Characterization of Seiridium spp. associated with cypress canker based onbeta-tubulin and histone sequences

Cypress canker is a serious disease that has devastated Cypressus spp. in m any parts of the world. In Mediterranean Europe it has caused the deaths of millions of trees. Three species of Seiridium, S. cardinale, S. cupressi, and S. unicorne, are associated with cypress canker. Considerable debate su rrounds the taxonomic status of these fungi. They have been viewed as a sin gle morphologically variable species, three distinct taxa; or two species b ased on the presence or absence of conidial appendages. Studies based on ri bosomal DNA (ITS1, ITS2, and 5.8S gene) sequence failed to separate the cyp ress canker fungi. In an attempt to distinguish between the species associa ted with cypress canker we used histone and partial beta -tubulin sequences of fourteen isolates of Seiridium spp. from cypress. Analysis of sequence data showed Seiridium isolates from Cupressus spp., residing in two major c lades. One clade accommodated S. unicorne isolates from Portugal and South Africa. The other major clade consisted of two sub-clades containing non-ap pendaged S. cardinale isolates. We believe the larger second clade, represe nts the cypress canker pathogens while the other clade contains the less pa thogenic S. unicorne, which has a host range beyond Cupressus. This study t hus provides strong evidence to support previous morphological data suggest ing three distinct species are associated with cypress canker.