Mapping Resistance Genes for Oculimacula Acuformis in Aegilops Longissima.

Eyespot is an economically important winter wheat disease in the U.S. Pacific Northwest. Oculimacula acuformis is one of two species of the soilborne fungi that causes eyespot of wheat, the other being O. yallundae. Both pathogens often coexist in the same field and produce elliptical lesions on stem bases of wheat that are indistinguishable. Pch1 and Pch2 are the only two eyespot resistance genes readily available to wheat breeders, but neither provides complete control. A new source of eyespot resistance was identified from Aegilops longissima (2n = 14, S^lS^l), a wild relative of wheat. QTL for resistance to O. yallundae were detected in chromosomes 1S^l, 3S^l, 5S^l, and 7S^l in a recombinant inbred line (RIL) population developed from the cross Aegilops longissima accessions PI 542196 (R) x PI 330486 (S). Three QTL for resistance to O. acuformis were mapped in chromosomes 1S^l, 3S^l, and 5S^l using the same population that explained 66% phenotypic variation by GUS score and 84% by visual rating. These QTL had LOD values of 10.6, 8.8, and 6.0 for GUS score, respectively, and 16.0, 10.0, and 13.0 for visual rating, respectively. However, no QTL for resistance to O. acuformis were found in chromosome 7S^l. QTL associated with resistance to O. acuformis have similar chromosomal locations as those for resistance to O. yallundae, and thus, it appears that some genes or genes at the same loci in Ae. longissima may control resistance to both eyespot pathogens. QTL effective against both pathogens will be most useful for breeding programs and have potential to improve the effectiveness and genetic diversity of eyespot resistance.