Search Results (5)

Tomato (Solanum lycopersicum L.), the second most important vegetable crop globally, faces a significant threat from various viral diseases. A newly emerging disease, characterised by distinctive shoestring symptoms on leaves and the development of unripe, small, and hard fruit, poses a serious challenge to tomato cultivation in India. An initial survey in an experimental field revealed more than 50% of the plants displayed symptoms of the shoestring disease, resulting in substantial reductions in fruit yield and quality. Transmission electron microscopy (TEM) and molecular analyses identified an isolate of the tomato mottle mosaic virus (ToMMV) in the affected plants. When the partially purified virus was mechanically inoculated into tomato cv. Pusa Ruby plants, it reproduced the characteristic shoestring symptoms, confirming its causal relationship with the disease. Notably, the present shoestring isolate of ToMMV (ToMMV-Tss) was found to induce similar shoestring symptoms in most of the major commercial tomato varieties when inoculated under controlled experimental conditions in the glasshouse, indicating its aggressive nature. Host range studies demonstrated that the ToMMV-Tss can infect several solanaceous species, while cucurbitaceous hosts remained unaffected. Moreover, the virus was found to be seed-transmissible, with a small percentage of seedlings from infected plants displaying symptoms. These findings underscore the significant impact of ToMMV on tomato production in India and emphasise the need for reliable diagnostic tools and effective management strategies to curb the spread and mitigate the impact of this virus on commercial tomato cultivation. Full article

Tomato mottle mosaic virus (ToMMV) is an emerging seed-transmissible tobamovirus that infects tomato and pepper. Since the first report in 2013 in Mexico, ToMMV has spread worldwide, posing a serious threat to the production of both crops. To prevent the spread of this virus, early and accurate detection of infection is required. In this study, we developed a detection method for ToMMV based on reverse-transcription loop-mediated isothermal amplification (RT-LAMP). A LAMP primer set was designed to target the genomic region spanning the movement protein and coat protein genes, which is a highly conserved sequence unique to ToMMV. This RT-LAMP detection method achieved 10-fold higher sensitivity than conventional RT-polymerase chain reaction methods and obtained high specificity without false positives for closely related tobamoviruses or healthy tomato plants. This method can detect ToMMV within 30 min of direct sampling of an infected tomato leaf using a toothpick and therefore does not require RNA purification. Given its high sensitivity, specificity, simplicity, and rapidity, the RT-LAMP method developed in this study is expected to be valuable for point-of-care testing in field surveys and for large-scale testing. Full article

Seed lots of tomato and capsicum (Solanum lycopersicon and Capsicum annuum, respectively) are required to be free of quarantine pests before their entry to Australia is permitted. Testing of samples from 118 larger seed lots in the period 2019–2021 revealed that 31 (26.3%) carried one or more of four Tobamovirus species, including tomato mottle mosaic virus (ToMMV), which is a quarantine pest for Australia. Testing of samples from a further 659 smaller seed lots showed that 123 (18.7%) carried a total of five Tobamovirus species, including ToMMV and tomato brown rugose fruit virus (ToBRFV), which is also a quarantine pest for Australia. Estimated prevalence of contamination by tobamoviruses ranged from 0.388% to 0.004% in contaminated larger seed lots. Analyses of these data allow us to estimate probabilities of detection of contamination under different regulatory settings. Full article

Tomato (Solanum lycopersicum) plants from a commercial glasshouse were identified with symptoms compatible with a tomato brown rugose fruit virus (ToBRFV) infection. Reverse transcription-PCR and quantitative PCR confirmed the presence of ToBRFV. Subsequently, the same RNA sample and a second from tomato plants infected with a similar tobamovirus, tomato mottle mosaic virus (ToMMV), were extracted and processed for high-throughput sequencing with the Oxford Nanopore Technology (ONT). For the targeted detection of ToBRFV, the two libraries were synthesized by using six ToBRFV sequence-specific primers in the reverse transcription step. This innovative target enrichment technology enabled deep coverage sequencing of ToBRFV, with 30% of the total reads mapping to the target virus genome and 57% mapping to the host genome. The same set of primers applied to the ToMMV library generated 5% of the total reads mapping to the latter virus, indicating that sequencing of similar, non-target viral sequences was also allowed. Further, the complete genome of pepino mosaic virus (PepMV) was also sequenced from the ToBRFV library, thus suggesting that, even using multiple sequence-specific primers, a low rate of off-target sequencing can usefully provide additional information on unexpected viral species coinfecting the same samples in an individual assay. These results demonstrate that targeted nanopore sequencing can specifically identify viral agents and has sufficient sensitivity towards non-target organisms to provide evidence of mixed virus infections. Full article

Tomato mottle mosaic virus (ToMMV) is a noteworthy virus which belongs to the Virgaviridae family and causes serious economic losses in tomato. Here, we isolated and cloned the full-length genome of a ToMMV Chinese isolate (ToMMV-LN) from a naturally infected tomato (Solanum lycopersicum L.). Sequence analysis showed that ToMMV-LN contains 6399 nucleotides (nts) and is most closely related to a ToMMV Mexican isolate with a sequence identity of 99.48%. Next, an infectious cDNA clone of ToMMV was constructed by a homologous recombination approach. Both the model host N. benthamiana and the natural hosts tomato and pepper developed severe symptoms upon agroinfiltration with pToMMV, which had a strong infectivity. Electron micrographs indicated that a large number of rigid rod-shaped ToMMV virions were observed from the agroinfiltrated N. benthamiana leaves. Finally, our results also confirmed that tomato plants inoculated with pToMMV led to a high infection rate of 100% in 4–5 weeks post-infiltration (wpi), while pepper plants inoculated with pToMMV led to an infection rate of 40–47% in 4–5 wpi. This is the first report of the development of a full-length infectious cDNA clone of ToMMV. We believe that this infectious clone will enable further studies of ToMMV genes function, pathogenicity and virus–host interaction. Full article