Identification of an RFLP interval containing Pch2 on chromosome 7AL in wheat.

The gene Pch2 in 'Cappelle Desprez' is one of two genes found in hexaploid wheat known to confer resistance to eyespot disease. This study was conducted to develop an RFLP linkage map of the distal portion of wheat chromosome 7AL, and to locate and identify markers closely associated with Pch2 for use in marker-assisted selection. Ten loci in addition to Pch2 were mapped on chromosome 7AL, using segregation data from 102 homozygous chromosome 7A recombinant substitution lines derived from 'Chinese Spring' x 'Chinese Spring' ('Cappelle Desprez' 7A). The Pch2 locus was bracketed by two RFLP markers, one 11.0 cM distal to Xcdo347 and the other 18.8 cM proximal to Xwg380. The position of Pch2 on chromosome 7AL is similar to that of Pch1 on chromosome 7DL, suggesting that these resistance genes are homoeoloci. Although no single marker was closely linked to Pch2, simultaneous selection of the flanking RFLP markers Xcdo347 and Xwg380 could be used for selecting Pch2, since double recombination occurred in only 3% of the recombinant population. The use of the flanking RFLP markers to select for Pch2, in combination with previously identified Pch1-linked markers, would facilitate the development of cultivars carrying two genes for resistance to eyespot.