Abstract:
Quambalaria shoot blight (QSB) has emerged recently as a severe disease of Corymbia calophylla (marri). In this study, QSB
damage and growth were assessed in Corymbia calophylla trees at 4 and 6 years of age in two common gardens consisting
of 165 and 170 open-pollinated families representing 18 provenances across the species’ natural distribution. There were
significant differences between provenances for all traits. The narrow-sense heritability for growth traits and QSB damage at
both sites were low to moderate. The genetic correlation between QSB damage and growth traits was negative; fast-growing
families were less damaged by QSB disease. Age-age genetic correlations for individual traits at four and six years were very
strong, and the type-B (site–site) correlations were strongly positive for all traits. Provenances from cooler wetter regions
showed higher resistance to QSB. The QSB incidence at 6 years was significantly correlated with environmental factors of
the provenance’s origin. The QSB incidence at years four and six was not correlated with the QSB expression in 3-month-old
seedlings. Based on these results, selection for resistance could be undertaken using 4-year-old trees. There is potential for
a resistance breeding program to develop populations of marri genetically diverse and resistant to QSB.
