Location: Crop Improvement and Protection ResearchTitle: Cucurbit chlorotic yellows virus, a new crinivirus infecting cucurbits in California
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/11/2018
Publication Date: 11/12/2018
Citation: Wintermantel, W.M., Hladky, L.L., Fashing, P.L., Ando, K., McCreight, J.D. 2018. Cucurbit chlorotic yellows virus, a new crinivirus infecting cucurbits in California. Cucurbitaceae 2018, November 12-15, 2018, Davis, California.
Technical Abstract: During the summer of 2018, melon (Cucumis melo L.) plants from a germplasm diversity study in Imperial Valley, California were found infected with Cucurbit chlorotic yellows virus (CCYV; genus Crinivirus, family Closteroviridae). Nearly all melon accessions in the study exhibited interveinal yellowing and chlorotic spot symptoms similar to those caused by Cucurbit yellow stunting disorder virus (CYSDV; genus Crinivirus), which has been prevalent in the region since 2006. However, nucleic acid extracts of two strongly symptomatic plants tested negative for CYSDV by RT-PCR. Subsequent RT-PCR evaluation of extracts of these two plants with primers specific for RNA-dependent RNA polymerase (RdRp) and coat protein (CP) gene sequences from CCYV RNA1 and RNA2, respectively, resulted in amplification. The 753 nt full-length CP gene and 1515 nt full-length RdRp gene of these isolates were sequenced, and each shared 99% sequence identity with the same regions of CCYV isolates from China, Greece, and Taiwan. Archived RNA extracts from Imperial Valley melon plants stored at -80C, and collected over the course of 9 years (2010-2018), were assayed for CCYV and CYSDV in order to determine how long CCYV may have been present in the region. Nineteen of 23 samples collected from 2014 to 2018 tested positive for CCYV, and many contained mixed infections of CCYV with CYSDV and/or the ipomovirus, Squash vein yellowing virus (SqVYV). Eighteen archived samples collected from 2010 to 2013 tested negative for CCYV, but CYSDV, the virus originally identified in the samples was successfully amplified from these archived extracts. Therefore, CCYV most likely emerged in the Imperial Valley in 2014, about the same time that SqVYV was first observed in California, but remained undetected due to similarity in symptomology on cucurbits to CYSDV. CCYV is transmitted efficiently by the whitefly, Bemisia tabaci MEAM1, which is common throughout the region. Preliminary observations suggest CYSDV resistance may not be effective for control of CCYV. Further studies will be necessary to evaluate epidemiology of CCYV in the southwestern U.S. desert crop production region, and to determine its impact on melon production and development of crinivirus-resistant melon cultivars.