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Biobuzz 6 - genetic control of eucalypt defensive chemistry (4.2.8)

The aim of this research is to breed plantation eucalypts that are unpalatable to cute furry animals ...

Plant secondary metabolites play an important role in herbivore defence. In the case of eucalypts, there is increasing evidence that chemicals such as the formylated phloroglucinols (FPCs) and essential oils (e.g. cineole) that reside in the leaves influence herbivory by mammals and arthropods (Keszei et al. 2008). The possibility of manipulating the levels of defensive chemicals through classical selection and enhancing the resistance of deployment populations of Eucalyptus globulus and E. nitens is being investigated as part of an ARC Linkage grant held by the University of Tasmania (UTas) and Forestry Tasmania (FT) which is complementary to subproject 4.2.8.

Understanding the genetic control of defensive chemicals in these species is fundamental to this research. A quantitative genetic approach is being taken in this UTas/FT ARC Linkage grant.  However, of interest is the genomic work being undertaken at UTas (ARC Discovery grant) and the Australian National University, aimed at locating regions of the eucalypt genome (QTL) and ultimately the genes responsible for the variation in these defensive chemicals. This work will no doubt eventually lead to DNA markers for key defensive chemicals being included in the future ‘genetic toolbox’ available for screening eucalypt germplasm.

Recent publications by these research groups have detected genomic regions affecting defensive chemicals in E. globulus (Freeman et al. 2008) and E. nitens (Hennery et al. 2007).  Genomic regions affecting two major FPCs, sideroxylonal A and macrocarpal G, which have been implicated in the defense of E. globulus against browsing by brushtail possums and pademelons, have been detected.

Of particular interest has been the fact that one of the genomic regions affecting sideroxylonal A concentrations in juvenile leaves of E. globulus appears to be the same as that affecting concentrations in adult leaves of E. nitens.  This ‘co-location’ gives confidence in these results and suggests that the same gene may be active in both the adult and juvenile leaves.  If this is the case then selection on seedlings will affect adult leaf chemical concentrations and vice versa

Prof Brad Potts
School of Plant Science
University of Tasmania