Since its first occurrence in Israel and Jordan in 2014 and 2015, the tomato brown rugose fruit virus (ToBRFV) has become one of the most concerning pathogens affecting tomatoes and other crops worldwide. Its rapid sp...
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Since its first occurrence in Israel and Jordan in 2014 and 2015, the tomato brown rugose fruit virus (ToBRFV) has become one of the most concerning pathogens affecting tomatoes and other crops worldwide. Its rapid spread is believed to result from the international trade of contaminated seeds and its seed transmissibility, underscoring the critical importance of seed health testing for ToBRFV to prevent further dissemination of the virus. To this end, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) protocols employing TaqMan probe chemistry have been widely adopted. However, the development of RT-qPCR protocols for ToBRFV seed testing using SYBR Green chemistry remains limited. The SYBR Green method offers the advantage of distinguishing ToBRFV from other tobamoviruses through melt curve analysis. In this study, we developed a SYBR Green-based RT-qPCR detection method using newly designed primer sets, which demonstrated high specificity for ToBRFV and sufficient sensitivity. While this protocol requires further optimization and validation for application in routine seed testing, it establishes a foundational approach for SYBR Green-based RT-qPCR seed testing. Additionally, this study raises an important question regarding the relationship between RT-qPCR results in seed tests and the likelihood of virus contamination or transmission via seeds.
Since the first report of the tobamovirus tomato brown rugose fruit virus (ToBRFV) in 2014, it has become globally distributed. Its rapid spread has been primarily attributed to seed-borne transmission. Here, the seed...
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Since the first report of the tobamovirus tomato brown rugose fruit virus (ToBRFV) in 2014, it has become globally distributed. Its rapid spread has been primarily attributed to seed-borne transmission. Here, the seed-borne nature of ToBRFV transmission was investigated in different cultivars of tomato, bell pepper, and eggplant. In situ hybridization to localize the virus in reproductive organs of ToBRFV-infected tomato plants revealed that the virus was not present in shoot apices, flower buds, or in ovules during flower opening, indicating the virus may be restricted to the outer integument and transported in the vascular bundles during seed development. However, during early fruit development, the virus was present in the integuments in the ovule. Seeds of tomato cultivars with or without tobamovirus resistance gene Tm-22 transmitted the virus to the progeny seedlings at rates that reflected the ineffectiveness of the gene against ToBRFV. Seeds of bell peppers transmitted ToBRFV at higher rates than tomato seeds, but a bell pepper cultivar that has resistance gene L3 was not systemically infected, and its seeds did not harbor the virus. Three eggplant cultivars were systemically infected with ToBRFV but without showing any obvious symptoms, and even though ToBRFV was present in their seeds, the seedlings were not infected. ToBRFV was detected in the seed coats of contaminated tomato and bell pepper seeds, but not in eggplant seed coats. These results indicate mechanistic differences in seed-borne transmission among the three Solanaceae crops.
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