Red clover (Trifolium pratense L.) is the most important forage legume in the Nordic region, but its utilization is limited by poor persistency. The improvement of cultivated red clover can potentially take advantage of the numerous wild populations and landraces conserved in gene banks; however, there is often limited information available on the phenotypic and genetic characteristics of this material. We characterized 48 populations conserved at NordGen for a number of traits and compared them to commercial cultivars. The material was evaluated in field trials at four locations over two years and in an experiment under controlled conditions. Considerable variation was identified, with stem length, growth type and flowering date having the highest broad sense heritabilities. Traits related to plant size were strongly associated with late flowering and upright growth and differed between landraces/cultivars on the one hand and wild populations on the other. There was a large genotype by environment interaction on winter survival, which only partially correlated with freezing tolerance under controlled conditions. A majority of gene bank accessions exceeded the commercial cultivars in winter survival and freezing tolerance and can therefore be a genetic resource for future improvement of these traits. The phenotypic variation among accessions was associated with two main axes of climatic variation at the collection site. Petiole length of young plants under controlled conditions as well as plant size in the field increased with increasing summer temperature and decreasing summer precipitation, while number of leaves and an apparent vernalization requirement, recorded under controlled conditions, increased with decreasing annual and winter temperature. We discuss the implications these results have for collection, conservation and utilization of red clover genetic resources in the Nordic region.

中文翻译：

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遗传资源的性状表征揭示了改进的栽培北欧红三叶草的有用变异

红三叶草（红三叶L.）是北欧地区最重要的饲草豆类，但其利用受到持久性差的限制。栽培红三叶草的改良可潜在利用基因库中保存的众多野生种群和地方品种；但是，有关这种材料的表型和遗传特性的信息通常很少。我们对在NordGen保护的48个种群的许多特征进行了表征，并将其与商业品种进行了比较。两年来，在四个地点的现场试验中以及受控条件下的实验中对材料进行了评估。鉴定出相当大的变异，其中茎长，生长类型和开花日期具有最高的广义遗传力。与植物大小有关的性状与后期开花和直立生长密切相关，一方面在地方品种/品种与另一方面在野生种群之间存在差异。环境相互作用对冬季生存有很大的基因型，与控制条件下的耐寒性仅部分相关。大多数基因库登录品在冬季存活率和抗冻性方面超过了商业品种，因此可以作为将来改良这些性状的遗传资源。种质之间的表型变化与收集地点的两个主要气候变化轴相关。随着夏季温度的升高和夏季降水的减少，在受控条件下的幼小植物的叶柄长度以及田间的植物大小都增加了，而在受控条件下记录的叶片数量和明显的春化处理要求随着年度和冬季温度的降低而增加。我们讨论了这些结果对北欧地区红三叶草遗传资源的收集，保存和利用的影响。