Towards an improved variety assortment for the Dutch organic sector : case studies on onion and spring wheat

A.M. Osman

Research output: Thesisinternal PhD, WU


Key words:

organic farming; principles of organic agriculture; food production chain;

plant breeding; genetic correlation; plant traits; farmers’ preferences;

variety testing; Value for Cultivation and Use; EU seed legislation;

onion; Allium cepa; spring wheat; Triticum aestivum; baking quality


Variety choice is an important component of organic crop management. The organic sector pursues to produce healthy, nutritious food without using synthetic inputs and excessive amounts of natural resources. Access to varieties that are able to cope with weeds, diseases and pests, and thrive well under an organic fertility management regime, allows actors in the organic food production chain to achieve these aspirations. In this thesis I analyse how the current breeding, variety assessment and registration process should be changed to provide varieties that fulfil the needs of organic farmers, traders and processors. The research is based on the cases of two crops, onion (Allium cepa) and spring wheat (Triticum aestivum), that differ in key issues that influence the options for change: breeding and variety registration aspects; organic seed and crop production issues; destination of the harvest; and composition of and relations between actors in the production chain.

Variety trials, in which we evaluated onion and spring wheat varieties for traits prioritized by organic stakeholders, revealed that the variety assortment displayed important weaknesses when grown and processed organically. In the case of onion, farmers needed varieties with improvements for resistances against main diseases, root system, storability and erect plant types in combination with high yield. For spring wheat, weed suppressiveness and baking quality were the key traits that required improvements.

Interviews with conventional onion breeders showed that they focussed on yield and post-harvest traits (storability, bulb quality). In addition to these traits, breeding for the organic sector would require breeders to pay more attention to the selection of field traits like partial resistance against leaf diseases and a better root system. To improve key traits for organic growers, selection should take place in a growing environment without the fungicides and herbicides that are typically applied in conventional nurseries.

Interviewing conventional wheat breeders made clear that selection for the organic market would conflict with achieving the high yield demanded by conventional growers. Breeders have achieved high yields by increasing the harvest index, which goes at the expense of baking quality through a relative decrease in protein content. Based on a literature review, we propose two alternative approaches to improve yield and protein content simultaneously: selection for increased total biomass or/and selection for protein quality. The first approach would deliver taller, leafier varieties that are also more competitive against weeds. Improving protein quality would require selection under low nitrogen input or organic growing conditions as protein composition is strongly influenced by soil nitrogen availability. Analysis of data of our own conventional and organic variety trials, together with datasets from other European countries showed that for other important traits (e.g., yield, disease resistance, plant length) selection for the organic sector could also be conducted in non-organically managed breeding nurseries, which typically refrain from fungicides and growth regulator applications, as genetic correlations for these traits were high (0.8 -1.0).

Conducting variety trials in organic fields and evaluating these for traits prioritized by the stakeholders make results more relevant for the latter. In the specific case of Value for Cultivation and Use (VCU) testing, that is part of the official variety registration procedure of field crops in the EU, adapting the research protocol proved crucial to provide market access to varieties better adapted to organic production. The organic spring wheat VCU testing resulted in the inclusion of varieties in an organic section of the Dutch Recommended List of Varieties, showing that the statutory variety testing system is flexible to address new needs. However, procedures are costly and not in proportion to market size and in this way prohibit the release of varieties for organic and other small markets.

Although specifically wheat breeders proved to be open to consider adaptations in their programme, the relatively small market prevents conventional private sector breeders from investing in selecting varieties specifically targeted at the organic sector. Therefore we elaborate options to set up a way of breeding that is in line with organic principles and overcomes this economic barrier.



Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
  • Lammerts van Bueren, Edith, Promotor
  • Struik, Paul, Promotor
  • Almekinders, Conny, Co-promotor
Award date2 Sep 2014
Place of PublicationWageningen
Print ISBNs9789462570689
Publication statusPublished - 2014


  • allium cepa
  • onions
  • triticum aestivum
  • spring wheat
  • organic farming
  • varieties
  • cultivars
  • variety trials
  • varietal reactions
  • variety classification
  • plant breeding

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