Plant Virus Diseases Research Articles

Detection of Plant Viruses and Disease Management: Relevance of Genetic Diversity and Evolution.

Plant viruses cause considerable economic losses and are a threat for sustainable agriculture. The frequent emergence of new viral diseases is mainly due to international trade, climate change, and the ability of viruses for rapid evolution. Disease control is based on two strategies: i) immunization (genetic resistance obtained by plant breeding, plant transformation, cross-protection, or others), and ii) prophylaxis to restrain virus dispersion (using quarantine, certification, removal of infected plants, control of natural vectors, or other procedures). Disease management relies strongly on a fast and accurate identification of the causal agent. For known viruses, diagnosis consists in assigning a virus infecting a plant sample to a group of viruses sharing common characteristics, which is usually referred to as species. However, the specificity of diagnosis can also reach higher taxonomic levels, as genus or family, or lower levels, as strain or variant. Diagnostic procedures must be optimized for accuracy by detecting the maximum number of members within the group (sensitivity as the true positive rate) and distinguishing them from outgroup viruses (specificity as the true negative rate). This requires information on the genetic relationships within-group and with members of other groups. The influence of the genetic diversity of virus populations in diagnosis and disease management is well documented, but information on how to integrate the genetic diversity in the detection methods is still scarce. Here we review the techniques used for plant virus diagnosis and disease control, including characteristics such as accuracy, detection level, multiplexing, quantification, portability, and designability. The effect of genetic diversity and evolution of plant viruses in the design and performance of some detection and disease control techniques are also discussed. High-throughput or next-generation sequencing provides broad-spectrum and accurate identification of viruses enabling multiplex detection, quantification, and the discovery of new viruses. Likely, this technique will be the future standard in diagnostics as its cost will be dropping and becoming more affordable.

Carlaviral load distribution in hop plants (Humulus lupulus L.)

Knowledge of viral load distribution in a plant is important both for virological research on the whole and for the production of virus-free planting material in particular. At the same time, development of preventive measures for plant virus diseases is no less important. Thus, the purpose of this study was to investigate the viral load distribution of carlaviruses in hop plants (Humulus lupulus L.), as well as to test effective measures to stimulate the growth and development and prevention of the spread of hop viruses. In this study, virological, cytological, botanical and ecological methods were applied. This paper reports on the research results of viral load distribution of carlaviruses in hop plants as well as efficiency of clinorotation, biocomposition Bioecofunge-1, and cerium dioxide nanoparticles use in hop growing. It was found that during the growing season, the largest accumulation of carlaviruses was observed in leaves and young shoots at the top of the stem (at a distance of 150–200 cm from the ground), while in winter, the largest accumulation of carlaviruses was observed in the buds of the etiolated underground shoots. In this study also found that the effective measure to stimulate the growth and development of hop plants, as well as the prevention of the spread of hop carlaviruses was the combined use of biocomposition Bioecofunge-1 and cerium dioxide nanoparticles, which led to a 32% increase in the root system. We also found that the clinorotation promotes healing and stimulates the growth and development of hops. At the same time, it should be noted that in this study was only identified to the genus of both hop carlaviruses and hop ilaviruses and that these viruses formed mixed infections, should therefore be conducted further research in conditions of mono-infections.

Emerging plant viruses in cotton

Plants usually suffer from parasitic and non parasitic diseases in the world. One of the major groups that cause infections in plants belong to viruses, which is obligate parasite and replicate only in living cells. They are generally insect or seed transmitted and changes associated with global warming may affect both their incidence and severity. New virus diseases that are threatening the world’s agricultural production are called “emerging diseases” which are commonly detected on different crop plants. Recent emerging viruses have RNA or DNA genome and belong to Potyviridae, Bunyaviridae, Geminiviridae, Closteroviridae, Betaflexiviridae and Secoviridae families. Plant virus diseases, like diseases caused by other pathogens, appear to be proliferating at ever increasing rates. Scientific and popular media abound with terms such as new, emerging, re-emerging and threatening plant diseases. In the present paper, the emerging viral diseases reported in cotton were discussed in detail.

Modelling the Effect of Incubation and Latent Periods on the Dynamics of Vector-Borne Plant Viral Diseases.

