Resin exudation profile, chemical composition, and secretory canal characterization in contrasting yield phenotypes of Pinus elliottii Engelm

Abstract

In conifer stems, secretory canals synthesize and store resin for defense against herbivores and pathogens. Resin terpenes are used as raw material by an array of industrial sectors. Most forest stands operationally used in resin extraction are derived from seeds, showing high genetic variation, which reflects in yield. The objective of this study was to identify adult slash pine (Pinus elliottii Engelm.) trees of high yield of resin in a short timeframe by resin mass flow rate analysis, aiming at the establishment of elite forests for tapping prior to its start. In addition, the anatomical basis of resin yield was investigated by examining the correlation between parameters such as number, shape, area and internal volume of wood canals with resin production. Monoterpene composition in resin of high and low yielding trees was also compared. The resin flow-based selection method was reliable for resin yield phenotype detection, confirming this property in trees formerly identified as being of high and low resin production by conventional tapping. The reverse test for identification of high and low yield resin features in previously untapped younger plants was in good agreement with their yields after subsequent standard tapping procedure. To evaluate and quantify the three-dimensional structure of resin canals, we used microCT scans. High yielding trees had more axial resin canals when compared with low yielding ones. Frequency of putative anastomosed canals and canal diameter were also superior in the former. Chemical analyses of resin monoterpenes revealed that the ratio of α-pinene/ β-pinene was lower in more productive trees, which also had more limonene in total terpenes compared with their low yield counterparts. Data support the use of short-term resin mass flow rate analysis as a tool to identify and select high yield trees for the establishment of elite slash pine forests for resin tapping operations. Strong correlation of the superesinous phenotype with canal density and structure was also evident.