CONICET | Buscador de Institutos y Recursos Humanos

Phytophthora austrocedri is a straminipilous (heterokonta) organism that causesmortality of Austrocedrus chilensis, an endemic Cupressaceae from the PatagonianAndes forest in temperate South America. This soil pathogen colonizes andkills the roots and extends up to the stem causing necrosis of cambium, phloemand xylem ray parenchyma. An anatomical study of affected tissues was conductedin order to better understand the process of pathogen colonization and tree response. It was found that tracheids of the xylem of affected trees showedlarge numbers of trabeculae, both rod- and plate-shaped. The occurrence of these structures was clearly associated with the necrotic lesion area, since the trabeculae were rare in healthy tissues above the necrotic lesion. Trabeculaeoccurred in a variety of arrangements: solitary or in long files, single, doubleor triple. Our results could indicate that trabeculae proliferation in tracheidsof A. chilensis trees is induced by the stress generated by the P. austrocedriinvasion. Whether this is triggered by a nonspecific stress response or in direct response to the pathogen remains to be tested.