A new Phytophthora from Austrocedrus trees with symptoms of “Mal del ciprés” in the Patagonian Andes of Argentina.

GRESLEBIN, ALINA G.; HANSEN, EVERETT M.

Québec, Canadá

Congreso; American Phytopathological Society Joint Meeting; 2006

American Phytopathological Society

Austrocedrus chilensis, an indigenous conifer of the Andes similar to the North American incense cedar, suffers in many parts of its range from a locally dramatic but unexplained disease. The distribution and pattern of spread of mortality in a stand is consistent with a soil-borne pathogen, and association with seasonally poorly drained soils has led several workers to suggest that a Phytophthora species might be responsible. Symptoms include basal resinosus and red-brown necrotic inner bark extending up the bole from killed roots. Initial isolations from lesion margins using Phytophthora-selective media failed, but an ELISA test on necrotic phloem tissues was positive for Phytophthora, and subsequent DNA extraction from necrotic bark and amplification of ITS DNA using Phytophthora-specific primers was successful. Thus encouraged, isolation attempts were renewed and were finally successful. The new species, provisionally named P. “austrocedrae,” is homothallic with amphigynous antheridia and semi-papillate sporangia. It is very slow growing, with optimal temperature near 15C. It takes 10 days or more before first growth from bark pieces is visible on selective media. ITS DNA sequence places it near P. syringae in phylogenetic clade 8 of the genus. Pathogenicity tests are underway.