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Resistance to Scald (Rhynchosporium secalis) in Barley (Hordeum vulgare) Studied by Near-Isogenic Lines: I. Markers and Differential Isolates

First, second, fourth, and fifth authors: Department of Horticulture and Crop Sciences, P.O. Box 5022, Agricultural University of Norway, N-1432 Ås, Norway; third author: Cereal Research Center, Agriculture Canada, Winnipeg, Canada; sixth author: Pajbjergfonden, DK-8600 Odder, Denmark; seventh author: Norwegian Crop Research Institute, N-1432 Ås, Norway; and eighth author: Department of Plant Breeding Research, Swedish University of Agricultural Sciences, S-75007 Uppsala, Sweden

Near-isogenic lines (NILs) with resistance for scald in seventh generation backcross with ‘Ingrid’ as recurrent parent (RP) were tested with seven differential isolates of Rhynchosporium secalis in Norway and Canada. NILs of ‘Turk’, ‘Brier’, ‘CI 8162’, ‘La Mesita’, ‘Hispont’, ‘Atlas 46’, ‘Modoc’, ‘Hudson’, ‘Abyssinian’, ‘Steudelli’, and ‘CI 2222’ also were evaluated for field reactions. The genetic characterization of the NILs (degree of isogeneity with Ingrid) and with each other was carried out. The molecular marker pattern shows that the backcrossing program has resulted in from 86.3 to 100% RP genome in the NILs, depending on the marker system. On an average, 96% RP genome was found in the NILs. There were certain consistent (pairwise) differences between the NILs and RP on chromosomes 3H and 7H. Both chromosomes are known to contain loci conferring resistance to R. secalis, indicating successful introgression from the donors into the NILs. Approximately two-thirds of the observed RP-NIL polymorphisms were linked to the assumed resistance in the NIL. Based on the marker and phenotypic analyses of the NILs, suggestions for a more appropriate and updated terminology of genes for resistance to R. secalis in barley are made. The proposed changes in nomenclature also indicate the differentials that are available as NILs and those lacking.

Additional keywords: differential varieties, molecular markers, NILs, PCA, resistance genes.