Identification and molecular characterization of Bean yellow mosaic virus infecting French bean in Himachal Pradesh

Metatranscriptome and small RNA sequencing revealed a mixed infection of newly identified bymovirus and bean yellow mosaic virus on peas

Peas (Pisum sativum L.) are widely cultivated in temperate regions and are susceptible hosts for various viruses across different families. The discovery and identification of new viruses in peas has significant implications for field disease management. Here, we identified a mixed infection of two viruses from field-collected peas exhibiting virus-like symptoms using metatranscriptome and small RNA sequencing techniques. Upon identification, one of the viruses was determined to be a newly isolated and discovered bymovirus from peas, named "pea bymovirus 1 (PBV1)". The other was identified as a novel variant of bean yellow mosaic virus (BYMV-HZ1). Subsequently, mechanical inoculation and RT-PCR assays confirmed that both viruses could be inoculated back onto peas and tobaccos, showing mixed infection by PBV1 and BYMV-HZ1. To our knowledge, this is the first isolation of a bymovirus from pea and the first documented case of mixed infection of peas by PBV1 and BYMV-HZ1 in China.

Antiviral activity of chitosan nanoparticles for controlling plant-infecting viruses

Chitosan nanoparticles (ChiNPs) are a potentially effective means for controlling numerous plant diseases. This study firstly describes the antiviral capabilities of ChiNPs to control plant viral diseases compared to its bulk form. Bean yellow mosaic virus (BYMV) was used as a model plant virus affecting faba bean plants and many other legumes. The antiviral effectiveness of ChiNPs and chitosan were evaluated as a curative application method, using six dosage rates (50, 100, 200, 250, 300 and 400 mg/L). Results indicated that ChiNPs curatively applied 48 h post virus inoculation entirely inhibit the disease infectivity and viral accumulation content at 300 mg/L and 400 mg/L. The virus titre was greatly alleviated within the plant tissues by 7.71% up to100% depending on ChiNP dosage rates. However, chitosan used in its bulk-based material form revealed a relatively low to an intermediate reduction in virus infectivity by 6.67% up to 48.86%. Interestingly, ChiNPs affect the virus particle’s integrity by producing defective and incomplete BYMV viral particles, defeating their replication and accumulation content within the plant tissues. Simultaneously, ChiNP applications were appreciably shown to promote the pathogenesis-related (PR-1) gene and other defence-related factors. The mRNA of the PR-1 gene was markedly accumulated in treated plants, reaching its maximum at 400 mg/L with 16.22-fold relative expression change over the untreated control. Further, the total phenol dynamic curve was remarkably promoted for 30 days in response to ChiNP application, as compared to the untreated control. Our results provide the first report that chitosan-based nanomaterials have a superior effect in controlling plant viruses as an antiviral curing agent, suggesting that they may feasibly be involved in viral disease management strategies under field conditions without serious health concerns and environmental costs.

PHYLOGENETIC ANALYSIS OF BEAN YELLOW MOSAIC VIRUS ISOLATES FROM GLADIOLI IN UKRAINE

Bean yellow mosaic virus (BYMV) is the one of most prevalent and harmful viruses infecting gladiolus plants worldwide. The aim of the study was to perform phylogenetic analysis of two Ukrainian BYMV isolates from gladioli grown in different regions of Ukraine and determine phylogenetic relationships of the isolates to other BYMVs. Visual diagnostics, enzyme-linked immunosorbent assay in DAS-ELISA modification, total RNA extraction, RT-PCR, phylogenetic analysis and statistical data analysis were used in this research. The results of the studies showed that gladioli of variety Pamyat’ (Poltava region, 2018) and var. Galyna Zelenobirska (Kyiv region, 2020) with symptoms of chlorotic stripes and mosaics on the leaves, flower color breaks are infected by BYMV. Fragments of the CP gene sequence of Ukrainian gladiolus isolates of bean yellow mosaic virus, named GlMP-18 (MK416160) and BYMV-Gl-SV-20 (MZ286966) were sequenced and deposited to the NCBI GenBank. Nucleotide sequences of these isolates corresponding to 578 nt of the coat protein gene (CP) located at the position 8727–9305 of the viral genome and amino acid sequences were compared with 40 known BYMV isolates/strains. Phylogenetic analysis demonstrated that GlMP-18 and BYMV-Gl-SV-20 have identity of nucleotide sequence 100% and amino acid sequence 100% with each other. Both Ukrainian isolates clustered with the Monocot group. The identity of the СР gene sequences of the two gladiolus isolates GlMP-18 and BYMV-Gl-SV-20 from geographically remote regions of the country and in different years of selection indicates a common origin of isolates and probable their distribution of planting material.

