Linaria Mill. – a genus with ornamental value and breeding potential

The genus Linaria Mill. which consists of more than 150 species and belongs to the family Plantaginaceae is related to many commercially important ornamental plants such as Antirrhinum majus L., Angelonia Humb. et Bonpl., Digitalis L., Globularia L., Penstemon Schmidel, Veronica L., etc. Due to the genusRSQUO diversity and its ornamental potential a breeding program has started six years ago at the Humboldt University Berlin. Primary selections from seed sources (Linaria aeruginea (Gouan) Cav., Linaria genistifolia ssp. dalmatica (L.) Mill., Linaria maroccana Hook., Linaria purpurea (L.) Mill.) and seed accessions of Linaria vulgaris Mill. collected in urban areas and in wild habitats resulted in the genotypes later being used as breeding partners. Cross-breeding was performed in a partial diallel cross system. All 23 combinations produced seeds, but only seeds from 16 cross-combinations germinated. Several interspecific combinations showed symptoms of bastard bleaching in the F₁, which could be a consequence of incompatibility between parents’ genomes. A selected F₁ from Linaria vulgaris × Linaria purpurea, with intermediate flower coloration and growth pattern, was successfully backcrossed. F₁ and F₂ selections show potential for cut flower plants as well as garden and pot plants. The cross-breeding between Linaria vulgaris and Linaria genistifolia resulted in big, yellow-coloured flowers, with an orange mark on the lower lip. Due to heterosis effects, this combination seems to have the highest potential for ornamental purposes since flower size is an important breeding goal. According to the presented results, the genus Linaria can be added into the group of “new ornamentals” with high horticultural potential. Further breeding approaches such as polyploidization, additional interspecific hybridization, and strong selection will result in the first cultivars in the near future.