The tobamovirus tomato brown rugose fruit virus (ToBRFV) infects tomato plants harboring the Tm-22 resistance allele, which corresponds with tobamoviruses’ avirulence (Avr) gene encoding the movement ...protein to activate a resistance-associated hypersensitive response (HR). ToBRFV has caused severe damage to tomato crops worldwide. Unlike tomato plants, pepper plants harboring the L resistance alleles, which correspond with the tobamovirus Avr gene encoding the coat protein, have shown HR manifestations upon ToBRFV infection. We have found that ToBRFV inoculation of a wide range of undefined pepper plant varieties could cause a “hypersensitive-like cell death” response, which was associated with ToBRFV transient systemic infection dissociated from disease symptom manifestations on fruits. Susceptibility of pepper plants harboring L1, L3, or L4 resistance alleles to ToBRFV infection following HRs was similarly transient and dissociated from disease symptom manifestations on fruits. Interestingly, ToBRFV stable infection of a pepper cultivar not harboring the L gene was also not associated with disease symptoms on fruits, although ToBRFV was localized in the seed epidermis, parenchyma, and endothelium, which borders the endosperm, indicating that a stable infection of maternal origin of these tissues occurred. Pepper plants with systemic ToBRFV infection could constitute an inoculum source for adjacently grown tomato plants.
Tomato brown rugose fruit virus
(ToBRFV), belonging to the genus
Tobamovirus
, is a highly-virulent emerging virus species, causing disease outbreaks and significant crop losses worldwide. No ...effective measure has been identified to control ToBRFV infection. Therefore, the objectives of this study were to investigate the effectiveness of three seed disinfection treatments on the elimination of ToBRFV in tomato seeds and their effect on seed quality. Seeds extracted from ToBRFV-infected fruits were treated with 2% hydrochloric acid (HCl) for 30 min, 10% trisodium phosphate (TSP) for 3 h, dry heat at 72 °C for 72 h, or their combinations; then, the seeds were tested for the presence of the virus using serological, molecular, and biological assays. Parallel treatments of seeds in distilled water (hydropriming) or untreated seeds were included for comparison. The quality of the treated seeds was also evaluated in terms of seed standard germination, mean time to germination (MTG), and seedling growth. Seeds extracted from ToBRFV-infected fruits had a 100% contamination rate. Treatment of ToBRFV-contaminated seeds with 2% HCl for 30 min or 10% TSP for 3 h resulted in a 100% disinfection rate, while heat treatment at 72 °C for 72 h or hydropriming treatments resulted in a 0% disinfection rate. Furthermore, seed treatment with HCl or hydropriming for 3 h significantly improved seed germination percentage, reduced MTG (faster speed of germination), and increased seedling length. In conclusion, seed treatment with 2% HCl for 30 min not only resulted in a 100% disinfection rate of seeds from the ToBRFV but also improved seed quality of tomato compared to untreated seeds.
During tobamovirus–host coevolution, tobamoviruses developed numerous interactions with host susceptibility factors and exploited these interactions for replication and movement. The plant‐encoded ...TOBAMOVIRUS MULTIPLICATION (TOM) susceptibility proteins interact with the tobamovirus replicase proteins and allow the formation of the viral replication complex. Here CRISPR/Cas9‐mediated mutagenesis allowed the exploration of the roles of SlTOM1a, SlTOM1b, and SlTOM3 in systemic tobamovirus infection of tomato. Knockouts of both SlTOM1a and SlTOM3 in sltom1a/sltom3 plants resulted in an asymptomatic response to the infection with recently emerged tomato brown rugose fruit virus (ToBRFV). In addition, an accumulation of ToBRFV RNA and coat protein (CP) in sltom1a/sltom3 mutant plants was 516‐ and 25‐fold lower, respectively, than in wild‐type (WT) plants at 12 days postinoculation. In marked contrast, sltom1a/sltom3 plants were susceptible to previously known tomato viruses, tobacco mosaic virus (TMV) and tomato mosaic virus (ToMV), indicating that SlTOM1a and SlTOM3 are not essential for systemic infection of TMV and ToMV in tomato plants. Knockout of SlTOM1b alone did not contribute to ToBRFV and ToMV resistance. However, in triple mutants sltom1a/sltom3/sltom1b, ToMV accumulation was three‐fold lower than in WT plants, with no reduction in symptoms. These results indicate that SlTOM1a and SlTOM3 are essential for the replication of ToBRFV, but not for ToMV and TMV, which are associated with additional susceptibility proteins. Additionally, we showed that SlTOM1a and SlTOM3 positively regulate the tobamovirus susceptibility gene SlARL8a3. Moreover, we found that the SlTOM family is involved in the regulation of plant development.
Knockouts of both SlTOM1a and SlTOM3 resulted in an asymptomatic response to ToBRFV, but were susceptible to ToMV and TMV, and SlTOM1a and SlTOM3 positively regulate the tobamovirus susceptibility gene SlARL8a3.
Plant viruses of the genus
Tobamovirus
cause significant economic losses in various crops. The emergence of new tobamoviruses such as the tomato brown rugose fruit virus (ToBRFV) poses a major threat ...to global agriculture. Upon infection, plants mount a complex immune response to restrict virus replication and spread, involving a multilayered defense system that includes defense hormones, RNA silencing, and immune receptors. To counter these defenses, tobamoviruses have evolved various strategies to evade or suppress the different immune pathways. Understanding the interactions between tobamoviruses and the plant immune pathways is crucial for the development of effective control measures and genetic resistance to these viruses. In this review, we discuss past and current knowledge of the intricate relationship between tobamoviruses and host immunity. We use this knowledge to understand the emergence of ToBRFV and discuss potential approaches for the development of new resistance strategies to cope with emerging tobamoviruses.
