Theoretical and Applied Genetics (2004) 109, 1702-1709

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M. Gygax, L. Gianfranceschi, R. Liebhard, M. Kellerhals, C. Gessler and A. Patocchi (2004)
Molecular markers linked to the apple scab resistance gene Vbj derived from Malus baccata jackii
Theoretical and Applied Genetics 109 (8), 1702-1709
Abstract: Breeding for scab-resistant apple cultivars by pyramiding several resistance genes in the same genetic background is a promising way to control apple scab caused by the fungus Venturia inaequalis. To achieve this goal, DNA markers linked to the genes of interest are required in order to select seedlings with the desired resistance allele combinations. For several apple scab resistance genes, molecular markers are already available; but until now, none existed for the apple scab resistance gene Vbj originating from the crab apple Malus baccata jackii. Using bulk segregant analysis, three RAPD markers linked to Vbj were first identified. These markers were transformed into more reliable sequence-characterised amplified region (SCAR) markers that proved to be co-dominant. In addition, three SSR markers and one SCAR were identified by comparing homologous linkage groups of existing genetic maps. Discarding plants showing genotype-phenotype incongruence (GPI plants) plants, a linkage map was calculated. Vbj mapped between the markers CH05e03 (SSR) and T6-SCAR, at 0.6 cM from CH05e03 and at 3.9 cM from T6-SCAR. Without the removal of the GPI plants, Vbj was placed 15 cM away from the closest markers. Problems and pitfalls due to GPI plants and the consequences for mapping the resistance gene accurately are discussed. Finally, the usefulness of co-dominant markers for pedigree analysis is also demonstrated.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Andrea Patocchi, Cesare Gessler

Research topic(s) for pests/diseases/weeds:
resistance/tolerance/defence of host

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Venturia inaequalis Apple (Malus)