Search Results (85)

Tomato yellow leaf curl virus (TYLCV) is a highly destructive pathogen of global tomato crops. The open reading frame (ORF) of TYLCV V2 contains two initiation codons (ATG1/V2-1 and ATG2/V2-2), producing distinct protein isoforms. Using custom antibodies, we confirmed V2-1 and V2-2 expression in infected Nicotiana benthamiana and tomato plants. Deletion mutants revealed their specialized roles: V2-1 was indispensable for viral replication and systemic spread—its loss severely reduced pathogenicity and genome accumulation. V2-2 acted as an auxiliary factor, and its deletion attenuated symptoms but kept the virus infection. Host-specific effects were observed—V2-1 deletion led to lower viral DNA/coat protein levels in N. benthamiana than in tomato, suggesting host-dependent regulation. Mutant viruses declined progressively in tomato, indicating host defense clearance. Heterologous co-expression of both isoforms via potato virus X induced systemic necrosis in N. benthamiana, demonstrating functional synergy between isoforms. Both initiation codons were essential for V2-mediated suppression of transcriptional gene silencing (TGS) and post-transcriptional gene silencing (PTGS). This study uncovers the mechanistic divergence of V2 isoforms in TYLCV infection, highlighting their collaborative roles in virulence and host manipulation. The findings advance understanding of geminivirus coding complexity and offer potential targets for resistance strategies. Full article

Tomato (Solanum lycopersicum) is an essential vegetable crop cultivated worldwide, but its production is highly vulnerable to tomato yellow leaf curl disease (TYLCD), which is transmitted by whiteflies (Bemisia tabaci). Management strategies typically focus on controlling either the virus or its vector. This study evaluates the effectiveness of multi-disease and insect-resistant tomato lines, developed by the World Vegetable Center (WorldVeg), which integrate Ty-1/Ty-3 genes for virus resistance and WF2-10 and WF3-09 genes for whitefly resistance. Virus accumulation, whitefly settling behavior, and adult mortality were assessed among multi-resistant lines, a Ty-resistant line, a whitefly-resistant line, and a susceptible check using preference bioassays, controlled inoculation experiments, and acylsugar quantification. Multi-resistant lines exhibited significantly higher acylsugar concentrations, reduced whitefly preference for settling, and increased whitefly adult mortality. Additionally, these lines displayed less severe disease symptoms and lower virus accumulation over time than Ty-resistant, whitefly-resistant, and susceptible controls. These findings highlight the superior efficacy of combined virus and vector resistance in mitigating tomato yellow leaf curl Thailand virus (TYLCTHV) transmission. This research underscores the importance of integrated genetic resistance as a key element of sustainable integrated pest management strategies, offering an environmentally friendly solution for safeguarding global tomato production. Full article

Tomato yellow leaf curl disease poses one of the most severe threats to tomato production worldwide. This disease is associated with a group of closely related tomato yellow leaf curl viruses. These viruses can be transmitted by the sweet potato whitefly (Bemisia tabaci) in a persistent-circulative mode. Virus particles can infect the midgut and filter chamber of whiteflies feeding on infected plants, circulate in the hemolymph, and eventually infect the primary salivary gland (PSG) of whiteflies. Later, the whiteflies feed on healthy plants, and viral particles are introduced into the plants through their saliva. Virus–vector interactions play a crucial role in the efficiency and dynamics of virus transmission. In this study, we assessed the effects of the acquisition time and viral load of source plants on infections of two tomato begomoviruses, tomato yellow leaf curl Thailand virus (TYLCTHV) and tomato leaf curl Taiwan virus (ToLCTV), in B. tabaci Middle East–Asia Minor 1. We found that more viruses were acquired and accumulated in the whitefly midgut and PSG before reaching a plateau when the acquisition time increased and when the source plant had a higher viral load. The midgut and PSG acquired and accumulated more TYLCTHV than ToLCTV with the same acquisition time and regardless of the viral loads in coinfected source plants. These results not only help us to understand virus–vector interactions but also help in developing integrated disease management strategies. Full article

