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Leaf defensive chemicals and Mycosphaerella leaf disease

Matthew Hamilton
University of Tasmania

In a collaborative project between CRC subprojects 4.2.8 (Alison Miller, Julianne O'Reilly-Wapstra, and Jon Humphreys) and 4.2.10, relationships between marsupial browsing leaf defence chemicals (macrocarpals, sideroxylonals, cineole and total phenolics ) and Mycosphaerella (now Teratosphaeria) Leaf Disease damage on juvenile foliage were explored.  Data were collected from two Eucalyptus globulus trials (Togari and Salmon River) established in 2005 in north-western Tasmania (see related article in this issue of Biobuzz). Significant genetic variation at the subrace and family within subrace levels was identified in the leaf defensive chemicals. Furthermore, a significant family (i.e. additive genetic) correlation between total phenolics and Mycosphaerella damage was found (-0.36, P=0.045), which suggests that increasing leaf phenolics may have an adverse effect on the fungus (leaf chemistry was assessed prior to infection by Mycosphaerella).  However, this negative relationship was not evident at the subrace level indicating that phenolics are not important drivers of subrace differences in Mycosphaerella susceptibility.

Biobuzz issue fourteen, May 2011