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New breeding strategies in lettuce for better adaptability to conditions of organic farming and improved resistance against Bremia lactucae

Project


Project code: 2810OE069
Contract period: 05.05.2011 - 28.02.2015
Budget: 256,232 Euro
Purpose of research: Applied research

The increasing demand of organically produced lettuce can be met only by enlarging the assortment and stabilizing the yield. Cultivating lettuce of a high quality safely requires varieties with improved stress tolerance, a well-developed ability to utilize nutrients, a low demand of water, as well as a high resistance to pathogens, particularly to downy mildew. To achieve this aim, two breeding methods were tested and evaluated in a project supported in the framework of the German Federal Programme of Organic Farming and Other Forms of Sustainable Agriculture. One of them was planting mixtures of pure, phenotypically similar lines comparing them with their offspring, which was harvested in bulk. The other one comprised testing the work with crossed populations. For that aim phenotypically similar lines were crossed, which was continued to the F4 generation, always harvesting in bulk, which should result in a slightly heterozygous plant to be brought to cultivation in the field. The results of four-year studies in the field in three locations showed that line mixtures and crossed populations reacted in a far more stable way to stressors than pure varieties. High losses caused by B. lactucae occurred less often, and infection was less severe. Total losses like in pure varieties were not noticed. The homogeneity of mixtures in the habitus is high enough at least for direct marketing and retail. The homogeneity in harvest maturity comparable with the one in pure lines may be achieved by the composition of the line mixtures. A first field cropping test in organic farms has been assessed very positively.

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