First report of cucurbit leaf crumple virus infecting three cucurbit crops in South Carolina

Authors: KEINATH, ANTHONY - Clemson University; Ling, Kai-Shu; Adkins, Scott; Hasegawa, Daniel; Simmons, Alvin; HOAK, STEVE - Glades Crop Care; MELLINGER, CHARLES - Glades Crop Care; Kousik, Chandrasekar - Shaker

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2018
Publication Date: 11/8/2018
Citation: Keinath, A.P., Ling, K., Adkins, S.T., Hasegawa, D.K., Simmons, A.M., Hoak, S., Mellinger, C., Kousik, C.S. 2018. First report of cucurbit leaf crumple virus infecting three cucurbit crops in South Carolina. Plant Health Progress. 19:322-323. https://doi.org/10.1094/PHP-07-18-0039-BR.
DOI: https://doi.org/10.1094/PHP-07-18-0039-BR

Interpretive Summary: Watermelon is an economically important vegetable crop growing throughout South Carolina. In 2017, watermelon growers in the coastal counties of South Carolina experienced a high number of whiteflies in their fall crop fields and observed a major disease outbreak with 50-100% of watermelon plants displaying leaf curl and crumple symptoms on leaves. Through molecular detection and sequence analysis by two independent ARS labs in Charleston and Ft. Pierce, the causal agent was determined to be Cucurbit leaf crumple virus (CuLCrV). This is the first report of CuLCrV) on watermelon. With the recent surge in whitefly population and all cucurbit crops are susceptible to CuLCrV, this whitefly-transmitted begomovirus will pose greater threat to all cucurbit crop productions in South Carolina and surrounding states.

Technical Abstract: Virus-like symptoms of curled and crumpled leaves accompanied by bright yellow chlorosis and marginal leaf necrosis typical of begomovirus infection were observed on watermelon (Citrullus lanatus) in Beaufort County in southeastern South Carolina in August 2017. Large populations of whiteflies (Bemisia tabaci) noted at this location prior to the appearance of symptoms also suggested a possible begomovirus infection. Four samples of watermelon leaves were collected from two adjoining farms, where 50-100% of plants displayed symptoms. Genus-specific primers for begomoviruses and potyviruses and species-specific primers for Cucurbit chlorotic yellows virus and Cucurbit yellow stunting disorder virus (CYSDV) were used in polymerase chain reactions (PCR) or reverse transcription-polymerase chain reaction (RT-PCR). Genus-specific primers for begomovirus-A component (PAR1c496 and PALv1978, Rojas et al. 1993) produced amplicons of the expected size (~1,100 bp) from each of the four samples. Additional genus-specific primers for begomovirus -B component (PBL1v2040 and PCR154, Rojas et al., 1993) confirmed the presence of a begomovirus in the samples. Sanger sequencing of amplicons from both A and B components and BLASTn analysis revealed a high nucleotide sequence identity of a representative watermelon sample with Cucurbit leaf crumple virus (CuLCrV). BLASTn analysis showed that 1,042 nt of the A component amplicon (GenBank accession no. MH013228) shared 97% nucleotide identity with both Arizona and California isolates of CuLCrV (AF256200 and AF224760, respectively). The 377-nt B component amplicon (GenBank accession no. MH013229) shared 94-95% nucleotide identity with the same Arizona and California CuLCrV isolates (AF327559 and AF224761, respectively). No amplicons were obtained with the other primers. Seven additional watermelon leaf samples collected from one of the farms in Beaufort County were tested by RT-PCR with primers specific for CuLCrV, CYSDV, Squash vein yellowing virus, or Papaya ringspot virus type W, common cucurbit viruses in the southeastern United States (Adkins et al. 2011). Total RNA was extracted from a pool of all seven samples using an RNeasy Plant Mini kit (Qiagen, Germantown, MD) followed by RT-PCR with previously described virus-specific primers and conditions (Turechek et al. 2010). The CuLCrV primers yielded an amplicon of 996 nt (GenBank accession no. MG920141) that shared 96-97% nucleotide identity with CuLCrV isolates in GenBank. No amplicons were obtained with SqVYV, CYSDV or PRSV-W primers. Transmission experiments using viruliferous B. tabaci on melon (Cucumis melo) seedlings resulted in leaf crumple symptoms on six test plants that resembled field symptoms. PCR with the primers PBL1v2040 and PCR154 produced amplicons of identical size from two test plants and the source materials. To our knowledge, this is the first report of CuLCrV infecting watermelon in South Carolina. Because CuLCrV is known to reduce watermelon yields, management of the whitefly vector in fall watermelon crops in South Carolina may be necessary in the future.