Mild Mottle Research Articles

Monitoring of SARS-CoV-2 concentration and circulation of variants of concern in wastewater of Leuven, Belgium.

Wastewater surveillance plays an important role in the management of the coronavirus disease 2019 (COVID-19) pandemic all over the world. Using different wastewater collection points in Leuven, we wanted to investigate the use of wastewater surveillance as an early warning system for an uprise of infections and as a tool to follow the circulation of specific variants of concern (VOCs) in particular geographic areas. Wastewater samples were collected from local neighborhood sewers and from a large regional wastewater treatment plant (WWTP) in the area of Leuven, Belgium. After virus concentration, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA was quantified by real-time quantitative polymerase chain reaction (RT-qPCR) and normalized with the human fecal indicator pepper mild mottle virus (PMMoV). A combination of multiplex RT-qPCR assays was used to detect signature mutations of circulating VOCs. Fecal virus shedding of SARS-CoV-2 variants was measured in feces samples of hospitalized patients. In two residential sampling sites, a rise in wastewater SARS-CoV-2 concentration preceded peaks in positive cases. In the WWTP, viral load peaks were seen concomitant with the consecutive waves of positive cases caused by the original Wuhan SARS-CoV-2 strain and subsequent VOCs. During the Omicron BA.1 wave, the wastewater viral load increased to a lesser degree, even after normalization of SARS-CoV-2 concentration using PMMoV. This might be attributable to a lower level of fecal excretion of this variant. Circulation of SARS-CoV-2 VOCs Alpha, Delta, Omicron BA1/BA.2, and BA.4/BA.5 could be detected based on the presence of specific key mutations. The shift in variants was noticeable in the wastewater, with key mutations of two different variants being present simultaneously during the transition period. Wastewater-based surveillance is a sensitive tool to monitor SARS-CoV-2 circulation levels and VOCs in larger regions. In times of reduced test capacity, this can prove to be highly valuable. Differences in excretion levels of various SARS-CoV-2 variants should however be taken into account when using wastewater surveillance to monitor SARS-CoV-2 circulation levels in the population.

Coding-Complete Sequence of Cowpea Mild Mottle Virus Isolated from Iraq.

Here, we report the coding-complete sequence of Cowpea mild mottle virus (CPMMV; strain Hilla) in cowpea using total transcriptome sequencing (RNA-seq) and bioinformatics analyses. The sequence length was 8,119 bp long and has 6 open reading frames. The genome was phylogenetically close to two isolates collected from Ghana.

Highly socially vulnerable communities exhibit disproportionately increased viral loads as measured in community wastewater

Wastewater surveillance has proven to be a useful tool for evidence-based epidemiology in the fight against the SARS-CoV-2 virus. It is particularly useful at the population level where acquisition of individual test samples may be time or cost-prohibitive. Wastewater surveillance for SARS-CoV-2 has typically been performed at wastewater treatment plants; however, this study was designed to sample on a local level to monitor the spread of the virus among three communities with distinct social vulnerability indices in Shreveport, Louisiana, located in a socially vulnerable region of the United States. Twice-monthly grab samples were collected from September 30, 2020, to March 23, 2021, during the Beta wave of the pandemic. The goals of the study were to examine whether: 1) concentrations of SARS-CoV-2 RNA in wastewater varied with social vulnerability indices and, 2) the time lag of spikes differed during wastewater monitoring in the distinct communities. The size of the population contributing to each sample was assessed via the quantification of the pepper mild mottle virus (PMMoV), which was significantly higher in the less socially vulnerable community. We found that the communities with higher social vulnerability exhibited greater viral loads as assessed by wastewater when normalized with PMMoV (Kruskal-Wallis, p < 0.05). The timing of the spread of the virus through the three communities appeared to be similar. These results suggest that interconnected communities within a municipality experienced the spread of the SARS-CoV-2 virus at similar times, but areas of high social vulnerability experienced more intense wastewater viral loads.

Potential risk of plant viruses entering disease cycle in surface water in protected vegetable growing areas of Eastern China.