Tomato yellow leaf curl disease (TYLCD) significantly affects tomato yield. The jasmonic acid (JA) pathway is crucial in the defence response of plants; however, its role in plant resistance to TYLCD remains undefined. In production, CCC (chlorocholine chloride) is often used to cultivate strong seedlings to enhance seedling vitality and improve stress resistance. However, the mechanism through which CCC enhances disease resistance in tomatoes remains unclear. In this study, tomato seedlings were exogenously sprayed with 300 mg/L CCC before and after inoculation with tomato yellow leaf curl virus (TYLCV). The results indicated that no significant tomato yellow virus disease phenotype was observed in tomato seedlings after spraying with CCC and subsequent inoculation with the virus. Spraying CCC on seedlings inoculated with the virus and exhibiting typical phenotypes can significantly alleviate the yellowing and curling symptoms of new leaves and improve photosynthesis-related indicators in tomato plants. The detection of virus copy numbers within the plants revealed that the virus copy numbers in plants treated with CCC were significantly lower than those in the control group. Transcriptomic analysis revealed that, after spraying CCC, the key enzyme genes AOS2 and AOC in the JA synthesis pathway in tomatoes were significantly upregulated, whereas the expressions of JAZ2 and MYC2 genes, which negatively regulate JA synthesis, were significantly downregulated. In the stable state, JAZ proteins interact with MYC2 and inhibit its transcriptional activity of MYC2. Tomatoes overexpressing MYC2 and JAZ2 exhibit a significant decrease in TYLCD resistance. These results indicated that exogenous spraying CCC affected the expression of genes such as MYC2 and JAZ2, and then regulated JA pathway, increased the endogenous JA content in plants, and enhanced the disease resistance of tomato plants to TYLCD. This study provides a scientific reference for effectively preventing and controlling TYLCD in tomato production and reducing the influence of TYLCD on tomato yield and quality. Full article

Tomato yellow leaf curl virus (TYLCV), tomato leaf curl New Delhi virus (ToLCNDV), and tomato chlorosis virus (ToCV) are emerging viruses that cause significant damage to tomato (Solanum lycopersicum). TYLCV and ToLCNDV are single-stranded DNA viruses from the genus Begomovirus, family Geminiviridae, while ToCV is an RNA virus from the genus Crinivirus (family Closteroviridae). These viruses share overlapping geographic ranges, vectors (the whitefly Bemisia tabaci), and host plants, making mixed infections common. This study investigated interactions between TYLCV and ToLCNDV and between ToLCNDV and ToCV in mixed infections of susceptible and TYLCV-resistant tomato genotypes. We evaluated infection, disease development, trans-replication of genome components, and genetic exchange. Our results showed no significant synergistic or antagonistic interactions, complementation, or interference between the viruses. TYLCV resistance in tomato genotypes remained stable. The DNA-B component of ToLCNDV exhibited impaired functionality and was not complemented by TYLCV. No evidence was found that the crinivirus tomato chlorosis virus (ToCV) enhances ToLCNDV infection, suggesting limited interactions despite shared vectors. Genetic exchange was detected in defective DNA (def-DNA) molecules using high-throughput sequencing (HTS), indicating potential genetic interactions between these viruses. These findings suggest that mixed infections do not pose immediate concerns for increased pathogenicity but highlight the ecological implications of genetic exchange, warranting further study of the evolutionary consequences of such interactions in mixed-virus environments. Full article

Lettuce (Lactuca sativa L.) plants showing leaf curl and vein enation symptoms were found in Yunnan province, China. PCR detection with genus-specific primers revealed that symptomatic lettuce plants were infected with Begomovirus. The full-length viral component and satellite molecules were obtained by RCA, restriction enzyme digestion, PCR, cloning and DNA sequencing. A viral component (YN-2023-WJ) and three satellite molecules (YN-2023-WJ-alpha1, YN-2023-WJ-alpha2 and YN-2023-WJ-beta) were obtained from diseased lettuce plants. YN-2023-WJ exhibited the highest nt identity at 97.1% with pepper leaf curl Yunnan virus isolated from cigar plants. YN-2023-WJ-beta displayed the highest nt identity at 93.9% with tomato leaf curl China betasatellite. YN-2023-WJ-alpha1 showed the highest nt identity at 94.7% with ageratum yellow vein alphasatellite. YN-2023-WJ-alpha2 shared the highest nt identity at 75.6% with gossypium mustelinum symptomless alphasatellite and vernonia yellow vein Fujian alphasatellite. Based on the threshold for the classification of Begomovirus, Betasatellite and Alphasatellite, YN-2023-WJ was designated as a new isolate of PepLCYnV, YN-2023-WJ-beta as a new isolate of ToLCCNB and YN-2023-WJ-alpha1 as a new member of AYVA, whereas YN-2023-WJ-alpha2 was identified as a new geminialphasatellite species, for which the name pepper leaf curl Yunnan alphasatellite (PepLCYnA) is proposed. To the best of our knowledge, this is the first report of L. sativa L. infection by PepLCYnV associated with ToLCCNB, AYVA and PepLCYnA, and L. sativa L. is a new host plant of Begomovirus. Full article

