Molecular mapping of the wheat powdery mildew resistance gene Pm24 and marker validation for molecular breeding

Molecular markers were identified in common wheat for the Pm24 locus confer ring resistance to different isolates of the powdery mildew pathogen, Erysi phe graminis DM f. sp, tritici (Em. Marchal). Bulked segregant analysis was used to identify amplified fragment length polymorphism (AFLP) markers and microsatellite markers linked to the gene Pm24 in an F-2 progeny from the cross Chinese Spring (susceptible)X Chiyacao (resistant). Two AFLP markers XACA/CTA-407 and XACA/CCG-420, and three microsatellite markers Xgwm106, Xg wm337 and Xgwm458, were mapped in coupling phase to the Pm24 locus. The AFL P marker locus XACA/CTA-407 co-segregated with the Pm24 gene, and XACA/CCG- 420 mapped 4.5 cM From this gene. Another AFLP marker locus XAAT/CCA-346 co segregated in repulsion phase with the Pm24 locus. Pm24 was mapped close to the centromere on the short arm of chromosome 1D, contrary to the previous ly reported location on chromosome 6D, Pm24 segregated independently of gen e Pm22, also located on chromosome 1D. An allele of microsatellite locus Xg wm337 located 2.4+/-1.2 cM from Pm24 was shown to be diagnostic and therefo re potentially useful for pyramiding two or more genes for powdery mildew r esistance in a single genotype.