Variable resistance to Quambalaria pitereka in spotted gum reveal opportunities for disease screening

Abstract

Quambalaria shoot blight, caused by the fungus Quambalaria pitereka, is a serious disease affecting the development of spotted gum (Corymbia citriodora subsp. citriodora, C. citriodora subsp. variegata, C. henryi and C. maculata) plantations in subtropical and tropical Australia. Incorporation of screening for resistance to Q. pitereka into current breeding programs is essential for the future development of plantations using spotted gum and Corymbia hybrids. The aim of this study was to determine whether there is variability in resistance among and within different species provenances and families of spotted gum to infection by Q. pitereka. A secondary aim was to consider whether the origin of seed source is a significant indicator of resistance to Q. pitereka. Assessments were conducted in trials consisting of spotted gum provenances, families and clones, all at the same site with high levels of disease pressure and with optimum climatic conditions for disease development. While all species and provenances of spotted gum could be infected by Q. pitereka, results showed that there are high levels of variability in resistance between and within species, provenances and families, indicating the potential to select for disease resistance. Provenance was shown to be an unreliable indicator of resistance to Q. pitereka.