Effect of Pinus pinaster and Pinus radiata resin on biomass growth of Fusarium circinatum

Pines produce and accumulate oleoresin, which is part of the preformed defensive system or is synthesized de novo in response to biotic and abiotic challenges. Fusarium circinatum is a fungal pathogen that causes Pine Pitch Canker disease and is characterized by cankers with abundant resin at the infection site. F. circinatum colonizes the plant using both constitutive and traumatic resin ducts, indicating a resin tolerance that needs to be evaluated. Using a spectrophotometric technique, we assessed the effects of constitutive and induced resin on the growth of F. circinatum. The pathogen was grown in minimum medium supplemented with resin (at 0.8, 1.5 and 3 % concentrations) in the wells of a microplate for 6 days, and the absorbance at 570 nm was measured as an indicator of fungal biomass. The results showed that resin from Pinus pinaster and Pinus radiata enhanced fungal growth, as the absorbances measured with the addition of volatile or nonvolatile fractions extracted from constitutive and induced resins increased above 100 % relative to the solvent used in resin extraction. F. circinatum grew 40 % more in the hexane extract of the induced resin than in the constitutive resin of P. radiata. Terpene profiles determined by GC-MS analysis differed quantitatively and qualitatively by resin type (constitutive or induced) and pine species. The F. circinatum growth with various single terpene components of resin at different concentrations was also measured. The absorbance results showed that α-pinene and citronellol (monoterpenes) promoted growth at specific concentrations, while all others inhibited or did not affect it.