Tobacco Mosaic Virus Research Articles

Effects of seed treatment on cassava stake performance, whitefly population, disease incidence, and yield performance of cassava (Manihot esculenta Crantz) in Malawi

IntroductionWhitefly (Bemisia tabaci) is a pest of cassava (Manihot esculenta Crantz) and the vector for two of the crop’s major viral diseases – cassava mosaic disease (CMD) and cassava brown streak disease (CBSD), causing severe economic losses for farmers. In this context, we conducted an on-farm experiment to study the efficiency of a seed treatment technology containing thiamethoxam, fludioxonil, and metalaxyl for rapid multiplication of superior cassava genotypes and early protection of the crop against whitefly at Salima and Nkhotakota, central Malawi in the 2019/2020 and 2020/2021 cropping seasons, respectively.MethodsThe trials were conducted using a randomized complete block design with four replicates. The effect of the application of the seed treatment on stake germination, whitefly population, CMD and CBSD incidences, and stem and storage root yields of three cassava varieties (Kalawe, Mbundumali, and Sauti) at three stake sizes (8 cm, 16 cm, and 25 cm) was compared with control – a 25 cm stake size of each of the cassava variety without seed treatment. A benefit-cost analysis was conducted to determine the profitability of the seed treatment technology for each stake size under certified and non-certified stem scenarios.Results and discussionRegardless of stake size and variety, plant germination was highest (96% by 16%) and mean whitefly population lowest (adult 0.4 vs. 3.0 plant-1; nymph 1.0 vs. 3.3 plant-1) with seed treatment application than without. Disease incidence measurements showed no significant effect of seed treatment on CBSD control (p = 0.31), but it reduced CMD incidence by 17% vs. 20% in the untreated. Stem and storage root yields across stake size and cassava variety were highest with seed treatment; 489 bundles ha-1 and 10 (DM) Mg ha-1, respectively. Using the 8 cm stake regardless of variety resulted in the highest average benefit-cost ratio for certified (18.3 USD USD-1) and non-certified (7.8 USD USD-1) cassava stem scenarios.ConclusionWe conclude that the application of the seed treatment tested in this study would offer protection to planted stakes, increase their germination, reduce whitefly population, increase stem and storage root yields in areas experiencing whitefly pressure, and result in high economic profits.

Genetics, genomics, and breeding of black gram [Vigna mungo (L.) Hepper

Black gram [Vigna mungo (L.) Hepper] is a highly nutritious grain legume crop, mainly grown in South and Southeast Asia, with the largest area in India, where the crop is challenged by several biotic and abiotic stresses leading to significant yield losses. Improving genetic gains to increase on-farm yields is the primary goal of black gram breeding programs. This could be achieved by developing varieties resistant to major diseases like mungbean yellow mosaic disease, urdbean leaf crinkle virus, Cercospora leaf spot, anthracnose, powdery mildew, and insect pests such as whitefly, cowpea aphids, thrips, stem flies, and bruchids. Along with increasing on-farm yields, incorporating market-preferred traits ensures the adoption of improved varieties. Black gram breeding programs rely upon a limited number of parental lines, leading to a narrow genetic base of the developed varieties. For accelerating genetic gain, there is an urgent need to include more diverse genetic material for improving traits for better adaptability and stress resistance in breeding populations. The present review summarizes the importance of black gram, the major biotic and abiotic stresses, available genetic and genomic resources, major traits for potential crop improvement, their inheritance, and the breeding approaches being used in black gram for the development of new varieties.

Direct Detection of Tobacco Mosaic Virus in Infected Plants with SERS-Sensing Hydrogels.

