Findings of American plum line pattern ilarvirus in Europe
During a survey on stone fruit viruses conducted in Palestine, an unusual virus was isolated from Prunus salicina cv. Beauty. Mechanical inoculation to herbaceous indicators (Nicotiana occidentalis) produced symptoms but ELISA tests failed to detect ilarviruses and nepoviruses known to occur in fruit trees in Europe. Further studies (biological characterization, virus purification, partial sequencing, molecular hybridization and serology) revealed the presence of American plum line pattern ilarvirus (APLPV - EPPO A1 quarantine pest). This finding prompted investigations in other countries. A total of 701 samples was collected from 13 Italian commercial plum orchards, 3 varietal collections (Italy and Spain), and the virus-infected stone fruit collection of IAM-Bari (IT). Samples were tested by ELISA, and if positive, re-tested by molecular hybridization. All samples from commercial orchards (516) and varietal collections (170) gave negative results. Out of the 15 re-tested samples, APLPV was detected in 4 samples of P. salicina grown in the virus-infected collection of Bari. These samples originated from Italy (Puglia and Sicilia), Albania and Tunisia. All APLPV-infected plants were collected as symptomatic samples during previous surveys but had not been specifically tested for the presence of this virus. More extensive surveys are under way to assess the incidence of APLPV in the Mediterranean region.
Concerning the Tunisian situation, the NPPO of Tunisia provided more information and stated that the infected samples had been collected from 2 trees (P. salicina cv. Sciro) during the 1995/96 growing season) in a commercial apple orchard (and not a plum orchard) in the region of Mornag (20 km south of Tunis). Trees located in the vicinity of this orchard were all apple and pear which are not hosts of APLPV. In addition, the Japanese plum cultivar concerned (cv Sciro) is not included in the Tunisian list of registered varieties. Therefore, it is concluded that these infected Japanese plum trees had been illegally introduced into Tunisia and later destroyed (even before APLPV tests were done). Visual inspections were carried out in all commercial orchards in the region of Mornag, and failed to detect any APLPV symptoms.
Concerning the Italian situation, the NPPO of Italy provided more information. The sample from Puglia corresponded to an old case. In 1992-93, a plant showing suspect virus symptoms was discovered. As the orchard was old, it was uprooted but a budstick was kept at the IAM-Bari and tested many years afterwards. Present surveys being carried out in Puglia, and the nearby region Basilicata, failed to detect symptoms of APLPV. The other sample from Sicilia was collected in autumn 2002 from a small plum orchard, on a tree which showed symptoms. A survey is planned in 2003 to delimit better the extent of the disease in Sicilia.
Concerning the Albanian situation, the NPPO of Albania stated that no further information is yet available on the possible presence of APLPV, and that surveys will be carried out in 2003.
Although, more studies are needed to understand better the current situation of APLPV in Europe, it appears that this North American virus is present in at least in some parts of the EPPO region.
Sources
Alayasa, N.; Al Rwahnih, M.; Myrta, A.; Herranz, M.C.; Minafra, A.; Boscia, D.; Castellano, M.A.; Pallás, V. (2003) Identification and characterization of an American plum line pattern virus isolate from Palestine.
Journal of Plant Pathology, 85(1), 3-7.
Myrta, A.; Abbadi, H.; Al Rwahnih, M.; Herranz, M.C.; Di Terlizzi, B.; Minafra, A.; Pallás; V. (2002) First report of American plum line pattern virus in Albania, Italy and Tunisia.
Journal of Plant Pathology, 84(3), 171-200.
NPPO of Albania, 2003-02.
NPPO of Italy, 2003-01.
NPPO of Tunisia, 2003-02.