Heritability and characteristics of resin ducts in Pinus oocarpa stems in Michoacán, Mexico

Abstract

Abstract Despite the extensive distribution and use of Pinus oocarpa in Mexico, knowledge on the range of genetic variation and magnitude of quantitative parameters of the defensive structures of the species is rare. Our study attempts to fill this gap by providing a comprehensive assessment of resin duct traits in mother trees and their offsprings in an open-pollinated trial of P. oocarpa. Resin ducts are fundamental structures of the defense mechanisms of the coniferous trees. They vary depending on the age of the tree, the genotype, the species, and may be influenced by environmental factors. We investigated intraspecific variation among families of the resin duct system in secondary vascular tissues (wood and inner bark) of P. oocarpa trees. Our study attempts to explore the variance and the possible genetic control of these defensive structures. We hypothesized that the resin duct features analyzed would vary with the tree’s genetic make-up. We analyzed samples from two groups of trees. First, from mature mother trees selected as superior in resin yield. Second, from their six-year-old off-springs established in a progeny trial. Axial and radial ducts showed differences in their size and quantity, between wood and bark and between ages. The axial duct density showed differences among families, and the heritability estimates were moderate. In P. oocarpa trees selected as phenotypically superior in resin yield, the size of its constitutive resin ducts is a less variable trait, and the differences in axial duct density can be attributed to genetic factors.