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Journal of Applied Genetics 49(4), 2008, pp. 321-331

Resistance to Melampsora larici-epitea leaf rust in Salix: analyses of quantitative trait loci

Ann-Christin Ronnberg-Wastljung, Berit Samils, Vasilios Tsarouhas, Urban Gullberg

Abstract: Quantitative resistance of Salix to Melampsora larici-epitea leaf rust was studied in 2 Salix mapping populations. One population was a backcross between a S. schwerinii × S. viminalis hybrid and S. viminalis, and the other was an F2 population between S. viminalis and S. dasyclados. A leaf disc bioassay was used to study the components of quantitative resistance (latent period, uredinia number, and uredinia size) to 3 isolates of the leaf rust. The analysis of quantitative trait loci (QTLs) revealed 9 genomic regions in the backcross population and 7 genomic regions in the F2 population that were important for rust resistance, with QTLs explaining 8-26% of the phenotypic variation. An important genomic region was identified for the backcross population in linkage group 2, where QTLs were identified for all resistance components for 2 of the rust isolates. Four of the QTLs had overlapping mapping intervals, demonstrating a common genetic background for latent period, uredinia diameter, and uredinia number. QTLs specific to some rust isolates and to some resistance components were also found, indicating a combination of common and specific mechanisms involved in the various resistance components. Breeding implications in relation to these findings are discussed.

Key words: leaf disc inoculation, Melampsora larici-epitea, Salix dasyclados, Salix viminalis, Salix schwerinii, QTL mapping, quantitative resistance

Correspondence: A-C. Ronnberg-Wastljung, Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Box 7080, SE-750 07 Uppsala, Sweden; e-mail:

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