Partial ribosomal DNA sequences show an important divergence between Phaeoacremonium species isolated from Vitis vinifera

A morphological and molecular analysis was performed on 25 individuals of Phaeoacremonium isolated from diseased European and Californian grapevines (Esca disease). An unexpectedly high intra-generic molecular divergence was evidenced by partial rDNA sequencing between P. chlamydosporum isolates on one hand and an aggregate including P. angustius and P. aleophilum isolates and some undescribed ones on the other. These two groups show 26% nucleotide differences within the 26S rDNA fragment sequenced and were unalignable within the ITS2, suggesting distant phylogenetic relationships. Moreover, P. chlamydosporum appeared more closely related to Phialophora verrucosa (supposed to be an anamorph of the Herpotrichiellacae), than to the type species of the genus, P. parasiticum (more related to Magnaporthaceae).