Tomato leaf curl New Delhi virus (ToLCNDV) and tomato yellow leaf curl virus (TYLCV) are two important viral pathogens that severely affect Solanaceae and Cucurbitaceae plants. In order to reduce the further spread of these viruses, it is crucial to establish an efficient and reliable method to accurately detect the viruses. In this study, a multiplex PCR assay for the simultaneous detection of TYLCV and ToLCNDV was established. Three primer pairs designed from conserved regions within the coat protein or movement protein-encoding regions of the respective viruses were employed in the assay. The optimization of parameters such as primer concentration was set at 0.15 μM/0.15 μM, 0.25 μM/0.25 μM, and 0.50 μM/0.50 μM for ToLCNDV-DNA-A-F/R, TYLCV-F/R, and ToLCNDV-DNA-B-F/R primer pairs. At optimal primer concentrations, the multiplex PCR method demonstrates effective performance with an annealing temperature ranging from 51 °C to 66 °C. The specificity of the assay evaluated by testing against other begomoviruses showed no evidence of cross-amplification. Further sensitivity analysis performed using a serially diluted plasmid containing viral targets as templates demonstrated high sensitivity with a detection limit of 10³ copies/μL. Field surveys utilizing the multiplex PCR assay successfully identified the infection of TYLCV and ToLCNDV in field-collected samples. Full article

Among begomovirus species, tomato leaf curl New Delhi virus (ToLCNDV) is significant and stands out as a mechanically transmissible bipartite begomovirus originating from the Old World. However, the mechanisms underlying the mechanical transmission of different ToLCNDV strains remain understudied, as their natural transmission occurs via insect vectors. In this study, we investigated the mechanical transmissibility of two ToLCNDVs, one from Italy and another from Pakistan, in host plants. Several cucurbit species were screened, and symptom differences between the two ToLCNDV clones were observed only in zucchini when subjected to rubbing inoculation. The Italian isolate (ToLCNDV-ES) induced typical disease symptoms such as leaf curling, yellow mosaic, and internode stunting, whereas a normal phenotype was observed in zucchini mechanically infected with ToLCNDV-In (Pakistani isolate). Subsequently, a gene-swapping experiment between the two ToLCNDVs was conducted, and ToLCNDV-ES DNA-B was identified as a crucial factor in mechanical transmission. We then constructed chimeric mutant clones based on the DNA-B sequence and assessed their ability to induce symptoms in zucchini. These results indicated that the nuclear shuttle protein is a determinant of symptom development during ToLCNDV mechanical transmission. Moreover, several defense-related host genes showed significant changes in relative expression in different ToLCNDV clones, indicating their potential role in disease symptom development through the mechanical transmission of ToLCNDV. This is the first report comparing the mechanical transmissibility of two isolates of different ToLCNDV strains from the Mediterranean region and the Indian subcontinent in the same host plant, providing new insights into the virus’s pathogenicity across different geographic regions. Full article

Tomato yellow leaf curl virus (TYLCV) poses a significant threat to tomato production, leading to severe yield losses. The current control strategies primarily rely on the use of pesticides, which are often nonselective and costly. Therefore, there is an urgent need to identify more environmentally friendly alternatives. Dufulin, a novel compound that has been effective in controlling viral diseases in tobacco and rice, has not yet been tested against TYLCV. This study assessed the efficacy of dufulin in controlling TYLCV over a three-year span from 2021 to 2023 through field trials, by monitoring disease symptoms and viral titers. Additionally, this study assessed the expression levels of genes associated with systemic acquired resistance (SAR), specifically proteinase inhibitor II (PI II) and non-expressor of pathogenesis-related genes 1 (NPR1), using real-time qRT-PCR. The chlorophyll and nitrogen content in the leaves were also measured. Plants treated with dufulin showed reduced symptomatology and lower viral titers compared to the controls. Analysis of gene expression revealed that NPR1 was upregulated in the dufulin-treated plants, whereas PI II expression was consistently downregulated in the TYLCV-infected plants. Interestingly, PI II expression increased in the healthy plants following a seven-day post-treatment with dufulin. Moreover, the treated plants exhibited a higher chlorophyll content than the controls, though no significant differences in the nitrogen levels were observed between the dufulin-treated and water-treated plants. Overall, the application of dufulin significantly bolstered the plant’s defense response, effectively reducing TYLCV symptoms and enhancing resistance. Full article

