ARI REVIEW FOR 2016-2017

Host range and transmission properties of Begomovirus species involved with tomato yellow leaf curl disease An epidemiological study was conducted in order to investigate the host plants and the potential role of the whitefly vector Bemisia tabaci in the transmission of the Begomovirus species involved in the Tomato yellow leaf curl disease (TYLCD). For this purpose, the host range of two Tomato yellow leaf curl virus (TYLCV) strains (IL and MLD) and one Tomato yellow leaf curl sardinia virus (TYLCSV) isolate was studied using whitefly transmission tests in several plant species. Transmission efficiency of TYLCV and TYLCSV was evaluated using four B. tabaci colonies which belonged to the B and Q biotype. The transmission capacity from alternative infected plant hosts to tomato was also studied. Transmission studies showed that TYLCV isolates had a broader host range as well as higher transmission efficiency than TYLCSV (66,3 and 61,2%, respectively). Moreover, TYLCV transmission was somehow correlated with the presence of Hamiltonella sp., inside B. tabaci insect, as colonies that harbored this bacteria, showed higher transmission rates to tomato plants (68,2 and 71,2%) than colonies that did not harbored Hamiltonella sp. (21,2 and 18,6%). At the same time, higher densities of viruliferous whiteflies showed increased transmission rates. Finally, transmission assays from infected secondary hosts, including weeds and other cultivated plants onto tomato, showed that these alternative hosts could serve as important virus reservoirs, contributing significantly to disease outbreaks. ( L.C. Papayiannis, N.I. Katis ) Incidence of Apis mellifera viruses in Cyprus In collaboration with the Center of Beekeepers and the Department of Agriculture a new research activity was performed in order to investigate the presence of bee viruses in Cyprus. More than 100 apiaries from the districts of Nicosia, Lemesos, Larnaka, Pafos and Ammochostos were surveyed and approximately 35 adult bees per apiary were randomly collected and stored at -80 °C. A total of 1870 samples were tested for virus presence using molecular based techniques and results showed that Black queen cell virus (BQCV) was the most widespread virus with an incidence of 88%, followed by Deformed wing virus (DWV) which was detected in 31%. Acute bee paralysis virus (ABPV) and Varroa destructor virus -1 (VaDV-1) were also identified at a very low incidence of 3 and 2% respectively. DWV, ABPV and VaDV-1 were found in mixed infections with BQCV. Kashmir bee virus (KBV), Chronic bee paralysis virus (CBPV) and Sacbrood bee virus (SBV) were not detected. ( L.C. Papayiannis, Y. Markou, A. Aggeli ) First report of Cucurbit chlorotic yellows virus (CCYV) Cyprus In 2016, an outbreak of a yellowing disease causing chlorosis and interveinal chlorotic spots on lower leaves was observed in open field cucumber ( Cucumis sativus ), melon ( C. melo ) and watermelon ( Citrullus lanatus ) plants in Nicosia and Limmasol Districts. These symptoms were similar to those caused by whitefly transmitted Criniviruses as well as aphid transmitted Poleroviruses. Leaf samples were collected and total RNA was extracted and tested for the presence of several viruses using RT-PCR. Results showed that plants were simultaneously infected Cucurbit yellow stunting disorder virus (CYSDV), a widely spread virus in Cyprus island, as well as with Cucurbit chlorotic yellows virus (CCYV), which is identified for the first time. Sequencing analysis showed 99% and 100% identities with the CCYV isolates from Greece and the Middle East. To our knowledge, this is the first report of CCYV infecting cucurbits in Cyprus and our findings support the notion that the virus is spreading in the Mediterranean basin and is an important pathogen in cucurbit crops. ( L.C. Papayiannis ) 46 Plant Protection