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Diplodia seriata and D. mutila causal agents of gummy canker in Araucaria araucana trees

Ximena Besoain: Pontificia Universidad Católica de Valparaíso

<div>During the last two years a severe decay was observed in <em>Araucaria araucana</em> trees in Araucanía region of Southern Chile and in Valparaíso region of Central Chile. The plants showed arms with dieback symptoms, leaf orange discoloration, canker in the cortex and cream color gummy exudation. In order to determine if these species were responsible for the observed decay two pathogenicity tests were conducted employing 2-year old <em>A. araucana </em>plants (n=3) for <em>D. seriata</em> trial and 10-year old <em>A. araucana</em> plants for <em>D. mutila.</em> Two isolates of <em>D. seriata</em> were recovered from the advance zone of the lesions in southern area (close to Conguillio National park) while two isolates of <em>D. mutila</em> were recovered from the northern area (garden in Quillota city). In both trials plants were inoculated by an injurie and a mycelial plug (8 mm) of each <em>Diplodia</em> species was introduced in a injurie. Three plants were left as controls for each test, employing only a PDA sterile plug (8 mm) in injurie. After two months, the inoculated <em>Diplodia</em> plants showed similar symptoms in both trials, arm dieback, orange discoloration and canker in the branches and cream color gummosis. A first report was previously done for <em>D. mutila</em> causing gummy canker in <em>A. araucana</em>, but this is the first report of <em>D. seriata</em> causing gummy canker of Araucaria trees close to the Conguillio National Park. Both species were molecularly detected analyzing ITS, beta tubulin and elongation factor and deposited in GeneBank.</div>