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  • 1
    ISSN: 1432-2242
    Keywords: Key words Apple ; Scab resistance ; Introgression ; Vf gene ; DNA markers ; Linkage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A chromosomal region originating from Malus floribunda 821 confers Vf scab resistance to many isolates of Venturia inaequalis. Twelve DNA markers located in this region were used to scan the equivalent of 31 cM in 98 Malus accessions. This allowed a molecular diagnosis of a source of resistance in apple germplasm with the aid of pedigree information, and in the context of a limited marker survey representing other chromosomes. At least five marker alleles were present in all scab-resistant breeding selections or varieties arising from M. floribunda. The validity of findings based on RAPD markers was confirmed with SCAR assays and Southern-hybridisation experiments. The order of markers determined in previous mapping studies was confirmed and sets of recombinants identified that establish reliable fine-mapping orders within 0.7 cM of the resistance locus. None of the marker alleles were present in the accessions that are either susceptible or possess weak polygenic resistance to scab. The presence of some alleles corresponding to those present at least 5.3 cM from Vf in M. floribunda was detected in some accessions. Other major sources of scab resistance do not appear to possess alleles in common with the Vf region, which will simplify future allelism tests. The results are discussed in the context of the introgression of resistance loci together with marker-assisted selection. The use of breeding pedigrees to assist in fine-scale mapping and map-based cloning is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5060
    Keywords: Malus ; apple ; genetic mapping ; isozymes ; DNA techniques ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A recently initiated collaborative project involving apple breeders in seven European countries is described. The objective is to improve the European apple crop by molecular-aided breeding to increase efficency and reduce the time-scale in breeding for resistance, tree habit and fruit quality. The strategy adopted provides a model for similar studies in fruit, forest and other woody species. The project is based on progenies from a small number of crosses involving many important agronomic genes. Replication of these reference progenies by vegetative propagation will enable studies to be carried out simultaneously in each country. By developing a range of molecular markers, including isozymes, RFLPs and sequence-tagged DNA probes, an integrated molecular map is being constructed for use in a wide range of breeding and genetic studies. Construction of a database recording many mapped molecular markers will enable efficient exploitation of data in future genetic, breeding and physiological studies of apple. Aspects of the adopted strategy, techniques and management are discussed in the context of mapping genes in perennial crop genomes.
    Type of Medium: Electronic Resource
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