With the expansion of protected vegetable growing areas (PVGAs), viral plant diseases have become more prevalent, causing severe economic losses to the vegetable production industry in China. At present, researches on plant viruses mainly focus on plants, but there is only a few reports on the species of viruses in surface water from PVGAs. The surface water samples in PVGAs are representative to a certain extent, which has an important reference value for studying the characteristics of plant viruses in surface water. The purpose of this study was to identify the diversity and the possibility of entering disease infection cycle of plant viruses in water samples collected from PVGAs in eastern China. A total of 144 water samples were collected, and eight plant viruses including tobacco mosaic virus (TMV, 8.33%), cucumber green mottle mosaic virus (CGMMV, 33.33%), pepper mild mottle virus (PMMoV, 6.94%), cucumber mosaic virus (CMV, 0.69%), tomato masaic virus (ToMV, 3.47%), tomato mottle mosaic virus (ToMMV, 0.69%), tomato chlorosis virus (ToCV, 4.17%), and tomato yellow leaf curl virus (TYLCV, 5.56%) were examined using RT-PCR and PCR. The species of viruses in surface water varied greatly by location. CGMMV, TMV, ToCV, ToMV, ToMMV, and TYLCV were identified in Shandong, a northern part of Eastern China, whereas only PMMoV was found in Shanghai, a southern part of Eastern China. After healthy tobacco plants were inoculated with the concentrated solutions of TMV, ToMV, CGMMV, and PMMoV, could cause disease in healthy tobacco, indicating that the plant viruses in the concentrated solution have the infectivity, and the plant viruses in surface water have the possibility of entering the infection cycle of disease. The results will improve the understanding of the potential risks of waterborne disease transmission.

Pepper Mild Mottle Virus: An Infectious Pathogen in Pepper Production and a Potential Indicator of Domestic Water Quality.

Pepper (Capsicum spp.; Family: Solanaceae; 2n = 24) is an important crop cultivated worldwide for the consumption of its fresh and dried processed fruits. Pepper fruits are used as raw materials in a wide variety of industrial processes. As a multipurpose vegetable crop, there is a need to increase the yield. However, yield productivity of pepper is severely constrained by infectious plant pathogens, including viruses, bacteria, fungi, and oomycetes. The pepper mild mottle virus (PMMoV) is currently one of the most damaging pathogens associated with yield losses in pepper production worldwide. In addition to impacts on pepper productivity, PMMoV has been detected in domestic and aquatic water resources, as well as in the excreta of animals, including humans. Therefore, PMMoV has been suggested as a potential indicator of domestic water quality. These findings present additional concerns and trigger the need to control the infectious pathogen in crop production. This review provides an overview of the distribution, economic impacts, management, and genome sequence variation of some isolates of PMMoV. We also describe genetic resources available for crop breeding against PMMoV.

Novel Cyclized Derivatives of Ferulic Acid as Potential Antiviral Agents through Activation of Photosynthesis

To further develop new antiviral agents, several novel cyclized derivatives of ferulic acid were designed and synthesized. Their antiviral activities were evaluated against the cucumber mosaic virus (CMV), pepper mild mottle virus (PMMoV), and tomato spotted wilt virus (TSWV). The results showed that some ferulic acid derivatives exhibited desirable antiviral activities. Particularly, compound 5e exhibited excellent protective activities against CMV, PMMoV, and TSWV, with EC50 values of 167.2, 102.5, and 145.8 μg mL-1, respectively, which were superior to those obtained for trans-ferulic acid (581.7, 611.2, and 615.4 μg mL-1), dufulin (312.6, 302.5, and 298.2 μg mL-1), and ningnanmycin (264.3, 282.5, and 276.5 μg mL-1). Thereafter, the protective mechanisms of 5e were evaluated through photosynthesis evaluation, transcriptome profiling, and proteomic analysis. The results indicated that 5e significantly activated the expression levels of photosynthesis-related regulatory genes and proteins in tobacco plants and promoted the accumulation of defense molecules to resist viral infection. Thus, the findings of this study indicated that novel cyclized ferulic acid derivatives are potential antiviral agents that act via regulating photosynthesis in the host.

Degradation rates influence the ability of composite samples to represent 24-hourly means of SARS-CoV-2 and other microbiological target measures in wastewater

