First outbreak of Citrus tristeza closterovirus near Siracusa, Sicilia (IT)
During surveys for the selection of superior old citrus lines done near Siracusa (Sicilia, Italy), trees in several blocks of mandarin (Citrus reticulata cvs. Fortune, Nova), Satsuma (C.unshiu) and grapefruit (C. paradisi cv. Marsh) showed stunting, decline, dieback, reduction of fruit size, and often pinholing near the bud-union line. As these symptoms are often associated with Citrus tristeza closterovirus (CTV - EPPO A2 quarantine pest), further tests were done. Young shoots were collected from 600 Fortune, 300 Nova, 400 Satsuma and 20 Marsh grapefruit, and tested by DAS-ELISA and immunoprinting ELISA using CTV polyclonal antibodies. All samples tested positive. Total RNA was extracted from 50 of these plants (25 Fortune, 15 Nova, 5 Satsuma, 5 grapefruit) and tested by RT-PCR. The presence of CTV was confirmed.
Studies were done to trace the history of plants growing in the affected blocks. All trees had been propagated from budwood most probably infected which had been illegally imported from Spain 10 years ago. It is estimated that in the area of Siracusa approximately 10,000 trees are now infected, with some evidence suggesting that natural spread is occurring. Additional surveys are being done better to estimate the incidence of the disease, to verify its dissemination by aphid vectors and to characterize virus strains present in the area.
Previously, only scattered CTV-infected trees have been detected in Italy. Therefore this is the first report of a significant outbreak in a citrus-growing area. It is felt that CTV represents a major threat to the Italian citrus industry. It is recalled that, in Sicilia, citrus is grown on 100,000 ha mostly on susceptible sour orange rootstocks.
The situation of Citrus tristeza closterovirus in Italy can be described as follows: Present, found in the area of Siracusa, Sicilia. In other parts of Italy, it has been found erratically and is not established. Under official control.
Sources
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Davino, S.; Davino, M.; Sambade, A.; Guardo, M.; Caruso, A. (2003) The first Citrus tristeza virus outbreak found in a relevant citrus producing area of Sicily, Italy.
Plant Disease, 87(3), p 314.
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