EPPO Global Database

EPPO Reporting Service no. 09 - 2012 Num. article: 2012/191

Seiridium cardinale (cypress canker) probably originates from California (US)

Cypress canker is a destructive disease of Cupressaceae which was first observed in 1928 in California (US) on Monterey cypress (Cupressus macrocarpa). Since this initial report, the disease has been found in most continents, probably transported via trade of ornamental Cupressaceae. During the last 50 years, epidemics have been particularly severe around the Mediterranean Basin on Cupressus sempervirens. There has been considerable debate about the causal agents involved in cypress canker and their taxonomy, and it has been suggested that three distinct species of Seiridium, S. cardinale, S. cupressi, and S. unicorne, were associated with the disease. However, the overall distribution and virulence of S. cupressi and S. unicorne are clearly lower when compared with those of S. cardinale. Therefore, the latter is considered as the major cause of cypress canker. A tentative distribution list of S. cardinale is as follows:
EPPO region: Algeria, Croatia, Cyprus, France, Germany, Greece (including Crete), Ireland, Israel, Italy, Montenegro, Morocco, Portugal, Serbia, Spain, Tunisia, Turkey, United Kingdom (England, Northern Ireland).
Africa: Algeria, Morocco, South Africa, Tunisia.
Asia: Israel, Syria.
North America: Canada (British Colombia), USA (Alaska, California, Oregon).
South America: Argentina, Costa Rica.
Oceania: Australia (Western Australia), New Zealand (North and South Islands).

For many years, it has been supposed that S. cardinale had been introduced from Northern America into other parts of the world, and in particular into the Mediterranean region. A recent study from Della Rocca et al. (2011) supports this hypothesis. A genetic analysis of fungal populations from California, several Mediterranean countries, Chile and New Zealand was carried out, using β-tubulin sequences and 7 polymorphic simple-sequence repeats (SSRs). In total, it included 96 isolates of S. cardinale, as well as β-tubulin sequences (from GenBank) of 8 isolates of S. cardinale, 3 of S. unicorne and 7 of S. cupressi. Results of the sequence analysis identified 2 distinct β-tubulin alleles which were both present in California, but only one of them was found in Mediterranean countries. The analysis of SSRs showed that the genotypic diversity was consistently higher in Californian populations of S. cardinale. These results strongly suggest that California is the most likely source of epidemics in the Mediterranean region, and possibly the area of origin of S. cardinale. This study also confirmed the existence of 3 distinct species of Seiridium. Finally, the authors underline that the fact that the establishment of a single genotype has probably caused the entire Mediterranean infestation also highlights the need to prevent any further introductions of S. cardinale and, in particular, of other genotypes.


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