The impact of plant pathogens on global crop yields is a major societal concern. The current agricultural diagnostic paradigm involves either visual inspection (inaccurate) or laboratory molecular tests (burdensome). While field-ready diagnostic methods have advanced in recent years, issues remain with detection of presymptomatic infections, multiplexed analysis, and requirement for in-field sample processing. To overcome these issues, we developed surface-enhanced Raman scattering (SERS)-sensing hydrogels that detect pathogens through simple contact with a leaf. In this work, we developed a novel reagentless SERS sensor for the detection of tobacco mosaic virus (TMV) and embedded it in an optimized hydrogel material to produce sensing hydrogels. To test the diagnostic application of our sensing hydrogels, we demonstrate their use to detect TMV infection in tobacco plants. This technology has the potential to shift the current agricultural diagnostic paradigm by offering a field-deployable tool for presymptomatic and multiplexed molecular identification of pathogens.

Non-transgenic, PAMAM co-delivery DNA of interactive proteins NbCRVP and NbCalB endows Nicotiana benthamiana with a stronger antiviral effect to RNA viruses

BackgroundViral diseases continue to pose a major threat to the world’s commercial crops. The in-depth exploration and efficient utilization of resistance proteins have become crucial strategies for their control. However, current delivery methods for introducing foreign DNA suffer from host range limitations, low transformation efficiencies, tissue damage, or unavoidable DNA integration into the host genome. The nanocarriers provides a convenient channel for the DNA delivery and functional utilization of disease-resistant proteins.ResultsIn this research, we identified a cysteine-rich venom protein (NbCRVP) in Nicotiana benthamiana for the first time. Virus-induced gene silencing and transient overexpression clarified that NbCRVP could inhibit the infection of tobacco mosaic virus, potato virus Y, and cucumber mosaic virus, making it a broad-spectrum antiviral protein. Yeast two-hybrid assay, co-immunoprecipitation, and bimolecular fluorescence complementation revealed that calcium-dependent lipid-binding (CaLB domain) family protein (NbCalB) interacted with NbCRVP to assist NbCRVP playing a stronger antiviral effect. Here, we demonstrated for the first time the efficient co-delivery of DNA expressing NbCRVP and NbCalB into plants using poly(amidoamine) (PAMAM) nanocarriers, achieving stronger broad-spectrum antiviral effects.ConclusionsOur work presents a tool for species-independent transfer of two interacting protein DNA into plant cells in a specific ratio for enhanced antiviral effect without transgenic integration, which further demonstrated new strategies for nanocarrier-mediated DNA delivery of disease-resistant proteins.Graphical abstract

Pathological and genome assembly of transcriptome sequencing data implied multiple relationships between bean common mosaic virus (BCMV), Batocera lineolata and aphids in Populus alba var. pyramidalis

This paper reports a novel poplar mosaic disease that occurred on the leaves of Populus alba var. pyramidalis in China. Symptoms: mosaic and chlorosis leaves, leaf abscission, leaf and young branch withering, leaf growth retard, and the destroyed and hollowed cell structures of mesophyll cells in the diseased leaves. Electron microscopy observation showed that some typical (flexible rods, virus particles 10–14 nm in width, and ca. 700 nm in length) and atypical virus particles (1400 or 2000 nm in length) of genus Potyvirus were found in the leaf exudates of the diseased poplar. De novo assembly assembled a nearly complete genome sequence of bean common mosaic virus (BCMV, 10035 nt in length) from the transcriptome sequencing data of poplar leaves. Moreover, field observation illustrated that two larvae of white-striped longhorn beetle (Batocera lineolata) inhabited and almost completely destroyed the main branch and roots of the diseased poplar plant, and a high-density population of two Chaitophorus aphid species once infected poplar plants before the occurrence of mosaic symptoms. Results suggested that BCMV is the pathogen of this novel poplar mosaic disease; moreover, results also suggested beetle and aphids that might involve in the occurrence and development of poplar mosaic disease.

Enhanced Resistance to Viruses in Nicotiana edwardsonii 'Columbia' Is Dependent on Salicylic Acid, Correlates with High Glutathione Levels, and Extends to Plant-Pathogenic Bacteria and Abiotic Stress.

