Resin yield in Pinus elliottii Engelm. is related to the resin flow rate, resin components and resin duct characteristics at three locations in southern China

In pine species, resin ducts are the specialized secretory structures to synthesize and store resin. Resin terpenes finds broad applications in pharmaceutical, chemical, biofuel, and food fields. Previous slash pine (Pinus elliottii Engelm.) breeding programs mainly focused on improvements in growth and wood properties in China. The incorporation of resin production into selective slash pine tree breeding occurred rarely, as standard tapping method to identify high-resin yield (RY) individuals is time-consuming, laborious, and expensive. The objective of this study was to identify high-RY slash pine trees with the method of resin flow rate (RFR) in a short timeframe in three plantations of southern China. The comparison of chemical profile between high- and low-yield individuals was also conducted. Moreover, the structural basis referred to resin secretion was studied by investigating the relationship between resin duct characteristics and RY. The phenotypic and genetic correlation coefficients between RY and RFR at all three sites were 0.44−0.85 and 0.58−0.71 respectively, which indicated that RFR measuring technology was reliable for tree breeders to select slash pine trees with high RY for breeding purpose. Resin component analysis revealed that the relative contents of β-pinene were higher in more productive trees; however, for α-pinene, the relative contents were significantly lower. Seasonal variation was low for most resin components and highly consistent across resin yielding classes and test sites. There were strong relations between RY and resin duct size and area at all three sites. High-yield individuals were always characterized by larger duct sizes and larger total areas when compared with low-yield trees. The RFR, certain resin components such as β-pinene, and most resin duct characteristics could be useful criteria for evaluating resin production in slash pine and could be applied to improve tapping management and breeding programs.