Multiple field and glasshouse assessments increase the reliability of linkage mapping of the Vf source of scab resistance in apple |
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Authors: | G J King F H Alston L M Brown E Chevreau K M Evans F Dunemann J Janse F Laurens J R Lynn C Maliepaard A G Manganaris P Roche H Schmidt S Tartarini J Verhaegh R Vrielink |
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Institution: | (1) Horticulture Research International, Wellesbourne, Warwick CV35 9EF, UK Fax: +44(0)1789 470552 E-mail: graham.king@hri.ac.uk, GB;(2) Horticulture Research International, East Malling, West Malling, Kent ME19 6BJ, UK, GB;(3) DLO-Centre for Plant Breeding and Reproduction Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands, NL;(4) Federal Centre for Breeding Research on Cultivated Plants, Institute for Ornamental Plant Breeding, Bornkampsweg 31, D-22926, Ahrensburg, Germany, DE;(5) INRA Station d’Amelioration des especes fruitieres et ornamentales, Centre de Recherches d’Angers, 49070 Beaucouze, France, FR;(6) Pomology Institute Naoussa, P.O. Box 122, 59200 Naoussa, Makedonia, Greece, GR;(7) Dipartimento di Colture Arboree, University of Bologna, Via Filippo Re 6, 40126, Bologna, Italy, IT |
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Abstract: | Apple scab, caused by the fungus Venturia inaequalis (Cke.) Wint., is an important disease in commercial apple production. A mapping population of 155 individuals, derived from
a cross between the apple varieties ‘Prima’ (resistant)בFiesta’ (susceptible), was scored for response to the disease in
replicated field and glasshouse trials throughout Europe. Twenty data sets were selected and cluster analysis was used to
form a consensus score for the population fitting a 1 : 1 segregation ratio of resistance:susceptibility. The progeny were
scored with molecular markers. A detailed map covering 54 cM of the ‘Prima’ linkage group containing the Vf gene for scab resistance was constructed using 24 molecular markers linked to the resistance gene. One isoenzyme marker (Pgm-1), six RFLP markers and 17 RAPD markers formed a linkage group with the consensus measure of resistance to scab. Four marker
bridges were established with the corresponding ‘Fiesta’ linkage group with additional markers (one isozyme, one RFLP, three
RAPD and one AFLP). A low chi-square value indicated a good fit of the marker ordering, which was in close agreement with
previously reported linkage positions for some of the markers and Vf. Differences were observed in the ability of different scoring methods to resolve susceptible and resistant classes. The
results obtained for the consensus classification of resistance to scab for the population may suggest the presence of virulent
inocula at some sites, which could overcome the Vf gene for resistance. The consequences of relying on individual scoring occasions for studying Vf scab resistance are discussed in the context of linkage analysis, conventional breeding selection, and marker-assisted selection.
Received: 23 July 1997 / Accepted: 31 October 1997 |
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Keywords: | Malus Apple Venturia Scab resistance Linkage mapping Cluster analysis |
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