Terpenes, as well as terpenoids, are the major components of the defense resin. Major terpenoids found in pine oleoresin were monoterpenes, sesquiterpenes, and diterpenoid resin acids. The terpene composition were previously correlated with resistance to bark beetle attack. Southern pine beetle (SPB), Dendroctonus frontalis, is native to southern United States and carries mites and several fungi. Recent variations in the climate resulted in an expansion of southern pine beetle to the north-eastern United States. In Connecticut, SPB has been found in several economically important conifer species including pitch, Scots, red, and white pines as well as Norway spruce. In the early stages of attack, SPB vectors blue-stain fungi Ophiostoma minus perhaps to overwhelm the plant response. In this study, naïve eastern white pine trees were inoculated with O minus. Phloem tissue samples were collected from eastern white pine trees after 28 or 65 days and flash frozen. Tissues were further pulverized in liquid nitrogen and extracted using 50 µM p-cymene (internal standard) containing hexane. A standard curve was prepared using serial dilution of standard mixtures. Extracted samples were analyzed using gas chromatography-mass spectrometry (GC-MS) fitted with a ZB-Wax (30 m × 0.32 µm × 0.25 µM) column. Monoterpenes such as α-pinene, β-pinene, β-myrcene, terpinolene and limonene were found to be induced significantly due to fungal attack indicating the presence of an induced defense mechanism within the trees.

Induced monoterpene defense strategies in eastern white pine against blue-stain fungi Ophiostoma minus

255th National Meeting (2018)

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