Most of the plant viral diseases spread through vectors. In case of the persistently transmitted disease, there is a latent time of infection inside the vector after acquisition of the virus from the infected plant. Again, the plant after getting infectious agent shows an incubation time after the interaction with an infected vector before it becomes diseased. The goal of this work is to study the effect of both incubation delay and latent time on the dynamics of plant disease, and accordingly a delayed model has been proposed. The existence of the equilibria, basic reproductive number ([Formula: see text]) and stability of equilibria have been studied. This study shows the relevance of the presence of two time delays, which may lead to system stabilization.

Efficiency of potato and garlic virus control by interferon use

Efficiency of potato and garlic virus control by interferon use

Synthetic chloroinconazide compound exhibits highly efficient antiviral activity against tobacco mosaic virus.

Development of anti-plant-virus compounds and improvement of biosafety remain hot research topics in controlling plant viral disease. Tobacco mosaic virus (TMV) infects all tobacco species as well as many other plants worldwide and causes severe losses in tobacco production. To date, no efficient chemical treatments are known to protect plants from virus infection. Therefore, the search for a highly active antiviral compound with high efficacy in field application is required. We reported the synthesis of a novel antiviral halogenated acyl compound Chloroinconazide (CHI) using tryptophan as a substrate and examined its anti-TMV activity. We found that CHI displayed the ability to strongly inhibit the infection of TMV on Nicotiana benthamiana via multiple mechanisms. We observed that CHI was able to impair the virulence of TMV by directly altering the morphological structure of virions and increasing the activity of anti-oxidative enzymes, resulting in reduced TMV-induced ROS production during infection of the plant. In addition, the expression of salicylic acid-responsive genes was significantly increased after CHI application. However, after application of CHI on SA-deficient NahG plants no obvious anti-TMV activity was observed, suggesting that the SA signaling pathway was required for CHI-induced anti-TMV activity associated with reduced infection of TMV. CHI exhibited no effects on plant growth and development. The easily synthesized CHI can actively induce plant resistance against TMV as well as act on virus particles and exhibits high biosafety, which provides a potential for commercial application of CHI in controlling plant virus disease in the future. © 2020 Society of Chemical Industry.

Distribution and evolution of the major viruses infecting cucurbitaceous and solanaceous crops in the French Mediterranean area

Plant viral diseases represent a significant burden to plant health, and their highest impact in Mediterranean agriculture is on vegetables grown under intensive horticultural practices. In order to understand better virus evolution and emergence, the most prevalent viruses were mapped in the main cucurbitaceous (melon, squashes) and solanaceous (tomato, pepper) crops and in some wild hosts in the French Mediterranean area, and virus diversity, evolution and population structure were studied through molecular epidemiology approaches. Surveys were performed in summer 2016 and 2017, representing a total of 1530 crop samples and 280 weed samples. The plant samples were analysed using serological and molecular approaches, including high-throughput sequencing (HTS). The viral species and their frequency in crops were quite similar to those of surveys conducted ten years before in the same areas. Contrary to other Mediterranean countries, aphid-transmitted viruses remain the most prevalent in France whereas whitefly-transmitted ones have not yet emerged. However, HTS analysis of viral evolution revealed the appearance of undescribed viral variants, especially for watermelon mosaic virus (WMV) in cucurbits, or variants not present in France before, as for cucumber mosaic virus (CMV) in solanaceous crops. Deep sequencing also revealed complex virus populations within individual plants with frequent recombination or reassortment. The spatial genetic structure of cucurbit aphid-borne yellows virus (CABYV) was related to the landscape structure, whereas in the case of WMV, the recurrence of introduction events and probable human exchanges of plant material resulted in complex spatial pattern of genetic variation.

The Potential Risk of Plant-Virus Disease Initiation by Infected Tomatoes.