The utility of using severe-acute respiratory syndrome coronavirus-2 (SARS-CoV-2) RNA for assessing the prevalence of COVID-19 within communities begins with the design of the sample collection program. The objective of this study was to assess the utility of 24-hour composites as representative samples for measuring multiple microbiological targets in wastewater, and whether normalization of SARS-CoV-2 by endogenous targets can be used to decrease hour to hour variability at different watershed scales. Two sets of experiments were conducted, in tandem with the same wastewater, with samples collected at the building, cluster, and community sewershed scales. The first set of experiments focused on evaluating degradation of microbiological targets: SARS-CoV-2, Simian Immunodeficiency Virus (SIV) – a surrogate spiked into the wastewater, plus human waste indicators of Pepper Mild Mottle Virus (PMMoV), Beta-2 microglobulin (B2M), and fecal coliform bacteria (FC). The second focused on the variability of these targets from samples, collected each hour on the hour. Results show that SARS-CoV-2, PMMoV, and B2M were relatively stable, with minimal degradation over 24-h. SIV, which was spiked-in prior to analysis, degraded significantly and FC increased significantly over the course of 24 h, emphasizing the possibility for decay and growth within wastewater. Hour-to-hour variability of the source wastewater was large between each hour of sampling relative to the variability of the SARS-CoV-2 levels calculated between sewershed scales; thus, differences in SARS-CoV-2 hourly variability were not statistically significant between sewershed scales. Results further provided that the quantified representativeness of 24-h composite samples (i.e., statistical equivalency compared against hourly collected grabs) was dependent upon the molecular target measured. Overall, improvements made by normalization were minimal within this study. Degradation and multiplication for other targets should be evaluated when deciding upon whether to collect composite or grab samples in future studies.

Serologic and molecular determination and phylogenetic analysis of some viruses infecting pepper in Turkey

Viruses are among the major agents causing yield loss in pepper production. During the 2016-2017, a survey was performed in pepperfields to determine of some viruses in pepper plants showing virus-like symptoms in different provinces of Turkey. Plant samples wereassayed using DAS-ELISA with specific antisera for cucumber mosaic virus (CMV), tomato spotted wilt virus (TSWV), tomato yellow leafcurl virus (TYLCV), alfalfa mosaic virus (AMV), and pepper mild mottle virus (PMMoV). The DAS-ELISA results indicated that 42.2, 17.5,17.5, and 10.6 of the 421 samples were infected with CMV, TSWV, AMV, and PMMoV, respectively. The positive samples were furtheranalysed by RT-PCR and sequencing. Based on sequence analyses, a phylogenetic tree was drawn for each of CMV, PMMoV and AMV.Phylogenetic analysis showed that CMV isolates were placed in subgroup IA within the major group I. The AMV isolates were classifiedwithin four clades and showed a high variability. PMMoV isolates were grouped with Serbia, Brazil, and Japan isolates within the group I.One AMW isolates determined possible recombinant isolates. Further studies needed for more information about recombinant isolatesand evolutions. The analyses of the molecular structure of viruses is important for the accurate diagnosis of the pathogen and to applythe right method of management strategies for controlling plant viruses in agriculture.

Controlling Pepper Mild Mottle Virus (PMMoV) Infection in Pepper Seedlings by Use of Chemically Synthetic Silver Nanoparticles

We investigated the roles of different concentrations of chemical synthetic spherical silver nanoparticles (AgNPs) in protecting pepper seedlings of the Mecca region, which were naturally and artificially infected by the pepper mild mottle virus (PMMoV). The virus shows many infection symptoms, including pepper leaf deformation with filiform leaves and severe mosaic symptoms. Our study focused on the antiviral activity of different concentrations of spherical nanoparticles in controlling PMMoV infecting pepper seedlings. PMMoV identification was confirmed via DAS-ELISA using the following antiserum: PMMoV, cucumber mosaic virus (CMV), tobacco mosaic virus (TMV), tomato mosaic virus (ToMV), potato virus Y (PVY), and tomato spotted wilt virus (TSWV). The presence of PMMoV was confirmed using electron microscopy and reverse transcription polymerase chain reaction (RT-PCR). We evaluated the effects of exogenously applied different concentrations of AgNPs on CMV infection rate, infection severity, virus concentration, and the concentrations of photosynthetic pigments chlorophyll a, chlorophyll b, carotenoid content, phenolic compounds, and protein components in virus-infected plant cells that were treated with three different concentration of nanoparticles (200, 300, and 400 µg/L) compared to the positive and negative control.

