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Chemical defence responses of Australian Acacia trees to infection by Ceratocystis albifundus and C. manginecans

Benedicta Swalarsk-Parry: Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria

<div>Australian <em>Acacia mearnsii </em>and <em>A. manginum </em>are considered highly productive timber plantation trees in the southern hemisphere. However, these trees are highly susceptible to infections by <em>Ceratocystis albifundus</em> and <em>C. manginecans</em> respectively, which both cause high losses in wood and pulp production. The aim of this study was to determine how <em>Acacia</em> trees defend themselves against infections by these pathogens and the basis for their susceptibility. Artificial inoculation of young saplings from both tree species was conducted. Analysis of the defence hormones produced in response to fungal colonization revealed that both tree species produce adequate levels of the plant defence hormone jasmonic acid-isoleucine, which is an early signal for initiating defence mechanisms against infection by necrotrophic pathogens. However, tannin levels in both tree species were down-regulated after infection. On the other hand, an increase in flavonoid concentrations in infected saplings was observed. Further research will elucidate if the trade-off between flavonoids and tannins influences susceptibility of Australian <em>Acacia </em>trees during infection by <em>Ceratocystis</em> species.</div>