Occurrence of grapevine leaf spot caused by Pseudocercospora vitis in Argentina

In the lowland, coastal region of Berisso (in the north-east of Buenos Aires Province), family farmers cultivate American grapevine (Vitis labrusca) for the production of a typical 'coast wine'. In this region diseased plants were observed and affected leaves sampled. Leaf spots were circular, amphigenous, sometimes confluent, 2-8 mm in diameter, brown or purplish brown (Fig. 1). Pseudocercospora vitis, the anamorph of Mycosphaerella personata, was consistently isolated from diseased material. The spore morphology of the specimen agreed with that of P. vitis as described by Ellis (1971). Conidia were 5-10 septate, 25-90 µm long and 5-8 µm wide. The identity of the isolate was confirmed by Dr U. Braun, Martin-Luther Universität, Germany (Accession number HAL 1755).

For pathogenicity tests, nine grapevine plants were grown for a year in 10-litre pots in the greenhouse. Two treated plants and an untreated control plant were used for each of three replications. Each treated plant was sprayed with a conidial suspension of HAL 1755. Controls received only distilled water. After twenty days incubation, the original leaf spot symptoms were reproduced and P. vitis was recovered from these lesions. No symptoms appeared on the control plants.

Several genera of Vitaceae (Ampelopsis, Cissus, Parthenocissus) and different species of Vitis are listed as hosts of P. vitis (Farr et al., 1989). Pseudocercospora vitis has been found in Brazil, Europe, India, Japan, North America, Korea, Pakistan, Saudi Arabia and South Africa (Ellis, 1971; Shin, 1997). Pseudocercospora vitis was reported in Argentina on European grapevine (V. vinifera) almost a century ago but no symptoms were described (Spegazzini, 1910). In the lowland regions of Berisso, where American grapevine is grown, the relative humidity is high; partly due to the influence of La Plata River. Pathogen infection is favoured by high humidity and therefore the disease constitutes a potential problem for American grapevine in the specific cropping areas where it is grown. In other regions of Argentina, where European grapevine is grown extensively, the precipitation is increasing because of climate changes. Grapevine leaf spot may become a future threat to this economically very important crop. This is the first record of grapevine leaf spot on V. labrusca and on any host in Argentina.