DNA markers linked to Malus floribunda 821 scab resistance

Abstract

Breeding resistant apple plants is an alternative way to control fungal pathogens reducing the environmental impact due to the use of pesticides. The breeding of apple cultivars resistant to Venturia inaequalis could be much improved by marker-assisted selection. A molecular marker closely linked to the resistance locus called Vf could replace selection based on infection studies. To find such molecular markers, DNA of progenies from crossings of a resistant and a susceptible apple tree was subject to bulked segregant analysis. Two markers were found with a genetic distance of 10.6% and 19.7% recombination frequency to the Vf locus.

Molecular markers linked to the apple scab resistance gene Vbj derived from Malus baccata jackii

“…The success rate of 0.6% can be considered quite low; however, this result does not differ greatly from previous studies which identified RAPD markers linked to the dominant resistant gene Vf (Koller et al 1994;Yang and Krüger 1994;Tartarini 1996;Gardiner et al 1996). This can be explained by the use of heterozygous resistant bulks, which reduce the probability of detecting polymorphism by 50% (Melchinger 1990).…”

“…The progeny seedlings were inoculated with a suspension of V. inaequalis field conidia (4×10 5 conidia/ml) as described by Gianfranceschi et al (1996). Assessment of susceptibility and resistance was performed macroscopically after 10-12 days and rated in six classes (Chevalier et al 1991) DNA extraction, bulked segregant analysis and RAPD amplification DNA was extracted as described by Dellaporta's protocol (Dellaporta et al 1983), with minor modifications following Koller et al (1994).…”

“…A total of 506 random ten-base Operon-primers (Operon Technologies) were evaluated via PCR under the following conditions: amplification reaction volume was 15 μl containing 10 mM Tris-HCl (pH 9.0); 50 mM KCl; 1.5 mM MgCl 2 ; 100 μM each of dATP, dCTP, dGTP, dTTP (Roche, Switzerland); 0.3 μM primer; 5 ng genomic DNA; and 0.85 U Taq DNA Polymerase (Pharmacia). Amplification was performed in a PerkinElmer GeneAmp PCR System 9600 following Koller et al (1994). Amplicons were separated on 1% agarose gels with 0.5× TBE and stained with ethidium bromide.…”

“…They have been singularly incorporated into commercial apples or selections, which makes them available for breeding purposes (MacHardy 1996). For all of them except Vbj, molecular markers have been developed: Vf (between others: Koller et al 1994Vinatzer et al 2004; Vr (Hemmat et al 2002); Vb and Va (Hemmat et al 2003); and Vm (Cheng et al 1998). Two other apple scab resistance genes, Vx and Vr2, and molecular markers associated to them have recently been identified (Hemmat et al 2002;Patocchi et al 2004).…”

Vr 2 : a new apple scab resistance gene

“…The popularity of Vf has encouraged many researchers to study this resistance. This has led to the discovery of several molecular markers linked to Vf (Koller et al 1994;Gianfranceschi et al 1996;Tartarini 1996;Tartarini et al 1999). These markers were later used to begin the positional cloning of the gene (Vinatzer et al 1998;Patocchi et al 1999a, b;Vinatzer et al 2001) resulting in the cloning of the first apple scab resistance gene (Barbieri et al 2003, Belfanti et al 2004.…”