Our earlier research showed that an interspecific tobacco hybrid (Nicotiana edwardsonii 'Columbia' [NEC]) displays elevated levels of salicylic acid (SA) and enhanced resistance to localized necrotic symptoms (hypersensitive response [HR]) caused by tobacco mosaic virus (TMV) and tobacco necrosis virus (TNV), as compared with another interspecific hybrid (Nicotiana edwardsonii [NE]) derived from the same parents. In the present study, we investigated whether symptomatic resistance in NEC is indeed associated with the inhibition of TMV and TNV and whether SA plays a role in this process. We demonstrated that enhanced viral resistance in NEC is manifested as both milder local necrotic (HR) symptoms and reduced levels of TMV and TNV. The presence of an adequate amount of SA contributes to the enhanced defense response of NEC to TMV and TNV, as the absence of SA resulted in seriously impaired viral resistance. Elevated levels of subcellular tripeptide glutathione (GSH) in NEC plants in response to viral infection suggest that in addition to SA, GSH may also contribute to the elevated viral resistance of NEC. Furthermore, we found that NEC displays an enhanced resistance not only to viral pathogens but also to bacterial infections and abiotic oxidative stress induced by paraquat treatments. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Plant Expression of Trans-Encapsidated Chimeric Viral Vaccines with Animal RNA Replicons: An Update.

In this protocol, we outline how to produce a chimeric viral vaccine in a biosafety level 1 (BSL1) environment. An animal viral vector RNA encapsidated with tobacco mosaic virus (TMV) coat protein can be fully assembled in planta. Agrobacterium cultures containing each component are inoculated together into tobacco leaves and the self-assembled hybrid chimeric viral vaccine is harvested 4days later and purified with a simple PEG precipitation. The viral RNA delivery vector is derived from the BSL1 insect virus, Flock House virus (FHV), and replicates in human and animal cells but does not spread systemically. A polyethylene glycol purification protocol is also provided to collect and purify these vaccines for immunological tests. In this update, we also provide a protocol for in trans co-inoculation of a modified FHV protein A, which significantly increased the yield of in planta chimeric viral vaccine.

Naked-eye detection of plant viral disease using polymerase chain reaction amplification and DNAzyme.

Plant viral diseases can seriously affect the yield and quality of crops. In this work, a convenient and highly sensitive biosensor for the visual detection of plant viral disease is proposed by the PCR-induced generation of DNAzyme. In the absence of nucleic acid for a target plant virus, the primers prohibited the production of G-quadruplex by forming a hairpin structure. However, PCR amplification occurred and generated a number of specific PCR products with free G-quadruplex sequences at both ends in the presence of the target cDNA. A catalytically active G-quadruplex DNAzyme was formed with the help of K+ and hemin, resulting in the formation of colored products visible to the naked eye and a strong absorbance by the addition of ABTS2- and H2O2. The absorbance and the logarithm of target cDNA concentrations showed a good linear relationship in the range of 10 fM-1.0 nM, with a linear regression equation of A = 0.1402 lg c + 0.3761 (c: fM) and a detection limit of 0.19 fM. This method was successfully applied to the analysis of emerging tobacco mosaic virus (TMV) infections in tobacco leaf samples collected in the field due to its flexibility and convenience, indicating a potential application for the early detection of plant viral disease.

Phylo-geographic analysis of whitefly on the basis of mitochondrial cytochrome oxidase 1 gene

Abstract Bemisia tabaci is a species complex that causes damage to its broad range of plant hosts through serious feeding. It transmits plant viruses of different groups to important agricultural crops. Some important cash crops of Pakistan are sugar cane, rice, tobacco and seed oil. It shows high genetic variability and is differentiated as races or biotypes. Biotypes are, biotype Q, biotype B, biotype B2, biotype M, biotype L, biotype A, biotype H, biotype C, biotype K, biotype N, biotype R, biotype E, biotype P, biotype J, biotype S, biotype AN. Although the current report based on the Bayesian study of mitochondrial cytohrome oxidase gene1 (CO1) DNA sequences has classified the different populations of whiteflies into twelve genetic groups which are Mediterranean, Sub-Saharan Africa silverleafing, Indian Ocean, Asia II, Asia I, Australia, New World, Italy, China, Sub-Saharan Africa non-silverleafing, Mediterranean/Asia Minor/Africa and Uganda sweet potato. Begomoviruses is largest group of viruses transmitted by B. tabaci and cause major diseases of crops such as tomato and chili leaf curl disease, cassava mosaic disease; yellow mosaic disease of legumes and cotton leaf curl disease. The main objective of current study is to inculpate knowledge regarding genetic diversity of whitefly in cotton fields across Pakistan via analysis of partial DNA sequence of mitochondrial gene Cytochrom Oxidase I (mtCO1).

