First Report of Ranunculus white mottle ophiovirus in Slovenia in Pepper with yellow leaf curling symptom and in Tomato

Abstract

Pepper (Capsicum annuum) and Tomato (Solanum lycopersicum) plants showing virus-like disease symptoms were collected in 2017, 2019, and 2020, in different parts of Slovenia (Supplementary Figure 1). Total RNA was extracted from leaf tissue of individual samples using RNeasy Plant Mini kit (Qiagen) and pooled in four composite samples as follows: 2 pepper plants from 2017 (D2017), 5 pepper and 4 tomato plants from 2019 (D2019_P1), 7 tomato plants (D2020_P1), and 2 pepper and 4 tomato plants (D2020_P3) from 2020. The pooled RNA samples were sequenced using Illumina platforms, details of the sequencing experiments are in Supplementary Table 1. Reads were analyzed using CLC Genomics Workbench (v. 20.0, Qiagen) following the pipelines for plant virus discovery (Pecman et al., 2017). Reads and contigs mapping to Ranunculus white mottle ophiovirus (RWMV, GenBank accession no. AY542957 or NC_043389) were detected in all pools. The longest contig (1,255 bp) was obtained from the 2019 composite sample, mapping to the coat protein-coding RNA 3 segment of the RWMV genome (accession no. AY542957). Details of mapping, genome coverage, and other viruses detected in the pools are summarized in the Supplementary Table 1. To identify individual RWMV-infected plants from the pools, primers were designed for detection by reverse transcription-polymerase chain reaction (RT-PCR) targeting the coat protein gene (see Supplementary Table 2). Two pepper samples from two different farms, collected in 2017 and 2019 in southwest Slovenia, and four tomato samples from two different farms, collected in 2020 in central Slovenia tested positive for RWMV in RT-PCR assays. To assess the diversity of RWMV isolates, amplicons were purified using QIAquick PCR purification kit (Qiagen) and sent for Sanger sequencing. Based on maximum likelihood phylogenetic analysis, RWMV Italian and Slovenian isolates form a monophyletic clade within the genus (see Supplementary Figure 2). Pairwise nucleotide identities of the Slovenian isolates (accession no. MZ507604-MZ507609), relative to the original Italian isolate coat protein (accession no. AY542957) range from 92-97%, indicating a moderate level of diversity among isolates (see Supplementary Figure 2). Since only RWMV, bell pepper alphaendornavirus (BPEV), and pepper cryptic virus 2 (PepCV2), were present in a pepper sample from 2017, and BPEV and PepCV2 infection in pepper are not known to be associated with any of the disease symptoms (Okada et al., 2011; Saritha et al., 2016), the symptoms observed on this plant might be associated with RWMV infection. We observed mottling with interveinal chlorosis or yellowing, slight to full curling of leaves from lamina inward, as well as necrotic and aborted flowers on this plant (see Supplementary Figure 1). We cannot easily associate observed symptoms with RWMV in RWMV-positive tomatoes, since several viruses were detected in the pools containing these samples. Nevertheless, the prominent symptoms in tomato were mottling with interveinal chlorosis and leaf curling, similar to those observed in pepper. RWMV was discovered and characterized in buttercup (Ranunculus asiaticus), and detected in anemone (Anemone coronaria), from Italy (Vaira et al., 1996, 1997, 2000, 2003). It was recently detected in pepper from Australia showing veinal yellowing (Gambley et al., 2019). Here, we detected RWMV for the first time in Slovenia, and reported its first detection in tomato and pepper from Europe. These findings call for further studies on the effects of RWMV infection on tomato and pepper production, and its monitoring in neighboring European countries. Acknowledgment This study received funding from the Administration of the Republic of Slovenia for Food Safety, Veterinary Sector and Plant Protection, Slovenian Research Agency (ARRS) core financing (P4-0165), and the Horizon 2020 Marie Skłodowska-Curie Actions Innovative Training Network (H2020 MSCA-ITN) project “INEXTVIR” (GA 813542), under the management of the European Commission-Research Executive Agency. References Gambley, C., et al. 2019. New Dis. Rep. 40:13. doi:10.5197/j.2044-0588.2019.040.013. Okada, R., et al. 2011. J. Gen. Virol. 92:2664-2673. doi:10.1099/vir.0.034686-0. Pecman, A., et al. 2017. Front. Microbiol. 8:1-10. doi:10.3389/fmicb.2017.01998. Saritha, R. K., et al. 2016. VirusDisease 27:327-328. doi:10.1007/s13337-016-0327-7. Vaira, A. M., et al. 2003. Arch. Virol. 148:1037-1050. doi:10.1007/s00705-003-0016-x. Vaira, A. M., et al. 1996. Acta Hortic., 432:36-43. doi:10.17660/ActaHortic.1996.432.3. Vaira, A. M., et al. 1997. Arch. Virol. 142:2131-2146. doi:10.1007/s007050050231. Vaira, A. M., et al. 2000. Plant Dis. 84:1046-1046. doi:10.1094/PDIS.2000.84.9.1046B.