First report of barley virus G infecting wheat (Triticum aestivum) in Japan.

Abstract

Barley virus G (BVG) is a single stranded, positive sense RNA virus and tentative species of the genus Polerovirus in the family Solemoviridae. BVG was first identified in barley (Hordeum vulgare) in Korea with symptoms that were similar to those of barley yellow dwarf disease (Zhao et al. 2016). It has also been identified from proso millet (Park et al. 2017), barley (Erickson and Falk, 2021; Nancarrow et al. 2019; Svanella-Dumas et al. 2022), maize (Gavrili et al. 2021), wheat (Nancarrow et al. 2019), and oats (Nancarrow et al. 2019) in various countries. In the spring of 2019, wheat (Triticum aestivum) plants that exhibited symptoms of yellow leaves, necrosis, and stunting were observed in a few fields of the Chugoku region (western main island) in Japan. The four soil-borne viruses, wheat yellow mosaic virus (WYMV), Chinese yellow mosaic virus (CWMV), Japanese soil-borne wheat mosaic virus (JSBWMV), and soil-borne wheat mosaic virus (SBWMV), that often occur in winter wheat in Japan, were not detected by DAS-ELISA for WYMV, CWMV, and JSBWMV (Netsu et al. 2011) and ELISA Reagent Set for SBWMV (Agdia, IN, USA). To identify the pathogen, total RNA was isolated from the leaves and petioles using the PureLink RNA Mini kit (Thermo Fisher Scientific, MA, USA), and RT-PCR was performed using the PrimeScript One Step RT-PCR Kit Ver.2 (Dye plus) (Takara Bio Inc, Shiga, Japan). Based on the symptoms, luteoviruses and poleroviruses, which are transmitted by aphids, were suspected and RT-PCR was performed using known primers (Malmstrom and Shu, 2004; Mustafayev et al. 2013). This resulted in an amplicon of approximately 300 bp being obtained from RT-PCR using the Luteo2F/YanR-new primers (Mustafayev et al. 2013). The amplicon was directly sequenced by Sanger sequencing and a nucleotide BLAST search of the database revealed that the sequence was highly similar (99% identity, query coverage 95%) to the genome of BVG. In samples of a single field, four out of six plants that were showing necrosis and stunting were positive by RT-PCR using the primers BVG-CP-F (5´- GCGGGAAACATTTGTATTTTCG-3´)/BVG-CP-R (5´- GATTTTGGGTTAGAACATCCATCG-3´). In addition, five out of six plants with some yellowing of the leaves in the same field were also positive. Other luteoviruses and poleroviruses were not detected by RT-PCR using known primers. The full-length genome sequence of the Chugoku isolate was amplified using the primers BVG-F (5´-ACAAAAGGGACCCAGAGGG-3´)/BVG-R (5´-TACCAAGGATACTAGAGAGAGA-3´), which were designed from the 5´ and 3´ end sequences of the known BVG sequence. The resultant amplicon was directly sequenced by Sanger sequencing and the sequence was deposited into the DNA Data Bank of Japan (Chugoku isolate, LC649801). The sequence comprised of 5,620 bp and the genomic structures were consistent with that of BVG. The sequence showed more than 97% nucleotide identity with the BVG Gimji (KT962089), Uiseong (LC259081), NL1 (MF960779), and California (LC259081) isolates by pairwise comparisons. This is the first report of BVG in wheat in Japan to the best of our knowledge. The correlation between BVG and the observed symptoms and the impact of BVG on wheat production in Japan requires further investigation. Reference Erickson, A. C. and Falk, B. 2021. Plant Dis. doi:10.1094/PDIS-03-21-0478-PDN Gavrili, V. et al. 2021. J. Plant Pathol. 103:1331. doi:10.1007/s42161-021-00903-4 Malmstrom, C. M. and Shu, R. 2004. J. Virol. Methods. 120:69. doi:10.1016/j.jviromet.2004.04.005 Mustafayev, E. S. et al. 2013. Plant Dis. 97:849. doi:10.1094/PDIS-07-12-0656-PDN Nancarrow, N. et al. 2019. Plant Dis. 103:1799. doi: 10.1094/PDIS-01-19-0166-PDN Netsu, O. et al. 2011. Plant Dis. 58:13. doi.org/10.11337/ktpps.2011.13 Park, C.Y. et al. 2017. Plant Dis. 101:393. doi: 10.1094/PDIS-07-16-0952-PDN Svanella-Dumas, L. et al. 2022. Plant Dis. doi: 10.1094/PDIS-06-22-1294-PDN Zhao, F. et al. 2016. Arch. Virol. 161: 2047. doi:10.1007/s00705-016-2881-0.