ABSTRACT Brown‐spot needle blight (BSNB) and Dothistroma needle blight (DNB), caused by Lecanosticta acicola and Dothistroma septosporum , respectively, are foliar fungal diseases threatening pine forests worldwide. They impact natural ecosystems, plantations and nurseries, with risks expected to intensify under climate change and global plant trade. Although caused by different pathogens, BSNB and DNB have similar symptoms, complicating diagnosis. To understand host–pathogen interactions, we investigated physiological and biochemical host responses that may help differentiate these diseases. We studied three ecologically and economically important pine species— Pinus radiata , P. pinaster and P. pinea —after needle inoculation with both pathogens under controlled conditions. At 115 days post‐inoculation, symptomless needles from infected plants and controls were analysed for systemic response, including growth, gas exchange, primary and secondary metabolites profiles and malondialdehyde (MDA), as a stress biomarker. While both pathogens induced similar visible symptoms, host responses were distinct. In P. pinea , L. acicola reduced photosynthetic pigment content (PHP) and photosynthesis, whereas D. septosporum only affected PHP. Both pathogens triggered defence‐related metabolic adjustments, including reduced growth, increased total phenolic compounds (TPC) and MDA. In P. pinaster , D. septosporum lowered TPC and MDA, while L. acicola decreased PHP. P. radiata maintained growth, while reducing MDA levels. These findings highlight that similar symptoms can conceal contrasting, species‐specific host responses. Understanding these differences is essential and highlights the need for molecular studies to identify early detection biomarkers that can differentiate BSNB from DNB, as host metabolic responses offer promising yet underexplored potential for advancing sustainable disease management in forest protection.
Monteiro et al. (Thu,) studied this question.