Effects of Xylo-oligosaccharides on soybean growth and mosaic virus disease resistance

Effects of Xylo-oligosaccharides on soybean growth and mosaic virus disease resistance

TEMPO-conjugated tobacco mosaic virus as a magnetic resonance imaging contrast agent for detection of superoxide production in the inflamed liver.

Superoxide, an anionic dioxygen molecule, plays a crucial role in redox regulation within the body but is implicated in various pathological conditions when produced excessively. Efforts to develop superoxide detection strategies have led to the exploration of organic-based contrast agents for magnetic resonance imaging (MRI). This study compares the effectiveness of two such agents, nTMV-TEMPO and kTMV-TEMPO, for detecting superoxide in a mouse liver model with lipopolysaccharide (LPS)-induced inflammation. The study demonstrates that kTMV-TEMPO, with a strategically positioned lysine residue for TEMPO attachment, outperforms nTMV-TEMPO as an MRI contrast agent. The enhanced sensitivity of kTMV-TEMPO is attributed to its more exposed TEMPO attachment site, facilitating stronger interactions with water protons and superoxide radicals. EPR kinetics experiments confirm kTMV-TEMPO's faster oxidation and reduction rates, making it a promising sensor for superoxide in inflamed liver tissue. In vivo experiments using healthy and LPS-induced inflamed mice reveal that reduced kTMV-TEMPO remains MRI-inactive in healthy mice but becomes MRI-active in inflamed livers. The contrast enhancement in inflamed livers is substantial, validating the potential of kTMV-TEMPO for detecting superoxide in vivo. This research underscores the importance of optimizing contrast agents for in vivo imaging applications. The enhanced sensitivity and biocompatibility of kTMV-TEMPO make it a promising candidate for further studies in the realm of medical imaging, particularly in the context of monitoring oxidative stress-related diseases.

First report of prunus necrotic ringspot virus infecting rose (Rosa spp.) in Lebanon

Summary Prunus necrotic ringspot virus (PNRSV) was detected in several rose plants showing symptoms of rose mosaic disease (RMD) in Beqaa valley, Lebanon. PNRSV was found in 29 plants by molecular and serological analyses, while other viruses associated with RMD were absent. Although PNRSV is known to have a wide host range, the present paper reports the first occurrence of PNRSV on rose plants in Lebanon.

Characterization of Blackgram Germplasm [Vigna mungo (L.) Hepper] for Yield and Resistance to Yellow Mosaic Disease

Characterization of Blackgram Germplasm [Vigna mungo (L.) Hepper] for Yield and Resistance to Yellow Mosaic Disease

Natural field diagnosis and molecular confirmation of fungal and bacterial watermelon pathogens in Bangladesh: A case study from the Natore and Sylhet districts.

