| Eyespot of wheat, caused by two fungal pathogens Oculimacula yallundae and O. acuformis, produces elliptical lesions at the stem base that result in lodging of infected plants and yield losses up to 50% in commercial wheat fields. The objectives of this research were: 1) to identify potential new sources of resistance to O. yallundae and O. acuformis from a wild relative of wheat, Ae. longissima (2n = 14, S1S 1); and 2) to understand the genetic control of the resistance and map gene(s) in the S1 genome by developing a genetic linkage map based on wheat microsatellite markers.;Forty Ae. longissima accessions and 83 Ae. longissima genetic stocks in a Chinese Spring or Selkirk background were evaluated for resistance to eyespot. Forty-five percent of the accessions were resistant to O. yallundae, 53% were resistant to O. acuformis , and 35% were resistant to both pathogens. This is the first evidence that Ae. longissima contains resistance genes to eyespot. Ae. longissima chromosomes 1S1, 2S1, 5S1, and 7S1 contributed to eyespot resistance and indicated that eyespot resistance was controlled by multiple regions of the S1 genome. Differential resistance reactions to O. yallundae and O. acuformis were observed in 28% of Ae. longissima accessions and 40% genetic stocks.;A recombinant inbred line (RIL) population was developed from the cross of Ae. longissima accessions PI 542196 (R) x PI 330486 (S) to map eyespot resistance genes. A genetic linkage map of the S1 genome was constructed with 169 wheat microsatellite markers covering 1261.3 cM in 7 groups. F5 lines (189) were tested for reaction to O. yallundae and four QTL were detected in chromosomes 1S1, 3Sl, 5S1, and 7S1. These QTL explained 44% of the total phenotypic variation by GUS scores and 63% by visual ratings. This is the first time multiple QTL conferring resistance to eyespot in the S 1 genome have been identified. Markers Xcfd6, Xwmc597, Xwmc415 , and Xcfd2 are tightly linked to Q.Pch.wsu-1S 1, Q.Pch.wsu-3S1, Q.Pch.wsu-5S1, and Q.Pch.wsu-7S1, respectively. The identification of these markers will facilitate QTL transfer to wheat by marker-assisted selection and broaden the genetic diversity of eyespot resistance.;... |
