First Report of Beet Western Yellows Virus Infecting Wheat in Uzbekistan

Uzbekistan produces more than one million hectares of wheat (Triticum aestivum L.) annually, which is an important staple crop (Poaceae) consumed throughout the world. During April 2024 wheat plants in spring-planted fields in the Yukori Chirchiq and Qibray districts of Tashkent region of Uzbekistan, exhibited chlorotic spots at leaf tips and stunted growth, reminiscent of a virus-like disease. The incidence ranged from 25-30% and aphids were observed colonizing wheat plants in symptomatic fields in both districts. Aphids (alate and apterous) were collected and submitted for identification to the Entomology Laboratory Institute of Zoology, Academy of Sciences, Republic of Uzbekistan. Leaves of symptomatic (n = 5) and apparently symptom-free (n = 5) were collected from aphid-infested plants at the boot stage using a random sampling approach from a 50 × 50 m2 quadrant plot in three wheat fields. Total RNA was isolated and purified from wheat leaves, followed by cDNA synthesis. PCR was carried out on cDNA using the universal polerovirus primers, PococpR-3’-CGTCTACCTATTTSGGRTTN-5’ and PoconF- 3’-TGYTCYGGTTTTGACTGG-5’ (Xiang et al., 2008) to amplify a suspect polerovirus fragment encoding the partial RNA-dependent RNA polymerase, coat protein, and putative movement protein genes of ~1400 base pairs (bp) in size. A PCR amplicon of ~1400 bp in size was molecularly cloned and subjected to whole plasmid sequencing. To exclude mixed infection all samples tested negative for BYDV and BWYV in RT-PCR. A BLASTn analysis was carried out to identify the best matches yielding the highest sequence coverage among sequences available in the GenBank database. The sequence shared the highest similarity at 97.80% with beet western yellows virus (BWYV) isolate R3a (LC428357) from Raphanus sativus plants in Japan. The sequence was deposited in GenBank and assigned accession no. PV298533. The aphids collected from wheat plants were identified as Myzus persicae (Sulzer) based on established morphological characters (Blackman and Eastop 2000), a known vector of BWYV (Seddas et al. 2004). The results confirm that a BWYV-like polerovirus is associated with symptomatic, aphid-infested wheat plants, and represents the first report of BWYV in wheat plants in Central Asia (Uzbekistan), and only the second report of BWYV infecting wheat following that from China (Jin et al. 2023). Thus, BWYV and potentially other poleroviruses are emerging in grain crops because of increasing early-season infestations of the cereal aphid in Central Asia wheat crops, aggravated by extended periods of mild winter temperatures. These results suggest the impending emergence of poleroviruses as new threats to wheat production.

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