The study investigated watermelon diseases characterized by contrasting climatic conditions in the Sylhet and Natore Districts of Bangladesh. Sylhet experiences lower temperatures and high rainfall, while Natore has higher temperatures and low rainfall. In these survey regions, 40 watermelon fields were selected, and 10 diseases were observed, including 4 fungal, 3 bacterial, 2 water mold, and 1 viral disease. The observed diseases were Anthracnose, Cercospora leaf spot, Fusarium wilt, Gummy stem blight, Downy mildew, Phytophthora fruit rot, Bacterial fruit blotch, Angular leaf spot, Yellow vine, and Watermelon mosaic disease. Molecular analysis was done in the Plant Pathology Lab at Sher-e-Bangla Agricultural University using the specific primers for fungal (ITS1/ITS4) and bacterial (27F/1492R) DNA regions and identified nine pathogen species, excluding the causal organism of the viral disease. The identified pathogens included Colletrotrichum orbiculare, Cercospora citrullina, Fusarium oxysporum, Stagonosporopsis cucurbitacearum, Pseudoperonospora cubensis, Phytophthora capsici, Acidovorax citrulli, Pseudomonas syringae, and Serratia marcescens. The sequencing of the identified pathogens revealed high homology (98.91-99.71%) with known sequences in the GenBank database. Phylogenetic analysis showed six clusters for fungal and water mold pathogen isolates and three for bacterial isolates where the percentages of replicate trees were 100% in all the cases. Among the identified diseases, the highest disease occurrence was caused by Fusarium wilt (47.5%) followed by Gummy stem blight (41.5%) in the Sylhet region and Angular leaf spot (37.5%) followed by Yellow vine (33%) in the Natore area. Fusarium wilt also has a high disease intensity, demonstrating its devastating impact on yield. This study highlights the influence of environmental conditions on disease incidence and underscores the need for tailored management strategies. These findings provide a foundation for developing targeted disease management practices for sustainable watermelon cultivation in Bangladesh.

Geographical distribution of emerging cacao mosaic disease caused by cacao mild mosaic virus (Badnavirus tesellotheobromae) in Indonesia

AbstractIndonesia is the third largest cocoa producer in the world with annual export value of more than 1.2 million USD. However, cacao production in Indonesia has decreased by approximately 50% in the last decade due to socioeconomic issues and the high prevalence of pests and diseases. Cacao mosaic disease caused by cacao mild mosaic virus (Badnavirus teselotheobromae, CMMV) is currently emerging in Indonesia. This study aims to map the distribution of CMMV in cacao‐growing areas in Indonesia. Samples were collected in 2021–2023 in Java, Sumatera, Bali, and Sulawesi, which represent major cacao‐growing areas in Indonesia. We successfully detected CMMV from all samples, indicating CMMV is already distributed widely in Indonesia. Sequencing data suggests the Indonesian isolates have a common ancestor with American isolates. These findings provide new information for the quarantine board, government, and industry to arrange the policy to control the emerging CMMV.

Unveiling mungbean yellow mosaic virus: molecular insights and infectivity validation in mung bean (Vigna radiata) via infectious clones.

Yellow mosaic disease (YMD) with typical symptoms of alternating bright yellow to green patches associated with stunting, downward cupping, and wrinkling has been observed in mung bean on agricultural farms in Coimbatore, Tamil Nadu, India. PCR using gene-specific primers indicated the presence of the yellow mosaic virus in symptomatic plants. Rolling circle amplification (RCA) followed by restriction digestion detected ~2.7 kb of DNA-A and DNA-B, allowing the identification of a bipartite genome. The full-length genome sequences were deposited in NCBI GenBank with the accession numbers MK317961 (DNA-A) and MK317962 (DNA-B). Sequence analysis of DNA-A showed the highest sequence identity of 98.39% to the DNA-A of mungbean yellow mosaic virus (MYMV)-Vigna radiata (MW736047), while DNA-B exhibited the highest level of identity (98.21%) to the MYMV-Vigna aconitifolia isolate (DQ865203) reported from Tamil Nadu. Recombinant analysis revealed distinct evidence of recombinant breakpoints of DNA-A within the region encoding the open reading frame (ORF) AC2 (transcription activation protein), with the major parent identified as MYMV-PA1 (KC9111717) and the potential minor parent as MYMV-Namakkal (DQ86520.1). Interestingly, a recombination event in the common region (CR) of DNA-B, which encodes the nuclear shuttle protein and the movement protein, was detected. MYMIV-M120 (FM202447) and MYMV-Vigna (AJ132574) were identified as the event's major and minor parents, respectively. This large variation in DNA-B led us to suspect a recombination in DNA-B. Dimeric MYMV infectious clones were constructed, and the infectivity was confirmed through agroinoculation. In future prospects, unless relying on screening using whiteflies, breeders and plant pathologists can readily use this agroinoculation procedure to identify resistant and susceptible cultivars to YMD.

