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Reducing chemical input in apple production in response to consumer and producer environmental concerns by increasing the durability of natural disease resistance

Contract nr: FAIR-CT97-3898
Project nr: 3898
Project type: SC
Starting date: 01/01/1998
Duration: 52 months
Total cost: 2,480,500 EUR
EC Contribution: 1,406,800 EUR
Scientific Officer: Richard HARDWICK
Research topic: Plant health
Acronym: D.A.R.E.: Durable Apple Resistance in Europe

Durable disease resistance is one of the main objectives in apple breeding. Scab (caused by the fungus Venturia inaequalis) and powdery mildew (caused by the fungus Podosphaera leucotricha) are the two main apple diseases, affecting apple quality and yield when they are not strictly controlled by large amount of fungicides. In European orchards, chemical treatments cost 180 million ECU per year, with the overwhelming majority going towards scab and mildew control (15 to 20 specific treatments per year). Such a number of treatments raises numerous ecological problems and consumer health concerns, in addition to cost. Apple breeding strategies, based on monogenic resistance from wild related species, have been developed for 50 years, creating new resistant varieties. Recently, many newly-created resistant varieties have been attacked by new races of scab, showing the vulnerability of such monogenic resistance when confronted by pathogen dynamics. New ways of breeding need to be developed, to strenghten resistance already obtained and to achieve durable resistance in apple crops. Polygenic resistance should give much more durable resistance, especially if combined with monogenic resistance by using new molecular biology tools. At the same time, the risk of appearance of new fungal virulences has to be assessed.

Within this framework, this project aims to develop plant material, a pathogen observation network, basic knowledge and methodologies for the creation and marketing of new apple varieties carrying durable resistance against these two detrimental fungi. It involves several major objectives:

1) characterisation of new apple cultivars carrying durable disease resistance;
2) assessment of the risks of appearance of new virulences;
3) genetic dissection of polygenic resistance taking into account pathogen variability;
4) development of new breeding strategies;
5) marketing analysis of several new resistant hybrids.

Expected results:
The project will increase our knowledge about the expression and mechanisms of plant resistance to the two fungi, the genetic bases of monogenic and polygenic resistance, the pathogen variability in Europe and consumer preferences regarding newly-selected resistant hybrids. The expected benefits are as follows:

  • establishment of collections of V. inaequalis and P. leucotricha strains present in Europe;
  • identification of traditional cultivars and newly-selected hybrids carrying a broad spectrum of resistance to scab and mildew;
  • production of numerous new progenies combining contrasted and 'large spectrum' resistances, selection of 'elite' genotypes combining different type of resistances,;
  • identification of numerous molecular markers useful for further marker-assisted selection.

The complementary expertise of geneticists, pathologists, breeders and nurserymen are key factors in the efficient utilisation of the results of this project. In addition to the economic and ecological impact of the acquisition of durable (stable) disease resistance in apple, the project will make the apple a useful model for many other fruit tree species, with potential repercussions on their breeding strategies for durable resistance.

Current situation:
A large range of cultivars, hybrids and wild species of apple have been characterised in the glasshouse and in the orchard for their resistance to scab and mildew with various strains/inocula of the 2 fungi. Several of these cultivars show resistance symptoms to a large spectrum of inocula and are potential sources for further breeding programmes. A European network of core-orchards has been established to assess the risk of appearance of new virulences of V. inaequalis in different environmental conditions. Two European core-collections of V. inaequalis and P. leucotricha strains have also been constructed. Strains are now characterised for their pattern of pathogenicity on several apple cultivars and will be used soon for new pathological tests, either on the previous large range of cultivars or on progenies developed for genetic mapping.

Numerous molecular and biochemical markers (AFLP, SSR, isozymes, etc.) have been identified in several progenies derived from crosses between susceptible and resistant cultivars. One genetic map is already saturated. A second one is quite finished, and three further ones are in progress. The progenies are being evaluated for scab and mildew resistance. Chromosome regions involved in partial resistance to these two diseases will be mapped soon. Specific markers have also been found closed to three major mildew resistance genes.

Resistance gene pyramiding has been initiated. In particular, marker-assisted selection gave reliable results for scab resistance selection.
Sensory evaluation of scab resistant cultivars in supermarkets and laboratory conditions gave many results on consumer preferences and will help the promotion of future new resistant varieties.


INRA - Institut National de la Recherche Agronomique
Address of the Institute:
Rue de l'Université 147
F-75338 Paris
Address of the coordinator:
Unité d'Amélioration des Espèces Fruitières et Ornementales
Rue Georges Morel 42
BP 57
F-49071 Beaucouzé cedex
Tel.: +33 2 41 22 57 51
Fax: +33 2 41 22 57 55


    PRI - Plant Research International
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  • Cesare GESSLER
    ETHZ - Swiss Federal Institute of Technology
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  • FAW - Eidgenössische Forschungsanstalt für Obst -, Wein- und Gartenbau
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    HRI - Horticulture Research International
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  • Silviero SANSAVINI
    DCA-BO - Universita' di Bologna
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  • Athanasios MANGANARIS
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  • Marc LATEUR
    CRA - Centre de Recherches Agronomiques
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  • Elina GRILLET
    Les Naturianes® Sarl
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