Assessment of a non-destructive method to predict oil yield in Eucalyptus polybractea (blue mallee)

Eucalyptus oil is produced from a number of “oil mallee” species with high concentration of foliar essential oils, high proportion of 1,8-cineole and the ability to re-sprout with multiple stems from lignotubers after coppicing. Eucalyptus polybractea is one of the most planted mallees in Australia, but few efforts have been made to improve crop yields through selection or breeding programs, with the exception of seed collection from trees with high oil and 1,8-cineole concentration. The yield of essential oil from commercial eucalypt plantations is subject to several quantitative traits that interact, both positively and negatively. Using non-destructive methods we assessed traits relating to oil yield (quantitative and qualitative variation of foliar essential oils and biomass-related parameters) for their variability, heritability as well as phenotypic and genetic interactions in an open-pollinated progeny trial with 40 families and 480 individuals of E. polybractea. From this we built models to predict family yield performance and compared our predictions to commercial scale harvests of the same trial. Our models show that relying on oil concentration and 1,8-cineole proportion alone is not ideal for selection of top performing families. Rather a mixture of biomass related traits, foliar oil concentration, 1,8-cineole proportion and leaf architecture contribute to the top performing families in varying ways.