The current status of the quick decline syndrome of olive in southern Italy
The quick decline syndrome of olive (OQDS) is a disease that appeared all of a sudden some years ago in a restricted area near the city of Gallipoli (Ionian coast of the Salento peninsula, southern-east Italy) and began spreading through the heavily olive-grown countryside of lower Salento. Xylella fastidiosa, a quarantine pathogen of American origin previously undetected in the European Union territory, except for two unconfirmed records from Kosovo and Turkey, proved to be consistently associated with symptomatic trees. X. fastidiosa is a Gram-negative bacterium that invades and multiplies in the xylem vessels of infected hosts, from which it is acquired by xylem-feeding insect vectors (belonging to Auchenorrhyncha, including cicadellids sharpshooter leafhoppers group, Cicadellidae, Cicadellinae), and aphrophorids (cercopids and spittlebugs, Cercopidae) and transferred to other plants. The Salentian strain of X. fastidiosa, denoted CoDiRO, was obtained in axenic culture. Its genome, a DNA molecule ca. 2.5 million base-pairs in size, was sequenced and identified as a genotype of X. fastidiosa subsp. pauca molecularly identical to an isolate of the same subspecies from Costa Rica. In nature, strain CoDiRO infects a number of woody and shrubby hosts but not grapevines and citrus and is mainly transmitted by Philaenus spumarius (meadow spittlebug), a froghopper quite common in the Salento area where it thrives primarily on olive. Since OQDS eradication and sanitation of infected olives are unfeasible, strategies have been envisaged for restraining the spread of the pathogen and its vector within the boundaries of the currently infected zone.