Identification by genome scanning approach (GSA) of a microsatellite tightly associated with the apple scab resistance geneVm

Abstract

For all known major apple scab resistance genes except Vr, molecular markers have been published. However, the precise position of some of these genes, in the apple genome, remains to be identified. Knowledge about the relative position of apple scab resistance genes is necessary to preliminarily evaluate the probability of success of their pyramidization. Pyramidization of different resistance genes into the same genotype is a reliable way to create cultivars with durable apple scab resistance. Applying the genome scanning approach (GSA), we identified the linkage group of the scab resistance gene Vm, derived from Malus micromalus, and we found a new molecular marker tightly associated with the gene. The simple sequence repeat Hi07h02, previously mapped on linkage group 17, cosegregates with the Vm gene (no recombinants in the 95 plants tested). The already published sequence-characterized amplified region Vm marker OPB12(687) was found to be linked at about 5 cM from the resistance gene and, therefore, this marker also maps on linkage group 17 of apple. This is the first report of the discovery of a major apple scab resistance gene on linkage group 17. The advantages of using GSA for the identification of molecular markers for qualitative traits are discussed.

Microsatellite markers spanning the apple (Malus x domestica Borkh.) genome

“…In only one case, Z71981 SSR (LG15), is the approximate map position still to be determined. Some SSRs of the Hi set have already been mapped in other crosses than Fiesta × Discovery, and their map position relative to other SSRs was confirmed (Patocchi et al 2005;Gardiner et al 2006;Erdin et al 2006;Durel, unpublished).…”

“…Recognition of SSR associations led to the identification of clusters of resistance genes (e.g., Bus et al 2004) and to the first integrated map of apple that reviews many papers with regard to the location of scab resistance genes . The recent discovery of many new gene-SSR marker associations, made necessary a new update of this integrated map with recently mapped scab resistance genes (Bus et al 2005a,b;Patocchi et al 2005), thus continuously improving our understanding of the organization of the apple genome.…”

“…Firstly, the Genome Scanning Approach (GSA, Patocchi and Gessler 2003) allows efficient mapping of major genes. This procedure was successfully applied to map the apple scab resistance genes Vr2, Vm Patocchi et al 2005), and Vb (Erdin et al 2006). Secondly, the Pedigree Genotyping concept was developed , which allows the exploitation of breeding material in the assessment of marker-trait associations and in allele mining by using multiple pedigreed plant populations, which can be any combination of crosses, cultivars, and breeding lines.…”

Identification and stability of QTLs for fruit quality traits in apple

“…Much of the initial excitement over the potential benefits of QTLs however has been tempered by the realisation that the results of individual QTL mapping experiments need to be validated over different years, growth sites, generations and genetic backgrounds, and currently, the results of such studies are still a long way from being implemented as a part of standard breeding practices. By comparison, MAS and MAB for monogenic traits such as apple scab (Venturia inaequalis) resistance are already in use (Xu et al 2001;Gygax et al 2004;Vinatzer et al 2004;Patocchi et al 2005). …”

Pyramidisieren von Schorfresistenzen in der Apfelzüchtung

“…Die meisten bekannten Resistenzgene sind bereits in Zuchtlinien integriert worden, womit schon viele unerwünschte Eigenschaften der Wildsorten eliminiert wurden. Dieses Züchtungsmaterial erhöht im weiteren Kreuzungsprozess die Wahrscheinlichkeit, auch kommerziell interessante Kreuzungsnachkommen zu erhalten (Patocchi et al , 2005.…”