First report of tomato bushy stunt virus naturally infecting sugar beet in the United States

Authors: Ramachandran, Vanitharani; Wyatt, Nathan; Rivera Santiago, Eric; Barth, Hunter; BLOOMQUIST, MARK - Southern Minnesota Beet Sugar Cooperative; WEILAND, JOHN - Beet Sugar Development Foundation; Bolton, Melvin

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2022
Publication Date: 6/10/2023
Citation: Ramachandran, V., Wyatt, N.A., Rivera Santiago, E.E., Barth, H.P., Bloomquist, M., Weiland, J., Bolton, M.D. 2023. First report of tomato bushy stunt virus naturally infecting sugar beet in the United States. Plant Disease. 107(6):1957. https://doi.org/10.1094/PDIS-11-22-2530-PDN.
DOI: https://doi.org/10.1094/PDIS-11-22-2530-PDN

Interpretive Summary: Sugar beet is an economically important source of sucrose that contributes to sugar industries globally. Sugar beet productivity is affected by viral diseases. In the United States, the Imperial Valley of California is a sugar beet production region known for viral disease issues. In March 2021, sugar beet plants showing stunted and bushy growth with leaf yellowing and necrosis suspicious of Tomato bushy stunt virus (TBSV) were observed in a production field in the Imperial Valley. Underground roots of the symptomatic plants showed stunted and abnormal growth compared to roots from healthy plants. TBSV produces bushy and necrotic symptoms primarily in tomato and vegetable crops but has been shown to infect sugar beet in countries outside of the U.S. In this study, we identified the presence of TBSV in the symptomatic sugar beet roots using both serological and molecular methods. To our knowledge, this is the first report of TBSV naturally infecting sugar beet in the United States. Identification of TBSV in sugar beet indicates the need for monitoring the etiology of the virus in sugar beet production fields, which is important for developing disease management strategies.

Technical Abstract: Sugar beet (Beta vulgaris L.) is an important crop grown for its sucrose content around the world. In March 2021, sugarbeet plants showing stunted and bushy growth with yellowing and necrotic leaf symptoms were observed in a production field in the Imperial Valley of California. The roots of the symptomatic plants showed stunted and abnormal growth compared to roots from healthy plants. These symptoms prompted a screen for potential infection by Tomato bushy stunt virus (TBSV) and initial serological testing revealed a positive reaction for TBSV using a double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). The presence of TBSV was confirmed by amplifying a portion of TBSV using reverse-transcription (RT)-PCR. Sequencing of the RT-PCR product confirmed the presence of TBSV genome with 95.2% identity to the TBSV reference genome (GenBank AJ249740.1). To obtain the full-length sequence of TBSV, total RNA isolated from the root-tissue was subjected to high-throughput sequencing (HTS). A single contig of 4770 nts representing the full-length genome of TBSV was generated, which showed 100% coverage and 92.17% sequence identity to a previously reported TBSV, “statice” isolate (AJ249740.1), thus confirming the presence of TBSV in sugar beet root tissue. Further, mechanical inoculation of total RNA isolated from the symptomatic sugar beet roots produced necrotic symptoms on the leaves of Chenopodium quinoa. Sequencing of the amplicon obtained using RT-PCR confirmed the presence of TBSV in C. quinoa. To our knowledge, this is the first report that documents the occurrence of TBSV in sugar beet in the United States. Since TBSV is a soil-borne virus, our findings indicate the need for further studies monitoring for etiology of the virus in sugar beet production fields, which will be essential for the development of disease management strategies.