Inbreeding and Interspecific Hybridization in Eucalyptus gunnii

Results of a hybridization programme in France showed that the success and vigour of progeny of self-fertilization and close intraspecific crosses of Eucalyptus gunnii were significantly lower than for wide intraspecific crosses and a range of interspecific crosses. E. gunnii females demonstrated wide crossability, with the success of most interspecific hybrid combinations tried with species from the section Maidenaria being n.s.d. from that of wide intraspecific crosses. The only major barrier to interspecific hybridization found was with E. globulus. There was no strong association between crossability and the taxonomic/genetic distance between parents, although after 1 year of plantation growth F₁ hybrids from the only interseries cross examined (E. gunnii x E. ovata) showed reduced vigour. The implications of these results for the development of breeding strategies as well as for gene flow and hybridization in natural populations are discussed.