During 2019, tomato fruits showing viral-like symptoms of marbled yellow spots were abundant in Israel. The new symptoms were distinctive from those typical of tomato brown rugose fruit virus (ToBRFV) infection but resembled symptoms of pepino mosaic virus (PepMV) infection. RT-PCR analysis and the serological tests (enzyme linked immunosorbent assay, western blot and in situ immunofluorescence) revealed and confirmed the presence of both the tobamovirus ToBRFV and the potexvirus PepMV in the symptomatic fruits. A mixture of rod-like and filamentous particles, characteristic of viruses belonging to tobamovirus and potexvirus genera, was visualized by transmission electron microscopy of the tomato fruit viral extract. Sanger sequencing of amplified PepMV-coat protein gene segments showed ~98% sequence identity to the Chilean (CH2)-strain. In a biological assay testing the contribution of traded infected tomatoes to the establishment of tomato plant disease, we applied direct and indirect inoculation modes using Tm-22-resistant tomato plants. The results, assessed by disease symptom development along with serological and molecular analyses, showed that the ToBRFV and PepMV co-infected fruits were an effective inoculum source for disease spread only when fruits were damaged. Importantly, intact fruits did not spread the viral disease. These results added a new factor to disease epidemiology of these viruses.

Nitric Oxide Enhances Rice Resistance to Rice Black-Streaked Dwarf Virus Infection

BackgroundRice black-streaked dwarf virus (RBSDV) causes one of the most important rice virus diseases of plants in East Asia. However, molecular mechanism(s)controlling rice resistance to infection is largely unknown.ResultsIn this paper, we showed that RBSDV infection in rice significantly induced nitric oxide (NO) production. This finding was further validated through a genetic approach using a RBSDV susceptible (Nipponbare) and a RBSDV resistant (15HPO187) cultivar. The production of endogenous NO was muchhigher in the 15HPO187 plants, leading to a much lower RBSDV disease incidence. Pharmacological studies showed that the applications of NO-releasingcompounds (i.e., sodium nitroprusside [SNP] and nitrosoglutathione [GSNO]) to rice plants reduced RBSDV disease incidence. After RBSDV infection, the levels of OsICS1, OsPR1b and OsWRKY 45 transcripts were significantly up-regulated by NO in Nipponbare. The increased salicylic acid contents were also observed. After the SNP treatment, protein S-nitrosylation in rice plants was also increased, suggesting that the NO-triggered resistance to RBSDV infection was partially mediated at the post-translational level. Although Osnia2 mutant rice produced less endogenous NO after RBSDV inoculation and showed a higher RBSDV disease incidence, its RBSDV susceptibility could be reduced by SNP treatment.ConclusionsCollectively, our genetic and molecular evidence revealed that endogenous NO was a vital signal responsible for rice resistance to RBSDV infection.

Control of mosaic disease using microbial biostimulants: insights from mathematical modelling

A major challenge to successful crop production comes from viral diseases of plants that cause significant crop losses, threatening global food security and the livelihoods of countries that rely on those crops for their staple foods or source of income. One example of such diseases is a mosaic disease of plants, which is caused by begomoviruses and is spread to plants by whitefly. In order to mitigate negative impact of mosaic disease, several different strategies have been employed over the years, including roguing/replanting of plants, as well as using pesticides, which have recently been shown to be potentially dangerous to the environment and humans. In this paper we derive and analyse a mathematical model for control of mosaic disease using natural microbial biostimulants that, besides improving plant growth, protect plants against infection through a mechanism of RNA interference. By analysing the stability of the system’s steady states, we will show how properties of biostimulants affect disease dynamics, and in particular, how they determine whether the mosaic disease is eradicated or is rather maintained at some steady level. We will also present the results of numerical simulations that illustrate the behaviour of the model in different dynamical regimes, and discuss biological implications of theoretical results for the practical purpose of control of mosaic disease.

Antibiotics- A Miracle Drug as Crop Protectants: A Review

Antibiotics known as the drugs of wonder seem to have long run since olden times as significant in its application towards agriculture. Antibiotics have its application to control bacterial, fungal, viral and phytoplasmal diseases of high valued tree crops and plants of ornamental in nature. The laws of drug in various countries differ distress over use of antibiotics as crop protectants. The main concern related to use of antibiotics is appropriate and hence more information is needed over the effectiveness and safety use of antibiotics in controlling plant diseases. Development of antibiotic resistance in plant-pathogenic bacteria alarmed problem in the agro pathosystems where it have been used for many years in disease control programs. The efficacy of antibiotics to control plant diseases has been diminished due to the emergence of antibiotic-resistant strains for the particular pathogens. Inspite of negative aspect, the antibiotics seems to continue important tools for the management of the important devastating plant diseases.

Plant virology: Alive and kicking!

Plant virology: Alive and kicking!

