First Report of Occurrence of Potato Tuber Necrotic Ringspot Disease in Greece.

Potato tuber necrotic ringspot disease (PTNRD), caused by potato Y potyvirus isolate NTN (PVYNTN) of the N virus strain group, was first described in Hungary in 1980. It has spread throughout Europe, with the most recent reports from Portugal and Italy in 1997 to 1998 (1). Superficial necrotic ringspot areas on tubers, typical of PTNRD, were first observed in commercial potato fields of the Nevrokopi region in northern Greece in 1994. Affected cultivars included Timate and, to a lesser extent Spunta, the original seed of which came from the Netherlands. PVY was identified from all tubers tested by indexing on Nicotiana tabacum and subsequent testing of the plants by double antibody sandwich-enzyme-linked immunosorbent assay (DAS-ELISA). The potato seed lots were rejected by the local authorities. PTNRD reappeared in the same area in 1998 in a more aggressive manner. Cultivar Hermes, imported from Scotland, was most affected, with very severe symptoms in 80% of the tubers. Symptoms appeared in early September, 40 days after defoliation of the plants. Other cultivars were affected at lower rates; cv. Spunta showed typical symptoms and cvs. Fabola, Santana, and Irvila exhibited atypical cracks and blisters. In all cases, PVY was isolated in N. tabacum and its presence confirmed by DAS-ELISA. Immunocapture-reverse transcription-polymerase chain reaction with specific PVYNTN primers (2) detected the characteristic 835-bp product in all cultivars tested. The incidence of PTNRD seems to be expanding in northern Greece, where it has become a threat to potato production. PTNRD symptoms were also observed in southern Greece (Ahaia) in experimental "crossing" fields of seed stocks. In this case, the disease seems to have spread especially in cv. Marfona. References: (1) L. Tomassoli et al. Plant Dis. 82:350, 1998. (2) H. L. Wiedemann and E. Maiss. Z. Pflanzenkrankh. Pflanzenschutz 103:337, 1996.