PAG-V: P186 - MAPPING OF A NEW EYESPOT RESISTANCE GENE, <i>Pch3</i>, IN WHEAT

Plant & Animal Genome V Conference

Town & Country Hotel, San Diego, CA, January 12-16, 1997.

P186

MAPPING OF A NEW EYESPOT RESISTANCE GENE, Pch3, IN WHEAT

YILDIRIM, AHMET(1), Stephen S. Jones(1), Timothy D. Murray(2)
1. Department of Crops and Soil Sciences, Washington State University, Pullman, WA 99164-6420
2. Department of Plant Pathology, Washington State University, Pullman, WA 99164-6430

Eyespot, caused by a facultative parasite Pseudocercosporella herpotrichoides (Fron.) Deighton (teleomorph Tapesia yallundae Wallwork & Spooner), is one of the most important diseases of winter wheat in the Pacific Northwest USA. Previously, there were only two resistance genes identified for eyespot, Pch1 and Pch2. Only Pch1 has been extensively utilized in many breeding programs because of the linked isozyme and RFLP markers. However, Pch1 does not provide complete resistance, and occurrence of new pathotypes of the pathogen that may circumvent this gene urged us to look for new resistance sources. Recently, we identified that Dasypyrum villosum, a distant relative of wheat, as being highly resistant to eyespot and mapped the resistance gene to chromosome 4V. An F₂ population was produced between a resistant 4V addition line and a susceptible disomic 4V substitution line. Ninety-eight F₂ plants were tested for disease reaction, and a 3:1 ratio was obtained, indicating that disease resistance was controlled by a single gene. The gene, named Pch3, was located on the long arm of chromosome 4V, and closely linked RFLP’s were identified. Mapping and tagging of Pch3 will enable breeders to combine all existing resistance genes into individual varieties with the goal of a more complete resistance.