ARI REVIEW FOR 2016-2017

Production and maintenance of grapevine healthy plant material Efficient control of plant virus, virus-like and prokaryotic diseases starts with the use of healthy propagating material which is free not only from disease symptoms but also from latent infections. EU has recently imposed strict directives on distribution of grapevine material that involve phytosanitary testing of plants for several plant pathogens. Utilisation of healthy plant material seems nowadays the most promising tactic that can ensure good results to control these diseases. During the past decades, ARI has established a long term project on the maintenance of healthy propagative grapevine material under “pre-basic” status. Approximately 70 local or imported varieties are maintained under insect proof net houses at Zygi experimental station. These plants are annually tested for a number of plant viruses including Grapevine fan leaf virus , Grapevine fleck virus , Arabis mosaic virus and Grapevine leaf roll associated viruses 1 and 3, viroids and several other prokaryotic pathogens. Tests are performed using pathogen specific serological and molecular based laboratory techniques. Virus-free grapevine plant cuttings then given to the Department of Agriculture for further multiplication and distribution to Cypriot farmers. ( L.C. Papayiannis, T. Kapari-Isaia ) Epidemiology and evolutionary studies of criniviruses associated with cucurbit yellows disease Cucurbit yellow stunting disorder virus (CYSDV), Cucurbit chlorotic yellows virus (CCYV) and Beet pseudoyellows virus (BPYV) are three whitefly transmitted viruses classified within the genus Crinivirus of the family Closteroviridae . They cause similar yellowing symptoms in cucurbits and are responsible for high economic losses. In nature, CYSDV and CCYV are transmitted by Bemisia tabaci Gennadius, whereas BPYV by Trialeurodes vaporariorum Westwood. An extensive study was conducted in order to identify the virus species involved in interveinal leaf yellowing symptoms, leaf brittleness and plant vigor reduction of plant species of the Cucurbitaceae family in Greece mainland, the islands and Cyprus. In addition, a number of weed samples from the surroundings of the symptomatic surveyed crops, as well as whiteflies were also collected in order to assemble epidemiological data. Results showed that both in the mainland and the islands of Greece, CYSDV was the most widespread virus, followed by CCYV and BPYV. B. tabaci complex and T. vaporariorum species occurrence was evenly distributed. In Cyprus, CYSDV was the predominant virus, followed by CCYV. Both viruses are transmitted only by B. tabaci . Approximately 15% of weed samples from 17 different species which belong in 12 botanical families were identified as hosts for one or more of these criniviruses. Finally, sequence analysis of the capsid protein gene of the crinivirus isolates revealed very low levels of genetic diversity further supporting the genetic stability of Crinivirus populations. ( C.G. Orfanidou, L.C. Papayiannis, P. Pappi, V.I. Maliogka, N.I. Katis ) 45 Plant Protection