Diseases caused by begomoviruses such as tomato yellow leaf curl disease (TYLCD) are major constraints in agriculture. While the interactions between plants and monopartite begomoviruses during TYLCD pathogenesis have been explored extensively, how bipartite begomoviruses interact with tomato plants are understudied. Here we first found that a bipartite begomovirus tomato yellow leaf curl Thailand virus (TYLCTHV) induced stunted growth, leaf curl and yellowing in tomato plants. We then profiled the tomato transcriptomic changes in response to TYLCTHV infection. In total, we identified 2322 upregulated and 1377 downregulated genes. KEGG enrichment analysis of the differentially expressed genes (DEGs) revealed that many KEGG pathways regulating plant photosynthesis processes and defenses were enriched. Specifically, TYLCTHV infection disrupted the expression of DEGs that function in the light-harvesting chlorophyll protein complex, photosystem I and II, cytochrome b6/f complex, photosynthetic electron transport and F-type ATPase. Additionally, the expression of many DEGs regulating plant defenses including pathogen-associated molecular pattern (PAMP)-triggered immunity, effector-triggered immunity and hypersensitive response was upregulated upon TYLCTHV infection. Taken together, we found that during the pathogenesis of TYLCD induced by TYLCTHV, the virus actively disrupts plant photosynthesis processes and induces defense responses. Our findings add to our knowledge of TYLCD pathogenesis and plant–virus interactions in general. Full article

Common bean (Phaseolus vulgaris L.) is a widely cultivated crop, representing an important protein source in the human diet in developing countries. The production of this crop faces serious challenges, such as virus diseases transmitted by the whitefly Bemisia tabaci. Although there is a lot of information about some of these viruses, most of what we know has been developed using model systems, such as tomato plants and tomato yellow leaf curl virus (TYLCV). There is still very little information on the most relevant common bean viruses, such as bean golden mosaic virus (BGMV), bean golden yellow mosaic virus (BGYMV), bean dwarf mosaic virus (BDMV), cowpea mild mottle virus (CPMMV), and bean yellow disorder virus (BnYDV). In this review, we discuss the available data in the most up-to-date literature and suggest future research avenues to contribute to the development of management tools for preventing or reducing the damage caused by viruses in this important crop. Full article

Tomato yellow leaf curl virus (TYLCV) causes significant yield loss in tomato production in the southeastern United States and elsewhere. TYLCV is transmitted by the whitefly Bemisia tabaci cryptic species in a persistent, circulative, and non-propagative manner. Unexpectedly, transovarial and sexual transmission of TYLCV has been reported for one strain from Israel. In this study, the potential contribution of the B. tabaci B cryptic species transovarial and sexual transmission of TYLCV (Israel strain, Georgia variant, Georgia, USA) to reoccurring outbreaks was investigated by conducting whitefly-TYLCV transmission assays and virus DNA detection using end point PCR, DNA quantitation via real-time PCR, and virion detection by immunocapture PCR. TYLCV DNA was detectable in four, two, and two percent of first-generation fourth-instar nymphs, first-generation adults, and second-generation adults, respectively, following transovarial acquisition. Post-mating between viruliferous counterparts, the virus’s DNA was detected in four percent of males and undetectable in females. The accumulation of TYLCV DNA in whiteflies from the transovarial and/or sexual experiments was substantially lower (100 to 1000-fold) compared with whitefly adults allowed a 48-hr acquisition-access period on plants infected with TYLCV. Despite the detection of TYLCV DNA in whiteflies from the transovarial and/or mating experiments, the virions were undetectable by immunocapture PCR—a technique specifically designed to detect virions. Furthermore, tomato test plants exposed to whitefly adults that presumably acquired TYLCV transovarially or through mating remained free of detectable TYLCV DNA. Collectively, the extremely low levels of TYLCV DNA and complete absence of virions detected in whiteflies and the inability of the B. tabaci cryptic species B to transmit TYLCV to test tomato plants following transovarial and mating acquisition indicate that neither transovarial nor sexual transmission of TYLCV are probable or epidemiologically relevant for TYLCV persistence in this pathosystem. Full article

