Both stable and unstable QTLs for resistance to powdery mildew are detected in apple after four years of field assessments

Powdery mildew, caused by the ascomycete fungus Podosphaera leucotricha, is one of the most damaging diseases of apple worldwide. Polygenically determined resistance might contribute to a significant increase of resistance to this disease in new cultivars. A quantitative trait locus (QTL) analysis w...

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Bibliographic Details
Published in:Molecular breeding 2006-05, Vol.17 (4), p.329-339
Main Authors: Calenge, F., Durel, C.-E.
Format: Article
Language:English
Subjects:
Airborne microorganisms
Apples
Ascomycetes
Biochemistry, Molecular Biology
Cultivars
Disease resistance
Fruits
Fungi
Gene mapping
Genes
Genetic crosses
Life Sciences
Malus
Molecular biology
Phenotypic variations
Plant biology
Podosphaera leucotricha
Powdery mildew
Progeny
Quantitative trait loci
Scab
Seasons
Stability
Stability analysis
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Summary:Powdery mildew, caused by the ascomycete fungus Podosphaera leucotricha, is one of the most damaging diseases of apple worldwide. Polygenically determined resistance might contribute to a significant increase of resistance to this disease in new cultivars. A quantitative trait locus (QTL) analysis was performed in an F1 progeny derived from a cross between the apple cultivar Discovery and the apple hybrid TN10-8. Powdery mildew incidence was assessed during four years (five seasons) in spring and/or autumn in a French local orchard. Seven additive and/or dominant QTLs were detected over the five seasons, with effects (R2) ranging from 7.5% to 27.4% of the progeny phenotypic variation. Two QTLs, on linkage groups (LGs) 2 and 13, were consistently identified and accounted together from 29% to 37% of the phenotypic variation according to the year of assessment. The other QTLs were identified during one (LGs 1, 14), two (LG10), or three (LGs 8, 17) seasons. Their instability indicated a changing genetic determinism according to the year of assessment, for which several hypotheses may be put forward. The QTLs on LGs 2 and 8 mapped close to clusters of resistance gene analogs (RGAs) and major genes for resistance to mildew or apple scab previously identified. The stable QTLs identified on LGs 2 and 13, together with the strong effect QTL located on LG 8, are of special interest for breeding purposes, especially if combined with other major resistance genes.
ISSN:1380-3743
1572-9788
DOI:10.1007/s11032-006-9004-7