First report of Phaeoacremonium viticola affecting grapevines in Spain

A major limiting factor in grape production throughout the world is grapevine trunk diseases (e.g. Eutypa Dieback, Esca, Black Dead Arm, Phomopsis Cane and Leaf Spot) (Pearson, and Goheen, 1988). In 2005, a survey was carried out in North Eastern Spain to determine fungal pathogens associated with such diseases. Symptoms observed during this survey included general decline of vine, internal black wood streaking, central and sectorial necrosis and wood decay. A plant with necrosis around the pith of the trunk, visible in a transverse section was sampled and isolations made. Necrotic material was selected, surface sterilised in 70% ethanol for 1 min, air-dried under sterile conditions and plated onto streptomycin-amended Malt Extract Agar.

Several Phaeoacremonium spp. were isolated. Of these, Phaeoacremonium aleophilum was the most prevalent species. One isolate, however, was identified as P. viticola based on conidiophore and conidia morphology (short and unbranched, often consisting of a single cylindrical phialide of 2-5 um in length; hyaline, obovoid or reniform, 4µm long), and colony colour on malt extract agar (greyish pink). Identity was confirmed by PCR using the species-specific primer pair T1-Pbr8 (Mostert et al., 2006). Pathogenicity of P. viticola isolated from this study was tested by inoculation of 2-month-old pot grown seedlings of Vitis vinifera cv. Malvar. The soil of seven plants was inoculated by drenching with 40 ml spore suspension (10⁷ spores / ml). A further seven control plants were inoculated with 40 ml of sterile distilled water. The plants were maintained in a growth chamber at 24°C and 40 % relative humidity. Symptoms were checked periodically for two months. By the end of the experiment all seedlings inoculated with P. viticola were symptomatic; symptoms ranged from defoliation (four plants with only the apical leaf remaining), crown necrosis (one plant), epinasty (one plant), to death (one plant). Control plants inoculated with sterile water did not show any of these symptoms. P. viticola was re-isolated from the infected plants. Similar symptoms caused by P. viticola have been previously described (Dupont et al., 2000), but this is the first report of the disease in Spain.