Detection and molecular characterization of viruses infecting Actinidia spp.

Kiwifruit (genus Actinidia) is an economically important crop, with an industry in continuous expansion, grown in temperate regions. Italy (415,000 tons), New Zealand (378,000 tons) and Chile (229,000 tons) are the world’s largest producers with a harvested area of 25,000, 12,800 and 10,900 Ha, respectively. In Italy the main areas of kiwifruit production are localized in Lazio, Piedmont, Emilia Romagna and Veneto regions. More than 50 species are recognized in the genus Actinidia but in New Zealand and Italy A. deliciosa and A. chinensis are the most widely grown cultivars¬¬. Kiwifruit has been considered to be relatively disease free for more than 30 years however, since 2003, several viruses and virus-like diseases have been identified and more recent studies demonstrated that Actinidia spp can be infected by a wide range of pathogens. Currently eleven different viral species have been identified on kiwifruit plants. In order to evaluate and prevent potential risks related to viral diseases spreading, several studies to investigate the presence of viruses on kiwifruit orchards and nurseries have been initiated. Kiwifruit plants showing symptoms attributable to viral infection, as yellow mosaic, chlorotic or necrotic rings, curled or laciniated leaves and wood pitting, have been identified during inspection of commercial orchards in the Emilia Romagna region. Suspected samples were collected and analyzed in order to determine the etiology of the observed symptoms. In this work we describe identification and characterization of two viral species: Cucumber Mosaic Virus (CMV) and Pelargonium zonate spot virus (PZSV) from kiwifruit plants showing, respectively, yellow mosaic and chlorotic ring spots. Moreover transmission electron microscopy of partially purified extracts from kiwifruit plants showing laciniated leaves and wood pitting, detected both rod-shaped and flexuous virus particles. Large-scale sequencing of collected samples, for molecular characterization of new viral isolates using next generation sequencing platforms as Ion Torrent, is also presented