Synthesis of Four Optical Isomers of Antiviral Agent NK0209 and Determination of Their Configurations and Activities against a Plant Virus.

Previously, we reported for the first time that harmala alkaloids harmine and tetrahydroharmine exhibit activity against plant viruses, and we developed an analogue, designated NK0209, that efficiently prevents and controls plant virus diseases. Here, to investigate the influence of the spatial configuration of NK0209 on its antiviral activities, we synthesized its four optical isomers, determined their configurations, and evaluated their activities against tobacco mosaic virus. All four isomers were significantly more active than ningnanmycin, which is one of the most successful commercial antiviral agents, with in vivo inactivation, cure, and protection rates of 57.3 ± 1.9, 54.2 ± 3.3, and 55.0 ± 4.1% at 500 μg/mL. Furthermore, analysis of structure-activity relationships demonstrated for the first time that the spatial conformation of NK0209 is an important determinant of its antiviral activity, and our results provide information about the possible optimum configuration for interaction of this molecule with its target protein.

Manipulation of Jasmonate Signaling by Plant Viruses and Their Insect Vectors.

Plant viruses pose serious threats to stable crop yield. The majority of them are transmitted by insects, which cause secondary damage to the plant host from the herbivore-vector’s infestation. What is worse, a successful plant virus evolves multiple strategies to manipulate host defenses to promote the population of the insect vector and thereby furthers the disease pandemic. Jasmonate (JA) and its derivatives (JAs) are lipid-based phytohormones with similar structures to animal prostaglandins, conferring plant defenses against various biotic and abiotic challenges, especially pathogens and herbivores. For survival, plant viruses and herbivores have evolved strategies to convergently target JA signaling. Here, we review the roles of JA signaling in the tripartite interactions among plant, virus, and insect vectors, with a focus on the molecular and biochemical mechanisms that drive vector-borne plant viral diseases. This knowledge is essential for the further design and development of effective strategies to protect viral damages, thereby increasing crop yield and food security.

Novel combined biological antiviral agents Cytosinpeptidemycin and Chitosan oligosaccharide induced host resistance and changed movement protein subcellular localization of tobacco mosaic virus

Plant viral diseases cause severe economic losses in agricultural production. Development of microorganism-derived antiviral agents provides an alternative strategy to efficiently control plant viral diseases. In this study, the antiviral effect and mechanism of a combined biological agent Cytosinpeptidemycin and Chitosan oligosaccharide (CytPM-COS) were investigated. CytPM-COS effectively inhibited tobacco mosaic virus (TMV) in Nicotiana glutinosa, suppressed viral RNA and CP accumulation in BY-2 protoplast and affected the subcellular localization as well as punctate formation of TMV MP in N. benthamiana leaves. In addition, CytPM-COS triggered reactive oxygen species (ROS) production and induced up-regulation of various defense responsive genes including PR-1, PR-5, FLS2, Hsp70. Our results indicated that CytPM-COS can potentially act as a pesticide for integrated control of plant viruses in the future.

Identification of resistant sources in chilli (Capsicum sp.) genotypes to Groundnut bud necrosis virus (GBNV)

Chilli pepper (Capsicum annuum L.) is an important commercial crop grown on the Indian subcontinent. Recently, its production has been limited due to the incidence of thrips transmitting the Groundnut bud necrosis virus (GBNV). Constraint of such viral pathogens is challenging due to their broad host range and also ineffective chemical means to control the vector populations. The use of resistant cultivars is the most effective and in many cases the only strategy to limit plant viral diseases. In order to search for resistance sources in chilli peppers, a total of 102 Capsicum genotypes were screened for GBNV resistance through mechanical inoculation. Out of the 102 genotypes screened for GBNV resistance, none showed immune reaction, eight genotypes were highly resistant, eight lines were resistant, seven were intermediate resistant and the remaining 79 genotypes showed susceptible reaction on the five-point disease scale. The viral resistance reaction of chilli genotypes was measured based on symptomatology, DAC-ELISA and PCR testing. The highest per cent disease incidence was observed in IC393723 (100%) with an ELISA absorbance (A405) value of 3.03. The lowest per cent disease incidence was observed in eight genotypes viz., EC631810, IIHR4360, IIHR4577, IIHR4578, IIHR4582, IIHR4585, IIHR4587 and IIHR4588 with no symptoms or a few local lesions on the inoculated leaves, with ELISA absorbance values of less than 0.30 and are positive for GBNV RT-PCR testing. These genotypes can be further used in chilli crop improvement programs to develop GBNV resistant cultivars.