Begomoviruses, transmitted by the whitefly Bemisia tabaci, pose significant threats to global agriculture due to their severe impact on various crops. Among the satellite molecules associated with begomoviruses, betasatellites play a crucial role in enhancing disease severity and yield losses. The spread and association of these molecules with helper viruses in host plants are thus matters of concern. Here, we focus on the propagation of betasatellites and, more specifically, on their transfer between different helper viruses and hosts through vector transmission. Our results show that the cotton leaf curl Gezira betasatellite (CLCuGeB), initially acquired with its helper virus cotton leaf curl Gezira virus (CLCuGeV) from an okra plant, can be transmitted and assisted by a different helper virus, tomato yellow leaf curl virus (TYLCV), in a different host plant (tomato plant). The new association can be formed whether TYLCV and CLCuGeB encounter each other in a host plant previously infected with TYLCV or in whiteflies having acquired the different components separately. Our findings reveal two pathways by which betasatellites can be transferred between helper viruses and host plants and highlight the ability of betasatellites to spread in begomovirus-infected environments. Full article

Tomato (Solanum lycopersicum L.) is a crop that is affected by more than a hundred viral species. De la pera is a local varietal type of tomato that is very popular in southeastern Spain. However, it is highly susceptible to several viruses, such as Tomato yellow leaf curl virus (TYLCV), which is considered one of the most important diseases of tomato crops and is a limiting factor for production in both outdoor and protected crops, making it difficult to eradicate. This study shows the effect of gene introgression on the performance of traditional lines of De la pera by combining two genes that offer tolerance to TYLCV, Ty-1 and ty-5, on some yield and quality traits and on the antioxidant capacity of tomato fruits. Two pear tomato breeding families, UMH175 and UMH220, were evaluated. Four lines from each of the families with all homozygous combinations of the Ty-1 and ty-5 genes were studied. The results showed that the introgression of the ty-5 allele produced a slight negative effect on yield, mean fruit weight, total soluble solids, and titratable acidity, in contrast to Ty-1, which produced a large negative effect. None of the introgressions showed a negative effect on the antioxidant compounds. ty-5 is a promising gene for use in breeding programs. Full article

Tomato yellow leaf curl virus (TYLCV) is a prominent viral pathogen that adversely affects tomato plants. Effective strategies for mitigating the impact of TYLCV include isolating tomato plants from the whitefly, which is the vector of the virus, and utilizing transgenic lines that are resistant to the virus. In our preliminary investigations, we observed that the use of growth retardants increased the rate of TYLCV infection and intensified the damage to the tomato plants, suggesting a potential involvement of gibberellic acid (GA) in the conferring of resistance to TYLCV. In this study, we employed an infectious clone of TYLCV to inoculate tomato plants, which resulted in leaf curling and growth inhibition. Remarkably, this inoculation also led to the accumulation of GA₃ and several other phytohormones. Subsequent treatment with GA₃ effectively alleviated the TYLCV-induced leaf curling and growth inhibition, reduced TYLCV abundance in the leaves, enhanced the activity of antioxidant enzymes, and lowered the reactive oxygen species (ROS) levels in the leaves. Conversely, the treatment with PP333 exacerbated TYLCV-induced leaf curling and growth suppression, increased TYLCV abundance, decreased antioxidant enzyme activity, and elevated ROS levels in the leaves. The analysis of the gene expression profiles revealed that GA₃ up-regulated the genes associated with disease resistance, such as WRKYs, NACs, MYBs, Cyt P450s, and ERFs, while it down-regulated the DELLA protein, a key agent in GA signaling. In contrast, PP333 induced gene expression changes that were the opposite of those caused by the GA₃ treatment. These findings suggest that GA plays an essential role in the tomato’s defense response against TYLCV and acts as a positive regulator of ROS scavenging and the expression of resistance-related genes. Full article