EPPO Alert List – Watermelon crinkle leaf-associated virus 1 (WCLaV-1) and WCLaV-2
Why
Watermelon crinkle leaf-associated virus 1 (Coguvirus, WCLaV-1) and Watermelon crinkle leaf-associated virus 2 (Coguvirus, WCLaV-2) are newly described viruses affecting watermelon and other cucurbits. Little is known about their biology, but considering their recent reports in different parts of the world and the potential damage that they may cause on cucurbits, the EPPO Secretariat decided to add WCLaV-1 and WCLaV-2 to the EPPO Alert List.
Where
WCLaV-1 and WCLaV-2 were first described in China in 2017.
WCLaV-1
Asia: China (Henan).
North America: USA (Florida, Georgia, Texas).
South America: Brazil (Bahia, Piaui, Rio Grande do Norte).
Oceania: Australia (New South Wales).
WCLaV-2
Asia: China (Henan).
North America: USA (Florida, Oklahoma, Texas).
South America: Brazil (Bahia, Rio Grande do Norte).
On which plants
WCLaV-1 and WCLaV-2 have been described causing damage on watermelon (Citrullus lanatus) and more recently on squash and zucchini (Cucurbita pepo). As little is known about these viruses, their host range may be wider.
Damage
Symptoms on leaves include mild leaf crinkling and yellow mosaic patterns, yellow mottling and chlorosis, and wrinkling with thickened, bunchy, and upward curling. Symptoms on fruit include circular lesions, and deformations. Symptoms may be severe and disease incidence up to 50% has been reported in commercial fields.
Transmission
More research is needed to assess the modes of transmission of these viruses. In experiments, WCLaV-1 and WCLaV-2 were shown to be transmissible mechanically. Both viruses may be found in mixed infections. No vectors have been identified so far but many viruses of the order Bunyavirales, to which Coguvirus belongs, are vectored by arthropods. The recent reports in different parts of the world suggest that WCLaV-1 and WCLaV-2 may be associated with seeds.
Pathways
Plants for planting. Seed? Fruits?
Possible risks
Watermelons and zucchini are widely grown in Southern Europe and around the Mediterranean Basin. WCLaV-1 and WCLaV-2 have been reported in different parts of the world and could probably also be introduced and establish into the EPPO region.
Sources
Hendricks KE, Hernandez RN, Roberts PD, Isakeit T, Alabi OJ (2022) First report of watermelon crinkle leaf-associated virus 1 (WCLaV-1) and WCLaV-2 in watermelon (Citrullus lanatus) plants coinfected with cucurbit chlorotic yellows virus in Florida. Plant Disease 106(1), 339. https://doi.org/10.1094/PDIS-06-21-1141-PDN
Hernandez RN, Isakeit T, Al Rwahnih M, Villegas C, Alabi OJ (2021) First report of watermelon crinkle leaf-associated virus 1 (WCLaV-1) and WCLaV-2 infecting watermelon (Citrullus lanatus) in the United States. Plant Disease 105(7), 2025. https://doi.org/10.1094/PDIS-02-21-0249-PDN
Iriarte F, Jailani AA, Paret ML (2023) First report of Watermelon crinkle leaf‐associated virus 1 (WCLaV‐1) on Cucurbita pepo in the United States. New Disease Reports 47(2), e12167. https://doi.org/10.1002/ndr2.12167
Jailani AAK, Iriarte FB, Paret ML (2023) First report of watermelon crinkle leaf-associated virus (WCLaV) -1 and WCLaV-2 infecting straightneck squash in the United States. Plant disease (early view). https://doi.org/10.1094/PDIS-01-23-0079-PDN
Maeda MH, Koyama LH, Campos RN, Kauffmann CM, Souza JO, Gilbertson R, Inoue-Nagata AK, Freitas DM, Nogueira DR, Melo FL, Nagata T (2022) First report of watermelon crinkle leaf-associated virus 1 and 2 infecting watermelon (Citrullus lanatus) plants in Brazil. Plant Disease 106(2), 773.
Mulholland S, Wildman O, Kinoti WM, Constable F, Daly A, Tesoriero L, Maina S, Chapman TA (2023) First report of watermelon crinkle leaf associated virus-1 (WCLaV-1) in watermelon (Citrullus lanatus) in Australia. Journal of Plant Pathology 105(1), 295-297. https://doi.org/10.1007/s42161-022-01250-8
Xin M, Cao M, Liu W, Ren Y, Zhou X, Wang X (2017) Two negative-strand RNA viruses identified in watermelon represent a novel clade in the order Bunyavirales. Frontiers in microbiology 8, 1514. https://doi.org/10.3389/fmicb.2017.01514
Zhang S, Tian X, Navarro B, Di Serio F, Cao M (2021) Watermelon crinkle leaf-associated virus 1 and watermelon crinkle leaf-associated virus 2 have a bipartite genome with molecular signatures typical of the members of the genus Coguvirus (family Phenuiviridae). Archives of Virology 166, 2829-2834.
EPPO RS 2013/116