Melatonin is responsible for rice resistance to rice stripe virus infection through a nitric oxide-dependent pathway

Rice stripe virus (RSV) causes one of the most important rice virus diseases of plants in East Asia. However, the molecular mechanisms controlling rice resistance to RSV infection are largely unknown. Recently, several studies presented a novel model that melatonin (MT) and nitric oxide (NO) participate in the plant-pathogen interaction in a synergetic manner. In this study, there was a difference in MT content between two rice varieties that correlated with one being susceptible and one being resistant to RSV, which suggested that MT is related to RSV resistance. In addition, a test with two NO biosynthesis inhibitors revealed that NO inhibitor were able to increase the disease incidence of RSV. A pharmacological experiment with exogenous MT and NO showed that increased MT and NO in the MT-pretreated plants led to lower disease incidences; however, only NO increased in a NO-releasing reagent [sodium nitroprusside (SNP)] pretreated plants. The expressions level of OsPR1b and OsWRKY 45 were significantly induced by MT and NO. These results suggest that rice resistance to RSV can be improved by increased MT through a NO-dependent pathway.

Trends and gaps in forecasting plant virus disease risk

Trends and gaps in forecasting plant virus disease risk

Streptomyces spp. culture filtrates reduced T4 infectivity to E. coli

A Streptomyces spp. culture was isolated and identified. Its filtrate was found to be able to destroy ORSV and CYmMV virus coat protein, and could be used to reduce the transmission of plant virus disease in vivo, in our previous study. We also tested and found that it can destroy the coat proteins of 13 other of plant viruses, suggesting that the mechanism of action is not specific to a few plant viruses. Aim: To test if this culture filtrate can destroy or affect the infectivity of non-plant viruses. Materials and methods: Streptomyces spp. were cultured in soybean-based culture medium for 14 days, and the culture was collected and filtered. T4 phage infection of E. coli was used as a model. E. coli was cultured on 0.75% TSA agar plates. The T4 phage was incubated with various concentrations of Streptomyces spp culture filtrate for 30 minutes, before adding to the E. coli lawn. Culture filtrates of two strains, the C5-6 and the SML-1, were used. T4 phage incubated with 300 ppm virusbom (a known anti-viral agent) was used as a positive control. The formation of T4 lysis colony was calculated for the plaque-forming unit (PFU). Results: The dilution of 1 in 8 of the culture filtrates reduced the number of phage colony on E. coli lawn. The infectivity was significantly reduced when T4 was incubated with the culture filtrate at 1/8 dilution when compared to the non-treated groups. The virusbom treated PFU was significantly reduced, in comparison with C5-6 treated group (P=0.013), and with SML-1 treated group (P=0.028) as per ANOVA test followed by Tukey post-hoc comparison. Summary: These data demonstrated that culture filtrates of Streptomyces spp. reduced T4 to E. coli infectivity and suggested that the anti-viral compounds in the filtrate is not specific to plant viruses. The application of the culture filtrate and its content might have broader applications.

Comparison of viral infection risk between organic and conventional crops of tomato in Spain

The harmful effects of conventional agriculture on the environment and human health have been an increasing concern, resulting in the search for alternative and more sustainable agricultural systems in the last decades. Organic farming is the fastest growing system worldwide, but there is a controversial debate on the ability of the agroecological practices to cope with diseases and pests and produce food for the world population. However, comparative studies on the effect of organic farming on plant disease are almost non-existent particularly concerning plant virus diseases. In this work, a survey of Tomato mosaic virus (ToMV), Cucumber mosaic virus (CMV) and Tomato spotted wilt virus (TSWV) was performed in tomato crops under organic or conventional management by sampling 40 small farms in Eastern Spain. ToMV had the highest incidence whereas few plants were infected by CMV and none by TSWV. Viral infection risk was estimated as the probability of a plant being infected by at least one of the three viruses or by each virus separately according to a Bayesian logistic regression model. Our analysis showed that the infection risk by these viruses was lower in organic than in conventional farms in two non-consecutive years.