DETERMINATION OF MONOTERPENES IN OLEORESIN - A CHEMOSYSTEMATIC STUDY OF THE INTERACTION BETWEEN FRASER FIR (ABIES FRASERI) AND BALSAM WOOLLY ADELGID (ADELGES PICEAE)

The Fraser fir (Abies fraseri). a conifer native to high elevation sit es in the southern Appalachians. has suffered severe mortality attribu ted to an exotic insect. the balsam woolly adelgid (BWA) (Adelges pice ae). Fraser fir, like many other plants. produce volatile organic comp ounds called monoterpenes in a variety of tissues, including the corti cal oleoresin found in blisters on the bark. The purpose of this study was to perform a chemosystematic study to evaluate whether difference s in monoterpene composition of Fraser fir oleoresin were observed as a function of the season sampled. the presence or absence of BWA infes tation. the health of a tree, and the susceptibility of trees to BWA b ased on geographic location. Oleoresin was collected in September and December, 1994, at two mountains, Mount Rogers, where the fir were rel atively health and Roan Mountain. where heavy to moderate mortality ha s been observed, The oleoresin samples were dissolved in methylene chl oride. and the monoterpenes were determined by gas chromatography. Thi s method was shown to have acceptable precision for chemosystematic st udies for five monoterpenes and the total of all monoterpenes, The lev els of monoterpenes in oleoresin were statistically the same for most compounds in September and December. although the total monoterpenes w ere higher in September at Mount Rogers and alpha-pinene was higher in December at Roan Mountain. Infested and uninfested fir had the some l evels of oleoresin monoterpenes at both mountains. No differences in m onoterpene levels were observed at Mount Rogers with healthy and unhea lthy fir, but at Roan Mountain, the total monoterpene concentrations w ere different in these categories. A comparison of monoterpene concent rations in oleoresin front Mount Rogers and Roan Mountain showed stati stically significant differences for 3-carene, beta-phellandrene, and total monoterpenes. (C) 1997 Academic Press.