Diversity ofPhytophthoraspecies from declining Mediterranean maquis vegetation, including two new species,Phytophthora crassamuraandP. ornamentatasp. nov.

The Mediterranean basin is recognized as a global biodiversity hotspot accounting for more than 25,000 plant species that represent almost 10% of the world’s vascular flora. In particular, the maquis vegetation on Mediterranean islands and archipelagos constitutes an important resource of the Mediterranean plant diversity due to its high rate of endemism. Since 2009, a severe and widespread dieback and mortality ofQuercus ilextrees and several other plant species of the Mediterranean maquis has been observed in the National Park of La Maddalena archipelago (northeast Sardinia, Italy). Infected plants showed severe decline symptoms and a significant reduction of natural regeneration. First studies revealed the involvement of the highly invasive wide-host range pathogenPhytophthora cinnamomiand several fungal pathogens. Subsequent detailed research led to a better understanding of these epidemics showing that multiplePhytophthoraspp. were involved, some of them unknown to science. In total, ninePhytophthoraspecies were isolated from rhizosphere soil samples collected from around symptomatic trees and shrubs includingAsparagus albus,Cistussp.,Juniperus phoenicea,J. oxycedrus,Pistacia lentiscusandRhamnus alaternus. Based on morphological characters, growth-temperature relations and sequence analysis of the ITS andcox1 gene regions, the isolates were identified asPhytophthora asparagi,P. bilorbang,P. cinnamomi,P. cryptogea,P. gonapodyides,P. melonis,P. syringaeand two new Clade 6 taxa which are here described asP. crassamurasp. nov. andP. ornamentatasp. nov. Pathogenicity tests supported their possible involvement in the severe decline that is currently threatening the Mediterranean maquis vegetation in the La Maddalena archipelago.