Resin defense in Pinus–Fusarium circinatum interactions: an evolutionary paradox

Resin has long been a vital part of conifer defense, providing both physical and chemical protection against pests and pathogens. This assumption gives rise to an evolutionary paradox: why do some pine species that produce more resin and larger resin ducts remain vulnerable to disease? Fariña-Flores et al. (2026) examined this question by comparing the response of resistant Pinus pinaster and susceptible P. radiata following infection with Fusarium circinatum. Resin-based defences are generally considered protective; however, their results suggest that under certain conditions they may be associated with increased vulnerability rather than consistent effective resistance.