Monoterpene Content of Healthy Sand Pine and Sand Pine with Root Disease
Graft combinations with slash pine (Pinus elliottii Engelm.) alone and with sand pine (P. clausa var. immuginata D. B. Ward, Choctawhatchee sand pine) were studied to determine if monoterpene content of rootstocks of healthy and diseased grafts is related to susceptibility to root infection. The amount and composition of monoterpenes in branches, scions, rootstocks (stem of the rootstock) and roots were determined for the following graft (scion/rootstock) combinations: healthy and diseased sand/sand, sand/slash, and healthy slash/slash grafts. Buds from the same grafts were analysed for monoterpene composition only. Similar analyses were made of xylem tissue at dbh of healthy and diseased Choctawhatchee and Ocala sand pines (P. clausa var. clausa [Chapm.] Vasey) growing in natural stands. In seed orchard samples, the quantity of monoterpenes was higher in roots and rootstocks of diseased grafts than of healthy grafts. However, monoterpene composition in healthy and diseased grafts was similar within the sand/sand grafts and within the sand/slash grafts. No consistent differences in monoterpene composition were found between these two graft combinations, There was a significantly lower amount of -phellandrene and a higher amount of -pinene in roots and rootstocks of healthy and diseased sand/slash grafts as compared to healthy slash/slash grafts. The roots and rootstocks of slash/slash grafts were not infected by the root disease that is affecting sand pine. Of the trees sampled, sand and slash grafts with low -phellandrene content in the roots and rootstocks were susceptible to root infection. Slash pine grafts with high -phellandrene were not infected. In stem xylem samples from natural stands, no monoterpene differences were detected between healthy and diseased Ocala sand pine. Between varieties, the amounts of several monoterpenes found in both Choctawhatchee and Ocala sand pines differed very little and inconsistently. Forest Sci. 29:791-797.
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