Conifer resistance to bark beetles

Biochemistry of Conifer Resistance to Bark Beetles and Their Fungal Symbionts... 

The role of monoterpene enantiomers In Imparting differential conifer resistance to bark beetle attack has received little attention because of the difficulties In... 

Johnson, M, A. and R. Croteau, Biochemistry of conifer resistance to bark beetles and their fungal symbionts, in Ecology and Metabolism of Plant Lipids (G. Fuller and W. D. Nes, eds.), ACS Symposium Series 325,76-92, American Chemical Society, Washington, DC, 1987. 

Conifers exhibit resistance to bark beetle attack and fungal invasion because of an Induced synthesis and flow of secondary resin which contains high levels of volatile monoterpenes. Monoterpene olefin synthases (geranyl pyrophosphate cyclases) were found in higher levels in fungus-infected lodgepole pine seedlings than in uninfected controls. 

The effect of enantiomeric monoterpenes on bark beetle activity is very significant. In some cases, as little as 2-5% of an enantiomeric product will completely inhibit the effect of the active form and greatly upset the normal pheromonal system of the insect. Fungi are also sensitive to these effects. For example, (-f )-a-pinene (14) is three times more inhibitory than (— )-a-pinene against the blue stain fungus, Cerat-ocystis spp. The differential expression of the cyclases responsible for coproduction of enantiomeric monoterpenes may determine the highly selective resistance response conifers exhibit toward bark beetles and their fungal symbionts (Johnson and Croteau, 1987). 

Berryman AA (1972) Resistance of conifers to invasion by bark beetle-fungus associations. 

The biochemical bases for the terpenoid-mediated interactions of conifers with bark beetles and their fungal symbionts is understood in broad outline. Resistance to colonization ultimately resides In the species-specific arsenal of terpenoids which can be snistered in response to an attack. Resistant... 

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