Morphological and molecular identification of foliar pathogenic fungi of Hevea brasiliensis in Costa Rica

Plantations of Hevea brasiliensis are vulnerable to a wide range of foliar fungal pathogens capable of causing substantial damage throughout the forest rotation cycle. This issue is particularly critical in Costa Rica, where the commercial cultivation of H. brasiliensis is a recent development, and no prior records exist of foliar pathogens affecting this species, thereby limiting timely detection and effective management. The study evaluated the pathogenicity of foliar fungi associated with H. brasiliensis through combined morphological and molecular characterization. Twenty plantation trees (2–4 years old) showing symptoms such as wilting, chlorosis, yellowing, partial to complete necrosis, punctate lesions, and anthracnose were sampled. Fungi were isolated from symptomatic leaves, cultured on potato dextrose agar supplemented with antibiotics, and identified based on colony and conidial morphology, complemented by sequencing of the internal transcribed spacer region (ITS4–ITS5). Pathogenicity was assessed by inoculating healthy detached leaves with mycelial discs from each isolate. A total of 30 isolates were obtained, representing the families Botryosphaeriaceae, Diaporthaceae, Nectriaceae, Apiosporaceae, and Glomerellaceae. Four species were confirmed as pathogenic: Diaporthe tulliensis, Nigrospora sphaerica, Fusarium equiseti , and Lasiodiplodia theobromae . All produced necrotic lesions, with F. equiseti and N. sphaerica generating the largest affected areas. Accurate identification of foliar pathogens is crucial for early disease diagnosis, which supports the development of targeted management strategies and safeguards the long-term health and productivity of H. brasiliensis plantations in Costa Rica.