Effect of Populus nigra spring and autumn leaves extract on Capsicum annuum infected with pepper mild mottle virus

Capsicum annuum is one of the main vegetable crops for the local market and exportation in Egypt. In this concern, pepper mild mottle virus (PMMoV) infection caused a significant decrease in Capsicum sp. leading to large economic losses. An isolate of PMMoV was obtained from naturally infected pepper plants, exhibiting different patterns of mottling, leaf distortion, yellowing, and stunting of leaves. The virus was identified. The molecular detection of PMMoV was done using RT-PCR with specific primers designed for coat protein genes. An RT-PCR product (474) bp of the coat protein gene of (PMMoV) was cloned. The target of the investigation was the effect of spring and autumn ethanol extracts of Populus nigra leaves on C. annuum seedling growth and infected C. annuum with (PMMoV) under greenhouse conditions. The experimental data showed that treated spring leaf extract of P. nigra enhanced infected C. annuum seedling growth parameters and fruit quality compared to uninfected seedlings. P. nigra spring leaf extract containing some allo-chemicals had a negative effect on uninfected seedlings. P. nigra autumn leaf extract significantly improved the growth and fruit quality of infected C. annuum seedlings compared to the control.

A Simplified Multiplex PCR Assay for Simultaneous Detection of Six Viruses Infecting Diverse Chilli Species in India and Its Application in Field Diagnosis

Chilli is infected by at least 65 viruses globally, with a mixed infection of multiple viruses leading to severe losses being a common occurrence. A simple diagnostic procedure that can identify multiple viruses at once is required to track their spread, initiate management measures and manage them using virus-free planting supplies. The present study, for the first time, reports a simplified and robust multiplex PCR (mPCR) assay for the simultaneous detection of five RNA viruses, capsicum chlorosis orthotospovirus (CaCV), chilli veinal mottle virus (ChiVMV), large cardamom chirke virus (LCCV), cucumber mosaic virus (CMV), and pepper mild mottle virus (PMMoV), and a DNA virus, chilli leaf curl virus (ChiLCV) infecting chilli. The developed mPCR employed six pairs of primer from the conserved coat protein (CP) region of the respective viruses. Different parameters viz., primer concentration (150-450 nM) and annealing temperature (50 °C), were optimized in order to achieve specific and sensitive amplification of the target viruses in a single reaction tube. The detection limit of the mPCR assay was 5.00 pg/µL to simultaneously detect all the target viruses in a single reaction, indicating a sufficient sensitivity of the developed assay. The developed assay showed high specificity and showed no cross-amplification. The multiplex PCR assay was validated using field samples collected across Northeast India. Interestingly, out of 61 samples collected across the northeastern states, only 22 samples (36%) were positive for single virus infection while 33 samples (54%) were positive for three or more viruses tested in mPCR, showing the widespread occurrence of mixed infection under field conditions. To the best of our knowledge, this is the first report on the development and field validation of the mPCR assay for six chilli viruses and will have application in routine virus indexing and virus management.

Development and evaluation of TaqMan-based, one-step, real-time RT-PCR assays for pepper mild mottle virus detection for near source tracking and wastewater-based epidemiology validation.

Emergence of novel human pathogens pose significant challenges to human health as highlighted by the SARS-CoV-2 pandemic. Wastewater based epidemiology (WBE) has previously been employed to identify viral pathogens and outbreaks by testing samples from regional wastewater treatment plants. Near source tracking (NST) allows for more targeted WBE by analysing samples from individual buildings such as schools or even individual floors such as in multi-floor office buildings. Despite the public health advantages of WBE, few strategies exist for optimising NST sampling methodologies. Therefore, we developed a protocol to evaluate virus detection in NST sampling using Pepper Mild Mottle Virus (PMMoV) as a proxy for RNA viruses. PMMoV is the most abundant enteric human associated RNA virus and is present in peppers/pepper-containing foods. Two bespoke TaqMan RT-PCR assays were developed to detect a PMMoV genomic 5' region and a capsid associated gene. To evaluate the protocol against field samples, pepper homogenates were flushed down an in-use toilet (Liverpool School of Tropical Medicine, UK) to spike wastewater with PMMoV on multiple days, and samples collected from two sewage access points to validate NST samplers. These wastewater samples were assessed for PMMoV based on Ct values and results compared to pepper and Tabasco derived PMMoV positive controls. Positive detection of PMMoV was comparable and consistent in ten independent samples across two NST samplers regardless of pepper homogenate spiking. We have developed two novel one step TaqMan assays that amplify both PMMoV targets in viral RNA extractions from peppers, Tabasco, and wastewater samples with cDNA synthesis through to RT-PCR results taking approximately 30 minutes. Pepper homogenate flushing was not required to detect PMMoV in our wastewater samples, however this strategy of flushing PMMoV containing materials outlined here could be valuable in assessing and validating NST in buildings with no previous or current sewage flow.

High-throughput sequencing reveals the presence of novel and known viruses in diseased Paris yunnanensis.

