Sundhet hos utsäde: gränsvärden, metoder och beredskap

Healthy seeds are essential for achieving high-quality yields. At the same time, seeds constitute an effective pathway for the spread of plant pathogens, both between growing seasons and across geographical areas. Seed certification, including seed health testing, therefore plays a vital role in integrated plant protection. In principle, all seeds placed on the market must be certified and meet established seed health requirements. Seed-borne diseases affect germination, crop establishment, yield, and quality. The location of the infection within the seed and its biological behaviour determine how it is analysed, which threshold values are applied, and whether treatment is possible. In Sweden, quantitative threshold values are mainly applied to seed-borne fungal diseases in seed-propagated crops. For bacteria, viruses, and nematodes, EU plant health legislation generally requires seeds to be free from infection. Threshold values are used as a basis for decisions on certification, treatment requirements or recommendations not to use the seed. These thresholds vary between crops, diseases and certification classes, and their function ranges from absolute prohibitions to advisory guidelines. Most of the threshold values currently used in Sweden were developed in the 1970s and 1980s. Since then, cultivation systems, climate, pathogen occurrence and available treatment options have changed, meaning that many threshold values are no longer fully adapted to current conditions. Seed health testing is currently based primarily on traditional culture-based methods, such as agar, filter paper, embryo, osmosis and washing methods. These methods are well established, cost-effective and reliable for routine analyses, but they are often time-consuming, dependent on mycological expertise and may have limited sensitivity at low infection levels. New methods, particularly molecular techniques, offer higher sensitivity and faster analysis, but cannot always distinguish between viable and non-viable pathogen material. Consequently, they are currently considered mainly suitable as a complement to existing methods. Threshold values should be updated using a clear and systematic methodology. Such values must balance biological risk and economic consequences, while taking available treatment options into account. This methodology should include the selection of appropriate analytical methods, a biologically relevant definition of infection level, controlled multi-year field trials, and identification of the infection level at which effects on crop establishment, disease development and yield become evident. Summary From a preparedness perspective, Sweden's seed supply appears partly vulnerable. The country relies on imports for certain crops, as well as for key inputs and analytical services. A long-term, sustainable system for seed health is essential for effective plant protection, crop quality and Sweden's food supply, both under normal conditions and in times of crisis. The report identifies three key needs: updated and scientifically grounded threshold values that reflect current growing conditions; effective use of both existing and alternative analytical methods; and the importance of a national capacity for seed diagnostics and production in the event of a crisis.