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Tailoring the onion crop for the 21st century. The development of high-quality fresh and processed onions

Contract nr: FAIR-CT95-0465
Project nr: 465
Project type: SC
Starting date: 01/03/1996
Duration: 60 months
Total cost: 3,206,000 EUR
EC Contribution: 1,603,000 EUR
Scientific Officer: Richard HARDWICK
Research topic: Plant health

The onion (Allium cepa L.) is the most widely cultivated horticultural crop in Europe. Annual production is gradually increasing and is now about 5x106 tons. The consumption of onion products is considered a growth market. Europe is not self sufficient in onions; we import sweet onion, and also dried onion products. To take advantage of potential, market opportunities for increasing the quality of the onion crop need to be identified and exploited. For onion, flavours and carbohydrates are the most important components of the internal quality. To meet the demands of the consumer, improved control of these constituents is needed both for the processing and the fresh market. However, our knowledge concerning these factors is limited and this limitation severely constrains our ability to influence quality components.

The objective of this proposal is the improvement of onion in fresh and dried form in order to meet the demands of the common EC market, to increase the competitiveness of European onions in global trade, and to comply with the EC policy of environment protection. The object is to increase our self-sufficiency and thereby to contribute to product quality and diversification.

The proposal has four interrelated objectives:
1) to evaluate the onion and its wild relatives' germplasm to reveal those parts of the gene pool that harbour maximum diversity for flavour and carbohydrate content;
2) to analyse flavour and carbohydrate pathways, from a molecular genetic, biochemical and physiological point of view;
3) to develop a new processing technology for onions;
4) to apply new molecular markers and develop a high density genetic linkage map for onions, to speed up breeding of better varieties.

Current situation/results:
To date, the EU onion quality project has been very successful both from a scientific and an applied point of view. Also an efficient European Allium research network has been formed over the past four years.
In the EU onion quality project, a broad spectrum of onion germplasm has been evaluated for traits related to the carbohydrate (CH) and flavour (FL) metabolism. Also, the nearest wild relatives of onion have been subjected to this screening. A core collection has been made early in the project and has been maintained to supply elite material to the participants.
On the basis of the evaluation for CH and FL traits, parents have been chosen for the development of breeding populations in which the genetic basis of the CH and FL traits are determined. Advanced breeding populations have been constructed during the project and currently, a genetic marker map is developed using advanced molecular markers (e.g. AFLP and microsattelites) on which genes governing the CH and FL traits will be located. This marker map will be important for the diversification of onion, as it allows efficient and quick development of new cultivars.
In-depth studies have been carried out to analyse the carbohydrate metabolism during bulbing and sprouting of onions. An in vitro model system was used to analyse the metabolic changes that took place during both processes. Key enzymes like SST, FFT and INV were monitored. Furthermore, the effects of differences in medium composition and light (spectrum, intensity) on the bulbing of onions were investigated. Moreover a long-term storage experiment was carried out in vitro, which was aimed at the maintenance of plant material in a gene bank. New fructan gene sequences have been cloned and are currently sequenced.
New methods have been developed in order to quantify the level of sulphur compounds in onions and their wild relatives. The two key enzymes in the flavour metabolism, alliinase and gamma glutamyl transpeptidase, have been studied. With respect to the alliinase enzyme, the sequences of the members of this gene family have been systematically analysed. With respect to the gamma glutamyl transpeptidase, the enzyme has been partially purified and N terminal sequencing together with heterologous PCR are currently being carried out in order to clone the gene.
New methods were investigated in order to process onions more efficiently. A combined microwave - hot air drying procedure proved to be most promising with respect to process criteria (maximum drying rate, drying duration, energy consumption, drying efficiency) and quality criteria (pyruvate content, non-enzymatic browning, rehydration kinetics).
All in all, this multidisciplinary research project has already provided promising tools to the whole EU onion production chain, which will make it more competitive on the world onion market.


Chris KIK
Plant Research International
PO Box 16
NL-6700 AA Wageningen
Tel.: +31 317 47 69 80
Fax: +31 317 41 80 94


  • Konrad BACHMANN
    Institute of Plant Genetics and Crop Plant Research (IPK)
    Corrensstrasse 3
    D-06466 Gatersleben
    Tel.: +49 394 825 466
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  • Brian THOMAS
    Horticulture Research International (HRI)
    UK-CV35 9EF Wellesbourne
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  • Remi KAHANE
    B.V. 1540
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  • Jean Claude LAGUERRE
    Institut Supérieur d'Agriculture Beauvais (ISAB)
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    B.P. 313
    F-60026 Beauvais
    Tel.: +33 1 30 75 62 35
    Fax: +33 1 30 75 62 21

  • Dimitris TZANOUDAKIS
    University of Patras
    Dept. of Plant Biology
    GR-26500 Patras
    Tel.: +30 61 99 72 79
    Fax: +30 61 99 72 79

  • Jacques AUGER
    Université de F. Rabelais
    IRBI, URA CNRS 1298
    Fac. des Sciences et Techniques
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    Fax: +33 2 47 36 70 52

  • Agnes RICROCH
    Université de Paris Sud
    CNRS Labo ESV
    Batiment 362
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    Fax: +33 1 69 15 73 53
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