Resistance to O culimacula yallundae and O culimacula acuformis is conferred by P ch2 in wheat

The recent report of a differential response of wheat lines containing the P ch2 gene to infection with the eyespot pathogens O culimacula yallundae and O . acuformis has prompted this re‐examination of the response to these fungi by the recombinant lines used to map P ch2 . Homozygous recombinant substitution lines ( RSL ) derived from the hybridization of C hinese S pring ( CS ) and the CS chromosome substitution line C appelle D esprez 7A ( CS / CD 7A), previously evaluated for response to glucuronidase ( GUS )‐transformed O . yallundae , were evaluated for response to infection with GUS ‐transformed O . acuformis . Based on visual scores and on GUS expression level, which reflects fungal colonization of seedling plants, evidence of a quantitative trait locus ( QTL ) conferring resistance to O . acuformis was found in two separate growth chamber experiments (logarithm of the odds, LOD , = 2·7 and 6·7 at 305 and 289 cM, respectively) that was equivalent in location to that for resistance to O . yallundae ( LOD = 13·2 and 11·4 at 289 and 304 cM, respectively). These results confirm that P ch2 confers some degree of resistance against both O . yallundae and O . acuformis under these conditions.