Tobamoviruses, including tomato brown rugose fruit virus (ToBRFV) on tomato and pepper, and cucumber green mottle mosaic virus (CGMMV) on cucumber and watermelon, have caused many disease outbreaks ...around the world in recent years. With seed-borne, mechanical transmission and resistant breaking traits, tobamoviruses pose serious threat to vegetable production worldwide. With the absence of a commercial resistant cultivar, growers are encouraged to take preventative measures to manage those highly contagious viral diseases. However, there is no information available on which disinfectants are effective to deactivate the virus infectivity on contaminated hands, tools and equipment for these emerging tobamoviruses. The purpose of this study was to evaluate a collection of 16 chemical disinfectants for their effectiveness against mechanical transmission of two emerging tobamoviruses, ToBRFV and CGMMV.
Bioassay was used to evaluate the efficacy of each disinfectant based on virus infectivity remaining in a prepared virus inoculum after three short exposure times (10 s, 30 s and 60 s) to the disinfectant and inoculated mechanically on three respective test plants (ToBRFV on tomato and CGMMV on watermelon). Percent infection of plants was measured through symptom observation on the test plants and the presence of the virus was confirmed through an enzyme-linked immunosorbent assay with appropriate antibodies. Statistical analysis was performed using one-way ANOVA based on data collected from three independent experiments.
Through comparative analysis of percent infection of test plants, a similar trend of efficacy among 16 disinfectants was observed between the two pathosystems. Four common disinfectants with broad spectrum activities against two different tobamoviruses were identified. Those effective disinfectants with 90-100% efficacy against both tobamoviruses were 0.5% Lactoferrin, 2% Virocid, and 10% Clorox, plus 2% Virkon against CGMMV and 3% Virkon against ToBRFV. In addition, SP2700 generated a significant effect against CGMMV, but poorly against ToBRFV.
Identification of common disinfectants against ToBRFV and CGMMV, two emerging tobamoviruses in two different pathosystems suggest their potential broader effects against other tobamoviruses or even other viruses.
Tomato brown rugose fruit virus (ToBRFV) is a highly infectious virus, that is becoming a threat to tomato production worldwide. In this work we evaluated the localization of ToBRFV particles in ...tomato seeds, its seed transmission rate and efficacy of disinfection, and the effects of different thermal- and chemical-based treatments on ToBRFV-infected seeds’ germination. Analyses demonstrated that ToBRFV was located in the seed coat, sometime in the endosperm, but never in the embryo; its transmission from infected seeds to plantlets occurs by micro-lesions during the germination. The ToBRFV seed transmission rate was 2.8% in cotyledons and 1.8% in the third true leaf. Regarding the different disinfection treatments, they returned 100% of germination at 14 days post-treatment (dpt), except for the treatment with 2% hydrochloric acid +1.5% sodium hypochlorite for 24 h, for which no seed germinated after 14 dpt. All treatments have the ability to inactivate ToBRFV, but in six out of seven treatments ToBRFV was still detectable by RT-qPCR. These results raise many questions about the correct way to carry out diagnosis at customs. To our knowledge, this is the first study on the effective localization of ToBRFV particles in seeds.
The soil‐borne virus known as tomato brown rugose fruit virus (ToBRFV) has a low rate of around 3% soil‐mediated infection when the soil has root debris from a previous 30–50 day development cycle of ...tomato plants infected with ToBRFV. This study presents anti‐viral coating formulations based on Pickering emulsion. The coating formulation is based on water‐in‐canola oil emulsions stabilized using commercial hydrophobic silica, with water‐soluble polymer (sodium polyacrylic acid). The structure of the emulsions and their stability were characterized by confocal microscopy, centrifugal analysis using a LUMiSizer®, used to confirm the emulsion stability. We tested a few different silica concentration‐based formulations, which were prepared with or without the addition of various virus disinfectants. We found that under conditions of 100% soil‐mediated ToBRFV infection of uncoated positive control plants, root‐coating with formulations based on silica Pickering emulsion were prepared with the disinfectant chlorinated‐trisodium phosphate (TSP‐Cl) showed low percentages of soil‐mediated ToBRFV infection. These formulations had no adverse effect on plant growth parameters when compared to negative control plants grown under non ToBRFV inoculation conditions.
The reaction of 636
Solanum
(sections
Lycopersicon
and
Juglandifolia
) accessions were evaluated under greenhouse conditions after mechanical inoculation with a Jordanian isolate of the new ...tobamovirus tomato brown rugose fruit virus (ToBRFV). Local and systemic infections were assayed by symptoms evaluation and virus detection via biotests and RT-PCR. All cultivated tomatoes (
Solanum lycopersicum
) and the great majority of wild tomato accessions proved susceptible to ToBRFV. They showed a wide range of symptoms (mosaic, leaf deformations, mottling, shoestring, and stunting). Twenty-six accessions representing
S. lycopersicum
var. cerasiforme,
S. pimpinellifolium
,
S. habrochaites,
and
S. chilense
were tolerant. High levels of resistance have been demonstrated in three accessions of
S. ochrantum
, a close relative to wild tomatoes (member of the sect.
Juglandifolia
) not only to ToBRFV but also to the tobamoviruses, tobacco mosaic virus (TMV) and tomato mosaic virus (ToMV). After mechanical inoculation, the three tobamoviruses could be detected only in inoculated leaves in the accessions LA2160, LA2162, and LA 2166, which remained symptomless. However, two other
S. ochrantum
accessions PI 473,498 and PI 230,519 reacted unusually. They were demonstrated highly resistant to TMV and ToMV, but proved transiently susceptible to ToBRFV showing mild systemic mosaic followed by total recovery from symptoms and the virus.
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