Phaeomoniella chlamydospora: causal agent of vine decline (Vitis vinifera) in the vineyards of Slovakia

Symptoms of grapevine decline were first observed sporadically during the 2003 season in the main growing region of Slovakia, Small Carpathian; 23 km away from Bratislava and 55 km around Nitra (17°4' - 18° 3' East; 49°2' - 49° 5 ' North). By the 2005 season disease losses became of notable economic importance. The disease was present in newly established 1-3 year-old vines, as well as older vineyards.

In the newer plantings the disease symptoms observed were stunted growth, small discoloured leaves, reduced trunk caliper and root system, with poor vine establishment in the first year, followed by continued slow growth and eventual loss of plants in subsequent years. Older grapevines (4-5 years) also exhibited foliar symptoms (Fig. 1). In all examined plants, dark brown to black spots were observed in a cross section of the basal rootstock, while in longitudinal section discoloured streaks, located mainly at the basal end of the rootstock and at the graft union (Fig. 2), were observed. Small fragments (approx. 5×2×20 mm) of affected wood tissues (bark removed) were taken to the laboratory and samples deposited in the Institute for Viticulture and Enology, Bratislava.

The slices of wood were surface sterilized, transferred to Petri dishes containing malt agar amended with streptomycin (0.5 mg ml^-1) and incubated in the dark at 25 ±2°C (12-14 days). In culture, the fungal mycelium was branched, tuberculation, hyphae septate with darker septa. Conidiophores were septate, erect, with elongate-ampliform apical cells. Based on the disease symptoms, cultural characteristics and morphology, the fungus was identified as Phaeomoniella chlamydospora (Crous & Gams, 2000; Gatica et al. 2000; Oliveira et al. 2004) (Fig.3).

Koch's postulates were performed under laboratory conditions using one-year-old rooted cuttings of cv. Cabernet Sauvignon (Fig. 4). Twenty microliters of a 1 x 10 spores per ml suspension was injected into the tissue and sealed with sheet of Parafilm. Control plants were inoculated similarly with sterile water. The symptoms observed in the vineyard were reproduced in the inoculated test plants and the pathogen was reisolated from the basal wood. No symptoms were observed on the control plants and no pathogen was isolated from soil. This is the first report of Phaeomoniella chlamydospora causing vine decline in the vineyards of Slovakia.