Multivariate detection of hybridization using conifer terpenes II: Analysis of terpene inheritance patterns in Pseudotsuga menziesii F1 hybrids

The compositions of the volatile leaf oils of Pseudotsuga menziesii var. menziesii and var. glauca and their hybrids were examined and utilized to examine multi-variate methods for the detection of hybridization. The first cross (coastal parent 226 x inland parent 267) produced four hybrids whose oils were much like the inland (var. glauca) parent, and 6 hybrids with composition more intermediate between the parents. Eleven of the terpenes were generally intermediate in the hybrids, whereas the other 15 terpenes were transgressive. Truncation of the terpene values to those of the maximum or minimum value of the parents improved PCO ordination using character weights of Fs from ANOVA. A second set of hybrids between coastal parent 517 x intermediate parent 521 yielded similar kinds of variation in the terpenes of the hybrids. Only 2 compounds were intermediate between parents whereas 8 terpenoids showed dominance with values like one of the parents. Nine of the terpenes and percent oil yield were transgressive to both parents. Using F weighting and truncation of transgressives, improved the ordination separating parents from hybrids. However, again, the hybrids were ordinated in two groups. Selecting a balanced set of discriminating terpenes, aided in ordination. In a study of natural field hybridization, the terpenes should be useful to classify the hybrids, but it may be difficult to accurately classify back-crossed or F2 individuals. Published on-line: www.phytologia.org Phytologia 95(1): 42-57 (Feb. 1, 2013).