Corymbia species and hybrids: a solution to Queensland hardwood plantations?

Hardwood plantations are relatively new in northern Australia. Of the species available, the spotted gums are the most important commercial hardwood plantation taxon for high quality timber in the humid and sub-humid zones of Queensland and northern New South Wales. The domestication and genetic improvement of the spotted gums (Corymbia citriodora subsp. citriodora (CCC), C. citriodora subsp. variegata (CCV) and C. henryi (CH) however only commenced in Queensland in 1997. Since then seed orchards and progeny trials have been established for all three species. One major failing of these species is all provenances are somewhat susceptible (Dickinson et al 2004) to the fungal disease, Ramularia Shoot Blight caused by Quambalaria pitereka (Simpson 2000). In amenity plantings and wind breaks of C. torelliana, hybrids with the spotted gum species were noticed that had great vigour, good form and resistance to Ramularia Shoot Blight. As a consequence a breeding program has been initiated in Queensland, to hybridise the spotted gum species with C. torelliana (CT). This paper reports on the genetic base of each species and presents preliminary result on the performance of these species and hybrids in trials