AbstractCommercial production of blackberries has traditionally been associated with areas where the climate is warmer than in Scotland; for example, parts of Europe and eastern North America, where the blackberries grown are of the Moriferi subsection of the genus Rubus, and western parts of North America where the blackberries grown are both the indigenous trailing blackberries of the Ursini subsection and blackberries of the Moriferi introduced from Europe. Blackberry-raspberry hybrids such as the 'Loganberry' and 'Boysenberry' were developed on the west coast of North America and have attained major importance there and also in New Zealand, where the climate is similar.
Blackberries have never attained major commercial importance in Europe. This is partly because the cultivars grown are unsuitable because they are either spiny, lack winter hardiness, ripen too late or have poor growth habits, and because wild forms are often freely available. Breeders have attempted to produce new cultivars with improvements in these characters from both the Moriferi and Ursini subsections. The two types have very different flavours: Ursini blackberries have a characteristic sharp flavour which is usually more aromatic than that of Moriferi blackberries. It is therefore ideal to have both, especially as the greater earliness of Ursini cultivars means that fruits of the two forms become available in succession.
In the Scottish program, first priority was given to breeding for spinelessness in both groups. Two genes for spinelessness are being used: the recessive gene (s) which originated from the diploid European species Rubus rusticanus var. inermis, and the dominant gene (SI) (Jennings, 1984), which originated in Texas, USA from an octoploid dewberry known as 'Austin Thornless'. Progress in breeding with each gene has been achieved by a combination of Anglo-American efforts over the past 50 years.