Interspecific Hybridisation of Boronias

Abstract

Interspecific hybridisation within the genus Boronia was attempted by using species with a range of chromosome numbers. Crosses were possible between Western Australian species including those with B. heterophylla as the female parent and pollen from B. molloyae (n = 8), B. megastigma (n = 7), B. purdienana (n = 9) and B. ramosa (n = 18). Cytological studies revealed that B. heterophylla genotypes had different chromosome numbers; ‘Red’ had 2n = 15, whereas ‘Moonglow’ and ‘Cameo’ had 2n = 14. The F ₁ hybrid from B. heterophylla ‘Red’ × B. megastigma had 2n = 15. Pollen viability, examined by using fluorescein diacetate, varied from 20% in B. crenulata to 80% in B. purdieana. Pollen of most species could be stored for 12 months in sealed containers at −20°C. Drying with silica gel desiccant did not improve storage, nor did ultra-low temperature (−196°C). Stored pollen was successfully used for interspecific hybridisation.