Katepwa’ and the Ptr ToxB-insensitive landrace Salamouni (Salamouni × Katepwa [SK] population) confirmed the location of on 2BS in hexaploid wheat ( L.). Analysis of an F population derived from the same parents indicated that a single dominant gene governed Ptr ToxB sensitivity. Thirteen microsatellite markers were used to construct a basic linkage map of the region in the SK population, and 14 additional markers developed from bin-mapped expressed sequence tags (ESTs) and from ESTs identified based on colinearity with rice ( L.) and (L.) P. Beauv. were mapped to the region. was delineated to a 3.3 cM interval and cosegregated with marker . Spore inoculations and composite interval-regression mapping demonstrated that a compatible -Ptr ToxB interaction accounted for 54% of the variation in disease expression. Analysis of Ptr ToxB-sensitive and-insensitive genotypes suggested that is diagnostic for and should be useful for marker-assisted selection.