Resinosis of young slash pine (Pinus elliottii Engelm.) as a tool for resin stimulant paste development and high yield individual selection

Pine resin, a natural source of industrially relevant terpenes, is a major non-wood forestry commodity. Resin is obtained by wounding the bark of adult trees and applying stimulant pastes with different adjuvants on the wound. Identifying new adjuvants and high resin producing trees in adult forests often requires long time and intense labor. Microtapping, i.e. use of young plants of Pinus elliottii var. elliottii cultivated in greenhouse to extract resin, was evaluated as an alternative to carry out these activities. Compounds with known effect in adult plants (ethrel, benzoic acid and potassium sulfate) and molecules involved in the transduction of defense signals (methyl jasmonate, salicylic acid, linolenic acid and isoleucine) were evaluated in young plants. One, two and three-year-old plants consistently increased resinosis when treated with potent adjuvants, mainly methyl jasmonate. The more lignified basal stems produced more resin than apical ones in the 1-year-old plants. Resin yield increased after the second year. All plants were responsive to successive stimuli, just as adult plants. High resin-yield individuals were identified by microtapping, and this phenotype was further supported by terpene-related gene expression studies associated with resinosis. Therefore, microtapping can be used for early, rapid, and simple identification of adjuvants with high resin induction capacity and of putative elite individuals for field evaluation, breeding, and clonal propagation.