Evaluation of advanced potato clones in <strong>organic</strong> <strong>and</strong> conventional conditions Ilze Skrabule State Priekuli <strong>Plant</strong> Breeding Institute, Cesis, Latvia The development of <strong>organic</strong> farming raises requirement to suitable varieties <strong>for</strong> <strong>organic</strong> growing conditions. The evaluation of potato varieties in <strong>organic</strong> fields brought out most important traits <strong>for</strong> <strong>organic</strong> potato production, which should contain <strong>organic</strong> potato variety. As the most important trait resistance to different pathogens, (late blight, black scurf, virus diseases, rhizoctonia etc.) has been notified (Zimnoch-Guzovska, 2003; Tiemens-Hulscher et all., 2003; Vogt-Kaute, 2001). The desired traits <strong>for</strong> <strong>organic</strong> potato <strong>breeding</strong> are adaptability to <strong>organic</strong> fertilizations (adequate root system, rapid juvenal root <strong>and</strong> plant development, good growth vigour, efficient mineral uptake <strong>and</strong> use), ability to give yield in short growing period (early bulking <strong>and</strong> ripening, yield stability, reaching acceptable quality, good storability) (Tiemens- Hulscher et all., 2003) <strong>and</strong> compliance to marketing. A part of named traits are included in conventional potato <strong>breeding</strong> programmes, but some of characters are particularly significant <strong>for</strong> <strong>organic</strong> growing conditions. As conventional <strong>and</strong> <strong>organic</strong> growing conditions are different, requirements to varieties are different too; should these differences be a reason <strong>for</strong> creating separate <strong>breeding</strong> activities (Colon et all., 2003). One of ways is to start <strong>breeding</strong> <strong>for</strong> <strong>organic</strong> farming in conventional programme <strong>and</strong> at defined generation evaluates probably acceptable clones in <strong>organic</strong> conditions. The aim of study is to compare evaluation of selected clones from conventional <strong>breeding</strong> programme in conventional <strong>and</strong> <strong>organic</strong> growing conditions. In 2006 <strong>and</strong> 2007 nine potato clones (4th field generation) have been evaluated in conventional <strong>and</strong> <strong>organic</strong> fields. The clones were selected according assessment of leaf coverage, maturity, resistance to late blight of foliage, starch content in under conventional growing conditions. The earliness, resistance to pests in field, the length of growing period, yield, starch content <strong>and</strong> others were evaluated <strong>and</strong> compared in both growing conditions. The suitability of clones to <strong>organic</strong> growing conditions will be assessed. The plant emergence was little faster in <strong>organic</strong> field due to presprouting, but later the development was similar to each clone in both fields. If compared to st<strong>and</strong>ard variety ‘Brasla’, one clone tuber yield was significantly higher in <strong>organic</strong> field, but in conventional field four varieties exceeded ‘Brasla’. The starch content <strong>for</strong> almost all clones was higher in <strong>organic</strong> field than in conventional field. The <strong>breeding</strong> of new varieties <strong>for</strong> <strong>organic</strong> farming could be done in conventional conditions as part of existing <strong>breeding</strong> programme in the early generations (hybridisation, first year selection). Results of this trial proof, that selection <strong>for</strong> <strong>organic</strong> conditions have to be done in <strong>organic</strong> field, as selected preferably suitable genotypes in conventional field did not fit to <strong>organic</strong> conditions as expected. 21
Selection Criteria 22
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