Oleoresin characteristics of progeny of loblolly pines that escaped attack by the southern pine beetle

Oleoresin characteristics of first-generation (F-1) progeny of loblolly pines (Pinus taeda L.) that escaped mortality from the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae), despite heavy mortality of neighbors, were evaluated and compared to trees from a general (i.e., trees produced from bulk seed sources) population over the course of two and a half years in southcentral Mississippi (USA). Trees were 21-25 years old and growing in a common-garden type planting when sampled. The relative concentrations of five monoterpenes, five resin acids, and one phenylpropanoid were determined from oleoresin collected on five dates over 18 months. Multivariate analysis of variance showed that the concentration of 11 oleoresin chemical components did not differ between trees from escape and general populations (P > 0.619), providing evidence against the importance of this potential resistance factor. Univariate analyses on three individual resin constituents that were deemed important prior to the study-x-pinene, 4-allylanisole, and limonene-showed that only 4-allylanisole (P < 0.0339) varied significantly between populations; however, its concentration was higher in trees from the general population ((x) over bar = 1.4 vs. 0.9% of oleoresin weight), which does not support the hypothesis that higher concentrations of 4-allylanisole in oleoresin facilitated escape from D. frontalis attack. Oleoresin flow, on the other hand, was significantly higher in escape trees-averaging 1.65 times higher than general population trees over the course of 28 months (eight sampling times). This strongly supports the hypothesis that oleoresin flow can impact the host selection process of D. frontalis, and suggests that increased flow can improve survival under heavy pressure from D. frontalis. These results also may provide an indirect estimate of the magnitude of increase in flow necessary for producing a 'real world' impact on the outcome of the interaction between D. frontalis and a preferred host. (C) 2002 Elsevier Science B.V. All rights reserved.