Silver nanoparticles as a viricidal agent to inhibit plant-infecting viruses and disrupt their acquisition and transmission by their aphid vector

Silver nanoparticles (AgNPs) are a potentially effective tool for preventing viral plant diseases. This study was carried out to evaluate the effectiveness of AgNPs for managing bean yellow mosaic virus (BYMV) disease in faba bean plants from the plant-virus-vector interaction side. AgNPs were evaluated as foliar protective and curative agents. In addition, the effect of AgNPs on virus acquisition and transmission by its vector aphid was investigated. The results indicated that AgNPs exhibited curative viricidal activity and were able to inactivate BYMV when applied 48 hours after virus inoculation. The occurrence of disease was prevented using an AgNP concentration as low as 100 mg L^-1, whereas virus infection was completely inhibited when plants were preventatively treated with AgNPs at a concentration of to 200 mg L^-1 24 h before virus inoculation. AgNPs proved to be highly bio-reactive, binding to viral particles and suppressing their replication and accumulation within plant tissues. Moreover, AgNPs, at all concentrations tested, were found to upregulate the pathogenesis-related gene PR-1 and induce the production of defense-related oxidizing enzymes in treated plants. Exposure of aphids to AgNPs-treated plants before virus acquisition reduced BYMV acquisition and transmission efficiency by 40.65 to 100% at 24 h post-application, depending on the AgNP dosage. At 10 days after treatment, virus acquisition was reduced by 36.82% and 79.64% upon exposure to AgNPs at a concentration of 250 and 300 mg L-¹, respectively. These results suggest that AgNPs have curative viricidal activity due to targeting the virus coat protein and affecting virus-vector interactions. Accordingly, AgNPs may contribute to alleviating the natural disease and virus transmission under field conditions. This is the first report on the activity of nanomaterials against plant virus acquisition and transmission by insects.

Biological and molecular characterization of bean bushy stunt virus, a novel bipartite begomovirus infecting common bean in northwestern Argentina

Common bean plants (Phaseolus vulgaris L.) showing different virus-like symptoms were collected in northwestern Argentina. Dot-blot hybridization tests showed that the begomoviruses bean golden mosaic virus and tomato yellow vein streak virus were the most prevalent, but they also revealed the presence of unknown begomoviruses. The complete genome sequence of one of these unknown begomoviruses was determined. Sequence analysis showed that the virus is a typical New World begomovirus, for which the name "bean bushy stunt virus" (BBSV) is proposed. Biological assays based on biolistic inoculations showed that BBSV induced leaf roll and stunting symptoms similar to those observed in the field-collected common bean sample.

Sequence analysis of six full-length bean yellow mosaic virus genomes reveals phylogenetic diversity in India strains, suggesting subdivision of phylogenetic group-IV

We report the complete genome sequence of five bean yellow mosaic virus (BYMV) isolates (CK-GL1, CK-GL3, CK-GL4, CK-GL5 and Vfaba2) that share 74.6-98.9% (nucleotide) and 81.5-99.1% (amino acid) identity with globally available BYMV sequences. Phylogenetic analysis clustered them specifically in BYMV phylogenetic group-IV within the existing nine groups. The CK-GL1, CK-GL2, CK-GL4 and CK-GL5 isolates formed a discrete cluster within group-IV. The present study suggests subdivision of group-IV into subgroup-IVa and IVb. Moreover, infectivity assays using in vitro RNA transcripts from subgroup-IVa (CK-GL3 isolate) and IVb (CK-GL1 isolate) showed distinct biological differences between the isolates supporting subdivision.