Myricetin derivatives containing the benzoxazinone moiety discovered as potential anti-tobacco mosaic virus agents

A series of myricetin derivatives containing benzoxazinone were designed and synthesized. The structures of all compounds were characterized by NMR and HRMS. The structure of Y4 had been confirmed by single-crystal X-ray diffraction analysis. The test results of EC50 values of tobacco mosaic virus (TMV) suggested that Y8 had the best curative and protective effects, with EC50 values of 236.8, 206.0 μg/mL, respectively, which were higher than that of ningnanmycin (372.4, 360.6 μg/mL). Microscale thermophoresis (MST) experiments demonstrated that Y8 possessed a strong binding affinity for tobacco mosaic virus coat protein (TMV-CP), with a dissociation constant (Kd) value of 0.045 μM, which was superior to the ningnanmycin (0.700 μM). The findings of molecular docking studies revealed that Y8 interacted with multiple amino acid residues of TMV-CP through the formation of non-covalent bonds, which had an effect on the self-assembly of TMV particles. The malondialdehyde (MDA) and superoxide dismutase assay (SOD) content assays also fully verified that Y8 could stimulate the plant immune system and enhance disease resistance by reducing MDA content and increasing SOD content. In summary, myricetin derivatives containing benzoxazinone could be considered to further research and development as novel antiviral agents.

Phytosanitary state of open-field vegetable crop agroecosystems of the genus Solanum, Raphanus, Brassica in the central part of the Right-Bank Forest-Steppe of Ukraine

Goal. Phytosanitary assessment and determination of pest and disease prevalence and development in open-field vegetable crop plantings of the genus Solanum (tomato, pepper, eggplant), genus Raphanus (radish, oilseed radish, common radish, black radish, daikon), and genus Brassica (cabbage, cauliflower, broccoli) in the Central Part of the Right-Bank Forest-Steppe Region of Ukraine.
 Methods. The research was conducted using established entomological, phytopathological, and horticultural methods. From 2008 to 2022, the population, distribution, and development of pests and phytopathogens were assessed in households and small farms within the Cherkasy region of Ukraine.
 Results. Among the dominant pest species in the agroecosystems of vegetable crops from the genus Solanum, insects accounted for 80% (8 species), followed by mites at 10% (1 species), and slugs at 10% (1 species). In agroecosystems of Brassicaceae crops, insects caused significant damage, constituting 94% (16 species) of the total pest structure, along with naked snails (1 species). The area of infestation in tomato, sweet pepper, and eggplant crops by phytophagous insects ranged from 13% to 98%, with plant damage ranging from 14% to 65%. Common spider mites accounted for 26%. Exceedances of the Economic Pest Threshold (EPT) were observed, such as Leptinotarsa decemlineata Say at 2.6 times, Gryllotalpa gryllotalpa L., Trialeurodes vaporariorum Wstw., Agrotis segetum Denis & Schiff., and Lacanobia oleracea at 2.2 times, Agriotes spp. larvae at 1.4 times, and Tetranychus urticae Koch. at 1.9 times the threshold levels. The highest area of infestation in Brassicaceae crops was found for Eurydema ventralis (46.7%), Pieris brassicae (42.4%), Agrotis segetum Denis & Schiff. (41.6%), Phyllotreta crusiferae and Phyllotreta undulate (37.6—37.8%), and Brevicoryne brassicae (26.6%). Exceedances of the EPT were recorded at 1.1—2.5 times for these pests. In the structure of the phytopathogenic complex of vegetable crop agroecosystems, fungi were dominant, accounting for an average of 49—58%. Viral pathogens had the smallest share, approximately 6—8%, causing mosaic diseases. Bacterial and oomycete agents occupied an intermediate position in the pathogenic complex structure. Nevertheless, their negative impact on plant health could be significant.
 Conclusions. In the Cherkasy region, which encompasses the central part of the Right-Bank Forest-Steppe of Ukraine, approximately 75% of surveyed vegetable crop plantings, including tomatoes, peppers, eggplants, radishes, oilseed radishes, common radishes, black radishes, daikons, cabbages, cauliflowers, and broccolis, exhibit high pest infestations exceeding the EPT thresholds, indicating an ecologically hazardous phytosanitary state. In these agroecosystems, insects dominated, representing 80% and 94% of the pest structure in Solanum and Brassicaceae crops, respectively. Additionally, significant damage was attributed to naked snails (Kailie gliemeži) and, in the case of Solanum crops, mites (Tetranychus urticae Koch.). EPT exceedances ranged from 1.1 to 2.5 times, depending on the pest species. Fungi, causing mycoses, dominated the phytopathogenic complex structure, ranging from 14% to 40% (max 88—90%). The prevalence of diseases varied from 21% to 38%, with disease development rates ranging from 21% to 33%. Among the identified phytopathogens, five species are among the world’s most dangerous: Pseudomonas syringae and Xanthomonas campestris (bacteria), Botrytis cinerea and Fusarium oxysporum (fungi), and Phytophthora infestans (oomycete), which require strict control of their populations.

