Comparative analysis of host range, ability to infect tomato cultivars with Tm-2^2 gene and real-time RT-PCR detection of tomato brown rugose fruit virus

Authors: Chanda, Bidisha; Gilliard, Andrea; Jaiswal, Namrata; Ling, Kai-Shu

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2021
Publication Date: 6/7/2021
Citation: Chanda, B., Gilliard, A.C., Ling, K.S., Jaiswal, N. 2021. Comparative analysis of host range, ability to infect tomato cultivars with Tm-2^2 gene and real-time RT-PCR detection of tomato brown rugose fruit virus. Plant Disease. 105:3543-3352. https://doi.org/10.1094/PDIS-05-20-1070-RE.
DOI: https://doi.org/10.1094/PDIS-05-20-1070-RE

Interpretive Summary: Tomato (Solanum lycopersicum L.) is one of the most important vegetable crops, with the United States as the third largest producer in the world with 12.6 million ton annually. Tomato is especially susceptible to many viral diseases, which are difficult to manage. In the last few years, a new species of tobamovirus, tomato brown rugose fruit virus (ToBRFV), originally identified in the Middle East since 2014, has been identified to cause outbreaks in greenhouse tomatoes around the world, including the U.S. In this study, ARS scientists at the U.S. Vegetable Laboratory in Charleston, SC, conducted a comparative evaluation of potential host range among three major tobamoviruses. Although these tobamoviruses, including ToBRFV, tomato mosaic virus (ToMV) and tomato mottle mosaic virus (ToMMV), shared many similar host species, some unique species were also found for each specific virus in comparative analysis of disease resistance breaking to Tm-2^2 gene by the same three tobamoviruses. Disease resistant breaking to the Tm-2^2 gene was confirmed for ToBRFV, whereas those same cultivars with Tm-2^2 gene were resistant to ToMV and ToMMV. Finallly, we developed a species-specific real-time polymerase chain reaction technology useful for plant and seed health assays. The knowledge in biological properties and development of a sensitive detection tool for ToBRFV are critically important in bringing this emerging viral disease under control.

Technical Abstract: Tomato (Solanum lycopersicum L.) is one of the most important vegetables in the world. However, tomato is also susceptible to many viral diseases. Several tobamoviruses, including tomato mosaic virus (TMV), tomato mottle mosaic virus (ToMMV) and tomato brown rugose fruit virus (ToBRFV), are highly contagious pathogens, which could result in significant economic losses if not managed effectively. Tobamoviruses have been managed relatively well with broad adaptation of tomato cultivars with resistance genes. However, recent emergence of ToBRFV was shown to break the common resistance genes, resulting in serious outbreaks in many countries in Asia, Europe, and North America. The objective of this study was to conduct a comparative analysis of biological properties, including host range and disease resistance among ToMV, ToMMV and ToBRFV. Results showed that despite many similarities in host range, there were some unique host plant responses for each respective virus. In comparative evaluation of disease resistance using the same tomato cultivars with or without Tm-22 gene, there was a striking difference in responses from tomato plants with Tm-22 gene inoculated with ToBRFV, ToMV or ToMMV. Whereas these test plants were resistant to ToMV or ToMMV infection, all test plants were susceptible to ToBRFV. To develop a sensitive and reliable detection method for ToBRFV identification, a real-time reverse transcription polymerase chain reaction (RT-qPCR) was developed. With simple modifications to ribonucleic acid (RNA) extraction and seed soaking, RT-qPCR could detect consistently the virus in single infested seed in varied levels of contamination, suggesting its usefulness for seed health assay.