Paris spp. are important medicinal plant and main raw material for many Chinese patent medicines, but viral diseases have became serious problems in cultivation of this group of important medicinal plants in China. In this study, eight viruses were identified in the diseased plants of Paris yunnanensis by high-throughput sequencing (HTS) and RT-PCR. These viruses include three novel viruses (two potyviruses and one nepovirus), Hippeastrum chlorotic ringspot virus (HCRV), Lychnis mottle virus (LycMoV), Paris mosaic necrosis virus (PMNV), Paris virus 1 and pepper mild mottle virus. The three new viruses were tentatively named Paris potyvirus 3 (ParPV-3), Paris potyvirus 4 (ParPV-4), Paris nepovirus 1 (ParNV-1) and their complete genome sequences were determined. Sequence analyses showed ParPV-3 and ParPV-4 shared the highest amino acid (aa) sequence identities of 54.3% to each other and 53.0-57.8% to other known potyviruses. ParNV-1 had aa sequence identities of 28.8-63.7% at protease-polymerase (Pro-Pol) with other nepoviruses. Phylogenetic analyses further support that the three viruses are new members of their corresponding genera. Analyses of the partial sequences of HCRV and LycMoV infecting P. yunnanensis revealed they diverged from existing isolates by aa sequence identities of 97.1% at glycoprotein precursor of HCRV and 93.3% at polyprotein of LycMoV. These two viruses are reported for the first time in Paris spp. A total of 123 field samples collected from P. yunnanensis in four counties of Yunnan, Southwest China were tested by RT-PCR for detecting each of the eight viruses. Results showed that nearly half of the samples were positive for at least one of the eight viruses. Two potyviruses, ParPV-3 (26.8%) and PMNV (24.4%), were predominant and widely distributed in the fields, while other viruses occurred in low rates and/or had limited distribution. This study insights into the virome infecting P. yunnanensis and provides valuable information for diagnosis and control of viral diseases in P. yunnanensis.

Expression of Concern: Pepper Mild Mottle Virus, a Plant Virus Associated with Specific Immune Responses, Fever, Abdominal Pains, and Pruritus in Humans.

Expression of Concern: Pepper Mild Mottle Virus, a Plant Virus Associated with Specific Immune Responses, Fever, Abdominal Pains, and Pruritus in Humans.

Application of the Human Viral Surrogate Pepper Mild Mottle Virus for Wastewater Fecal Pollution Management

Global water scarcity has led to significant dependence on reclaimed or recycled water for potable uses. Effluents arising from human and animal gut microbiomes highly influence water quality. Wastewater pollution is, therefore, frequently monitored using bacterial indicators (BI). However, threats to public health arise from the frequent incidence of wastewater-mediated viral infections–undetected by BI. Moreover, the enteric viromes contaminating wastewater are characterized by high abundance, genetic diversity and persistence in various water environments. Furthermore, humans usually suffer a minimum of a single acute diarrheal episode over their lifetime arising from extraneously acquired enteric microbiomes. A wide range of management methods are employed—in particular, microbial source tracking (MST) approaches to confront infections arising from exposure to contaminated wastewater. This review elaborates the viral contamination of treated wastewater and associated public health issues. Latterly, we discuss the various management strategies of wastewater pollution using conventional fecal indicators, viral indicators and human viral surrogates, with particular interest in the pepper mild mottle virus (PMMoV). Globally, PMMoV has been detected in rivers, aquifers, irrigation systems, and coastal and marine waters at high prevalence rates and concentrations greater than 105 genome copies per liter (gc/L). PMMoV was also found in almost all untreated wastewater environments. PMMoV concentrations in wastewater vary from 103 to 107 gc/L. These values are more than the maximum recorded viral indicator concentrations in wastewater for other proposed indicators. Limited variability in the daily concentrations of PMMoV in fecal wastewater has been studied, with an estimated average concentration of 105 gc/L with insignificant seasonal variability. The information summarized in this article offers fundamental knowledge for decision making in terms of defining the suitability criteria of candidate fecal indicators, risk assessment application and efficient wastewater management.

Updates on cowpea viruses in Southwest Nigeria: distribution, prevalence and coinfection.

The online version contains supplementary material available at 10.1007/s42360-022-00576-8.