Resistant Gene Analogue Marker(S) Screening against Yellow Mosaic Disease in Mungbean [Vigna radiata (L.) Wilczek

During Rabi 2021–2022, 100 genotypes of mungbean were tested for resistance to yellow mosaic disease in the field using the disease grading system. Out of the 100 mungbean genotypes, 49 were resistant to the yellow mosaic disease, 22 as Moderately resistant, 11 as Moderately susceptible, 3 as susceptible, and 15 were highly susceptible. The sequenced virus shares 98.94% similarity with the whole coding sequence of the MYMIV-Mb02 coat protein (AV1) gene from the mungbean yellow mosaic India virus strain, accession number GQ387502.1., as per the results of the BLAST program. As a result, the variation was designated mungbean yellow mosaic India virus isolates NAU-RJ coat protein gene segment and assigned the accession number ON622515.1. The current study examined Six resistant (40 C, NMS-21-01, NMS-21-06, NMS-21-22, NMS-21-49, NMS-21-95) and six highly susceptible (GM 4, NMS-21-23, NMS-21-24, NMS-21-40, NMS-21-68, NMS-21-69). In order to identify the six susceptible and six resistant mungbean genotypes, nine pairs of RGA primers were employed. Five pairs of RGA primers were successfully amplified in all resistant genotypes as a consequence, but not in all highly susceptible genotypes. The results of this study suggest that five pairs of RGA markers can effectively distinguish between the genotypes of mungbean that are highly susceptible and resistant. The long-lasting YMV resistance of these RGA markers makes them useful for mapping resistance genes and marker validation studies.

Wheat stripe mosaic virus from Brazil and South Africa evolved as distinct subpopulations with low genetic variability

AbstractWheat stripe mosaic virus (WhSMV) is the causal agent of soilborne wheat mosaic disease (SBWMD) in Brazil, which is a serious threat to wheat production in the southern part of the country. WhSMV also occurs in Paraguay and South Africa. The virus is soilborne, transmitted by Polymyxa graminis, and management strategies are mainly based on genetic resistance. Variation in the reaction (type and severity of symptoms) of cultivars has been reported depending on the region and/or year of cultivation, leading wheat breeding programmes to test their materials in several locations, which increases costs and is time‐consuming. One hypothesis is that this variation in symptoms is a result of the genetic variability of WhSMV. We assessed the genetic variability and population structure of WhSMV infecting wheat in Brazil and South Africa. In field experiments conducted in different locations in southern Brazil, a consistent reproducibility of symptoms was observed in a set of cultivars, and molecular analysis showed a low degree of genetic variability of the Brazilian viral population. The hypothesis that the variation in SBWMD symptoms in Brazil is due to genetic variability of the virus was thus rejected. Comparison of the Brazilian and South African WhSMV isolates indicated that they comprise distinct subpopulations and that the Brazilian subpopulation is more variable than the South African subpopulation. The lower genetic variability of the South African subpopulation suggests genetic stability or a recent emergence of WhSMV in that region.