Wheat (Triticum aestivum L.) is an important cereal crop widely cultivated worldwide. Viral disease is a major threat to wheat yield. In April 2022, fifteen winter wheat plants with yellowing and stunting symptoms were collected from wheat fields in Jingjiang, Jiangsu Province. Total RNA of each sample was extracted, and RT-PCR was performed using two pairs of degenerate luteovirus primers Lu-F (5'-CCAGTGGTTRTGGTC-3') and Lu-R (5'-GTCTACCTATTTGG-3'), Leu-F (5'-GCTCTAGAATTGTTAATGARTACGGTCG-3') and Leu-R (5'-CACGCGTCN ACCTATTTNGGRTTNTG-3'). Amplicons with the expected size were obtained from 10 of the 15 samples (using primers Lu-F/Lu-R) and 3 of the 15 samples (using primers Leu-F/Leu-R), respectively. These amplicons were cloned into the pDM18-T vector (TaKaRa) for sequencing. Blastn alignment showed that 10 amplicons (531 bp) from Lu-F/Lu-R primers were essentially identical to one another, which shared 99.62% nucleotide sequence identity to barley yellow dwarf virus-PAV (BYDV-PAV) isolate GJ1 from Avena sativa in South Korea (LC550014). Three amplicons (635 bp) from Leu-F/Leu-R primers had 99.68% nucleotide identity to the corresponding part of an isolate of beet western yellows virus (BWYV) from saffron (Crocus sativus) in China (MG002646). Among the 13 virus-positive samples, none were co-infected by BYDV-PAV and BWYV. Then, amplification using BWYV-specific primers (BWYV-F: 5'-TGCTCCGGTTTTGACTGGAGTGT-3', BWYV-R: 5'-CGTCTACCT ATTTTGGGTTGTGG-3') generated a 1409 bp product, corresponding to the partial sequence of the viral RNA-dependent RNA polymerase gene and complete sequence of the coat protein (CP) gene. The sequences (GenBank accession no. ON924175) of amplicons from 3 BWYV samples were identical to one another, which shared 98.41% nucleotide identity to BWYV isolate Hs from Japanese hop (Humulus scandens) in China (KC210049). The predicted coat protein of the BWYV wheat isolate had 99.51% nucleotide and 100% amino acid identity to BWYV isolate Hs. BWYV infection on wheat samples was also verified by dot-nucleic acid hybridization using a digoxigenin-labeled cDNA probe against the CP gene, as described previously (Liu et al. 2007). Further, RNA-positive samples were tested by enzyme-linked immunosorbent assay (ELISA) using the ELISA reagent kit for BWYV (Catalog No. KS19341, Shanghai Keshun Biotech, Shanghai, China); test results were also BWYV-positive, confirming that both BWYV nucleic and coat protein are present in these wheat samples. BYDV-PAV is a common wheat virus (Chay et al. 1996), while BWYV has never been reported to infect wheat. BWYV, an aphid-transmitted virus belonging to the Polerovirus genus, has an extensive host range, including over 150 plant species from 23 dicotyledonous families, such as Beta vulgaris, Spinacia oleracea, Lactuca sativa, and Brassica oleracea var. italica (Duffus 1964, 1973; Russell 1965; Beuve et al. 2008). In addition, BWYV was reported to infect a monocotyledonous plant, Crocus sativus (Iridaceae) (Zheng et al. 2018). To our knowledge, this is the first report of BWYV in wheat or any other Gramineae crop. The result also implies that BWYV has a potential risk to cereal crops in the field.
Keywords: Pathogen detection; Subject Areas; beet western yellows virus; viruses; wheat.