The effect of cold stratification on germination in 28 cultural relict plant species : with the purpose of establishing germination protocols

Sammanfattning: Cultural relict plant species from the Nordic countries have been collected by the Nordic Genetic Resource Center (NordGen) for the purpose of conservation. To ensure high seed vitality in store, regular germination tests need to be conducted. It is important to get a correct viability status, but the knowledge of seed dormancy in the cultural relict plants is often poor. The objective of this study was to investigate how seed dormancy is affected by cold stratification. The study includes 31 accessions from 28 species with the purpose of establishing germination protocols. Furthermore, the study includes three treatments: 0, 2 and 4 weeks cold stratification, followed by germination tests. The dormancy of 22 of the species was not affected by stratification and 10 of them showed unsatisfying germination percentage (<75 %), probably due to poor seed health or high proportion of immature seeds. Five species benefited of stratification, though the low temperature may be questioned as a dormancy-breaking factor in Thymus pulegioides that germinated during the stratification period. Cold stratification reduced seed germination rate in one of the examined species, something which may be due to secondary dormancy or fungal infection. In addition, the effect of cold stratification in combination with scarification was studied in 4 accessions of non-relict plants: three accessions of Trifolium pratense and one accession of Allium ursinum. It showed an inter-accessional variation in germination response for T. pratense but no response for A. ursinum.