Criniviruses associated with cucurbit yellows disease in Greece and Cyprus: an ever‐changing scene

Abstract

Cucurbit yellow stunting disorder virus (CYSDV), Cucurbit chlorotic yellows virus (CCYV) and Beet pseudo‐yellows virus (BPYV) are whitefly‐transmitted criniviruses that cause foliar interveinal yellowing symptoms and result in high economic losses for cucurbit production. CYSDV and CCYV are transmitted by Bemisia tabaci, whereas BPYV is transmitted by Trialeurodes vaporariorum. During 2012–2017, an extensive survey was conducted to identify the viruses causing cucurbit yellows disease in Greece and Cyprus. The study sampled the main cucurbits and alternative hosts in these regions to determine crinivirus incidence, to identify the whitefly species present in the two countries and to characterize molecularly the virus populations. Results showed that CYSDV was the most widespread virus in Greece (49.9%), followed by CCYV (20.3%) and BPYV (18.4%). Bemisia tabaci and T. vaporariorum were identified in 54.5% and 45.6% of whitefly samples, respectively. In Cyprus, CYSDV was predominant (96.7%), followed by CCYV (19.2%), while no BPYV infection was detected. Approximately 15% of weed samples from 17 different species that belong to 12 botanical families were identified as hosts for one or more of these criniviruses. Finally, sequencing of the capsid protein gene of the crinivirus isolates revealed very low levels of genetic diversity, further supporting the genetic stability of crinivirus populations. The results of this long‐lasting epidemiological study in two countries of the eastern Mediterranean revealed substantial changes in the relative incidence and distribution of cucurbit‐infecting criniviruses and their whitefly vectors over the past 15 years, suggesting the need for adoption of novel management strategies.