Elicitation of Hyoscyamine Production in Datura stramonium L. Plants Using Tobamoviruses

Datura stramonium L. produces tropane alkaloids, and the hyoscyamine is dominant among them. Hyoscyamine is produced by hairy root cultures in vitro derived from native plants or plants with the genetically modified biosynthetic pathway for hyoscyamine. A common procedure is extraction from cultivated plants. Elicitors for increased production can be used in both cases. Live viruses are not well known for use as elicitors, therefore, D. stramonium plants grown in soil were artificially infected with the tobamoviruses Pepper mild mottle virus (PMMoV), Tomato mosaic virus (ToMV), and Tobacco mosaic virus (TMV). Differences in the content of hyoscyamine were between capsules and roots of infected and non-infected plants. Elicitation increased content of hyoscyamine in capsules 1.23-2.34 times, compared to the control. The most effective viruses were PMMoV and ToMV (isolate PV143), which increased content to above 19 mg/g of fresh weight of a capsule. The effect of each virus elicitor was expressed also in hyoscyamine content in roots. Elicited plants contained 5.41-16.54 times more hyoscyamine in roots compared to non-elicited plants. The most effective elicitor was ToMV SL-1, which raised production above 20 mg/g fresh weight of roots. It has been shown that tobamoviruses can be used as biotic elicitors.

Inhibitory Effects of Pepper Mild Mottle Virus Infection by Supernatants of Five Bacterial Cultures in Capsicum annuum L.

Pepper mild mottle virus (PMMoV), one of the most prevalent viruses in chili pepper (Capsicum annuum L.) is a non-enveloped, rod-shaped, single-stranded positive-sense RNA virus classified in the genus Tobamovirus. The supernatants of five bacterial cultures (Pseudomonas putida [PP], Bacillus licheniformis [BLI], P. fluorescens [PF], Serratia marcescens [SER], and B. amyloliquifaciens [BA]) were analyzed to find novel antiviral agents to PMMoV in chili pepper. Foliar spraying with supernatants (1:1, v/v) obtained from Luria-Bertani broth cultures of PP, BLI, PF, SER, and BA inhibited PMMoV infection of chili pepper if applied before the PMMoV inoculation. Double-antibody sandwich enzyme-linked immunosorbent assay showed that treatments of five supernatants resulted in 51-66% reductions in PMMoV accumulation in the treated chili pepper. To identify key compounds in supernatants of PP, BLI, PF, SER, and BA, the supernatants were subjected to gas chromatography-mass spectrometry. The 24 different types of compounds were identified from the supernatants of PP, BLI, PF, SER, and BA. The compounds vary from supernatants of one bacterial culture to another which includes simple compounds-alkanes, ketones, alcohols, and an aromatic ring containing compounds. The compounds triggered the inhibitory effect on PMMoV propagation in chili pepper plants. In conclusion, the cultures could be used to further conduct tissue culture and field trial experiments as potential bio-control agents.

Reversion of a resistance-breaking mutation shows reversion costs and high virus diversity at necrotic local lesions.

An instance of host range evolution relevant to plant virus disease control is resistance breaking. Resistance breaking can be hindered by across-host fitness trade-offs generated by negative effects of resistance-breaking mutations on the virus fitness in susceptible hosts. Different mutations in pepper mild mottle virus (PMMoV) coat protein result in the breaking in pepper plants of the resistance determined by the L3 resistance allele. Of these, mutation M138N is widespread in PMMoV populations, despite associated fitness penalties in within-host multiplication and survival. The stability of mutation M138N was analysed by serial passaging in L3 resistant plants. Appearance on passaging of necrotic local lesions (NLL), indicating an effective L3 resistance, showed reversion to nonresistance-breaking phenotypes was common. Most revertant genotypes had the mutation N138K, which affects the properties of the virus particle, introducing a penalty of reversion. Hence, the costs of reversion may determine the evolution of resistance-breaking in addition to resistance-breaking costs. The genetic diversity of the virus population in NLL was much higher than in systemically infected tissues, and included mutations reported to break L3 resistance other than M138N. Infectivity assays on pepper genotypes with different L alleles showed high phenotypic diversity in respect to L alleles in NLL, including phenotypes not reported in nature. Thus, high diversity at NLL may potentiate the appearance of genotypes that enable the colonization of new host genotypes or species. Collectively, the results of this study contribute to better understanding the evolutionary dynamics of resistance breaking and host-range expansions.

Genome characterisation of two complete coding sequences of tomato mild mottle virus from tree tomato and their distribution in Kenya

Genome characterisation of two complete coding sequences of tomato mild mottle virus from tree tomato and their distribution in Kenya