2. Materials and methods
2.1. Plant materials
The NCGR Rubus seed-collection database was screened and
8 species belonging to six subgenera were selected from the
germplasm collections stored for 1–23 years at −20 ◦C (Table 1).
Accessions were selected with seed of variable sizes that had
30–95% TZ viability and a large amount of seed, so that seeds of the
accession were still available for distribution. Rubus leucodermis,
Rubus niveus, Rubus odoratus, and Rubus parviflorus were used for
four germination treatments (750 seed each) and four species with
fewer available seed (Rubus arcticus, R. chamaemorus, Rubus sanctus,
and Rubus urticifolius) were used for two germination treatments
(450 seed each).