Mapping a gene conferring resistance toPseudocercosporella herpotrichoideson chromosome 4V ofDasypyrum villosumin a wheat background

The objectives of this study were to map and tag the previously undescribed eyespot resistance gene PchDv on chromosome 4V of Dasypyrum villosum in a wheat background. The 82 F2plants used for mapping were produced from a cross between a susceptible wheat 'Yangmai-5' (4V(4D)) substitution line and a resistant wheat 'Chinese Spring' disomic addition line of chromosome 4V of D. villosum. Segregation for resistance and susceptibility among F2plants was 3:1, indicating that resistance was controlled by a single dominant gene. PchDv mapped to the distal part of chromosome 4V and was bracketed by two RFLP markers, Xcdo949 and Xbcd588, in a 33-cM interval. This distance could not be reduced, owing to a lack of polymorphic loci in this region. Theoretically, double recombination in this region occurs in 3.3% of the individuals; therefore, 96.7% of the selected genotypes would have PchDv, with simultaneous selection for both flanking markers. Double recombination between the flanking markers was observed in 2 out of 82 (2.4%) F2individuals.