First report of Phomopsis asparagi causing stem blight of asparagus in Greece

Abstract

Severe stem blight of asparagus (Asparagus officinalis) was found in western Greece in early October 2003. Elongated, oval-shaped, 0·5–5-cm-long lesions were formed on the stems, starting as light brown lesions that later turned dark reddish brown. The central tissue was pale in colour, and pycnidia appeared on old lesions. The disease was found on leaves and any part of the stem. More lesions occurred on the stem base than on the upper parts of the plant. Cladodes became yellow and later brown until complete desiccation and stem death occurred as a consequence of the disease. Fungal isolates were obtained from diseased tissue on potato dextrose agar. Black pycnidia, 250–500 × 185–300 µm, were produced with straight, hyaline conidiophores and hyaline conidia 6·5–10 × 2–3 µm. According to the morphological characteristics the fungus was identified as Phomopsis asparagi (Uecker & Johnson, 1991). Pathogenicity tests were performed on 4-month-old plants of the asparagus hybrid cv. Steline. Two Phomopsis isolates and seven plants per isolate were used. A suspension of 106 conidia mL−1 was sprayed onto the plants, which were incubated at 25°C for 2 days in polyethylene bags. Control plants were sprayed with sterile water. Six days after inoculation the first symptoms appeared on stems and leaves. Symptoms were identical to those observed in young infections in the field. The inoculations were repeated by placing mycelial plugs on the stems, and the results were the same. No disease was produced on control plants. The fungus is known in America, Europe, Asia and Southern Australia, and reported as Phoma or Phomopsis asparagi causing stem blight, fern defoliation and subsequent yield loss, particularly in humid areas (Reifschneider & Lopes, 1982; Sherf & Macnab, 1986; Davis, 2001). Asparagus is an economically important crop in Greece, where the growing areas, particularly in the western part of the country, are characterized by humid, disease-conducive conditions during the growing season. This is the first report of P. asparagi causing severe stem blight on asparagus in Greece. I wish to thank Ms Sofia Migardou for her excellent technical assistance.