Papaya Leaf Curl Research Articles

Molecular Identification and Genetic Diversity Analysis of Papaya Leaf Curl China Virus Infecting Ageratum conyzoides.

Papaya leaf curl China virus (PaLCuCNV) is a damaging plant pathogen causing substantial losses to crop. The complete genomes of three PaLCuCNV isolates from Ageratum conyzoides were obtained and combined with the 68 reference isolates in GenBank for comprehensive genetic diversity analyses using specialized computational tools. Sequence alignment revealed nucleotide sequence similarity ranging from 85.3% to 99.9% among 71 PaLCuCNV isolates. Employing phylogenetic analysis, 71 PaLCuCNV sequences were clustered into five groups, with no significant correlation observed between genetic differentiation and either host species or geographical origin. Additionally, 13 recombination events across all PaLCuCNV isolates were identified. Genetic diversity analysis indicated the ongoing expansion and evolution of PaLCuCNV populations, supported by a neutral model. Moreover, significant genetic differentiation was observed among distinct viral populations, primarily attributed to genetic drift. Overall, our findings provide valuable insights into the detection, genetic variation, and evolutionary dynamics of PaLCuCNV.

Molecular characterization of bipartite begomovirus associated with papaya Leaf curl disease in Chhattisgarh, India

Molecular characterization of bipartite begomovirus associated with papaya Leaf curl disease in Chhattisgarh, India

Virus Infected Papaya Plants Differentially affects Oxidative Stress and Survival in Caenorhabditis elegans

Carica papaya (papaya) leaves has significant nutraceutical properties. However, it is speculated that papaya leaf curl virus (PaLCuV) and papaya ring spot virus (PRSV) can severely affect the therapeutic properties and alter the overall nutraceutical potential of papaya leaves. Therefore, we evaluated the bioactivity of the virus infected papaya leaves extract (PLE) compared to healthy PLE in C. elegans. Viruses infection were confirmed by visual inspection and PCR based detection. Anatomical changes and elemental analysis were analyzed through SEM-EDS. PLE were tested for life span extension and ROS scavenging activity on C. elegans. Infected leaves displayed typical symptoms of curling, distortion and anatomical analysis revealed closed and less number of stomata. Healthy PLE extended (24%) the life span of C. elegans with no significant change in ROS generation while in PaLCuV and PRSV infected PLE, were observed to have significant reduction in the mean life span of 15.4% and 17% with 1.2-fold and 1.9-fold increase in ROS generation.

In-silico prediction and validation of Carica papaya protein domains interaction with the Papaya leaf curl virus and associated betasatellite encoded protein

Begomovirus, the first-largest genus of plant viruses in family Geminiviridae, is a persistent menace to plants that causes millions of dollars’ worth of damage in a variety of vital crops around the world. One of the most important tropical fruit crops is Carica papaya, which has a wealth of pharmacological and bioactive components that are commonly used to treat a wide range of human illnesses, is infected by divergent begomovirus species. Here, we report the interacting regions of the one of the begomovirus species i.e. Papaya Leaf Curl Virus (PaLCuV and Papaya leaf betasatellite (PaLCuB) protein with papaya plant protein by using computational approaches. This includes primary sequence recognition, secondary structural assessment, 3D modelling, energy minimization, binding site prediction, protein–protein interaction, and interface analysis. Our results showed that papaya plant protein such as S-adenosyl methionine synthetase (SAMS), Proliferating cell nuclear antigen (PCNA), Cyclin-dependent kinases regulatory subunit 1 (CDK1), Adenosine kinase (ADK), and Calmodulin (CaM), an encoded protein of C. papaya, are involved in host–virus interaction. However, we find the best domain-level interactions based on the structural and interface analysis of the SAMS-CP, PCNA-Rep, CDK1-Rep, ADK-REn, CaM-PreCP, and PCNA-βC1 proteins of PaLCuV–PaLCuB. In this study, we attempted to understand the sequence–structure relationship and mode of the virus–host binding complex, which was verified and validated with integrative in silico approaches. Using several bioinformatics tools, our study has provided novel insights into the papaya protein–begomovirus protein binding mechanism. Thus, we anticipate that our findings from this study will be useful for the development of new therapeutic agents against the pathogen, paving the way for researchers to better control this destructive plant virus. This is the first in-silico investigation that combined the prediction and structural validation and interface analysis of the interaction between PaLCuV–PaLCuB and papaya proteins.

Genome organization of satellite DNA beta molecule associated with Mungbean yellow mosaic India virus Gujarat, India

Recent advancements in genomics have unveiled fascinating insights into the intricate world of plant pathogens. The discovery of an intriguing association between the DNA beta and MYMIV-[IN:Ana: CpMBKA25:04], a strain containing 1367 base pairs of nucleotides, has sparked a wave of scientific curiosity. Through sequence identity matrix analysis, it was revealed that this strain shares a striking 96% similarity with the Potato apical leaf curl virus, closely followed by the Tomato leaf curl beta satellite virus [Accession No. AY230138] at 95.3%. In contrast, its relationship with the beta satellite Bhendi yellow vein beta satellite [Accession No. AJ308425] stood at a comparative 45.7% when compared against seventeen other DNA beta isolates infecting various crops. Noteworthy features of the beta satellite sequences include a distinctive putative stem-loop structure TAATATT/AC in the common region and a recurring GCTACGC repeat sequence. An A-rich region spanning from nucleotides 910 to 1120 further adds to the genetic complexity of this novel strain. Intriguingly, an analysis of the amino acid sequence unveiled additional residues V, C, and N at the carboxyl end of the βC1 protein, setting it apart from its counterparts. The identity matrix analysis established a 95.9% similarity between βC1 and the beta satellite associated with Tomato leaf curl Karnataka virus and Potato apical leaf curl virus, phylogenetic analysis placed the beta satellite linked with MYMIV-[IN:Ana: CpMBKA25:04] in a distinct category within the Papaya leaf curl virus family, shedding light on its unique evolutionary lineage and biological significance in the realm of plant virology.

Enhancing Papaya Leaf Disease Detection with CNN and Transfer Learning Fusion for Precise Disease Diagnosis

Papaya cultivation plays a vital role in global agriculture, providing a crucial source of nutrition and economic stability. However, the threat of diseases poses a significant challenge to papaya plant health. To address this challenge, we proposed an innovative approach for enhancing the detection of papaya leaf diseases using Convolutional Neural Networks (CNNs) and transfer learning fusion. Our proposed framework leverages the strengths of CNNs, known for their ability to extract intricate features from images, and the transfer learning approach combines these techniques to create a robust and efficient model for accurate papaya leaf disease diagnosis. Transfer learning approach with two pre-trained models: VGG-16 and ResNet-50 are taken to detect papaya leaf diseases. The training process involves utilizing a pre-trained model and fine-tuning it on a specific papaya leaf disease dataset. For experimentation, five different classes of papaya leaves such as Fresh Papaya Leaf, Papaya Black Spot, Papaya Leaf Curl, Papaya Ringspot, and Powdery Mildew of Papaya are considered. Experimental results demonstrate the effectiveness of our proposed approach in accurately identifying and classifying various papaya leaf diseases. The proposed model has received an accuracy of 99.79% using ResetNet-50 followed by CNN whose accuracy was 99.42% and VGG-16, whose accuracy was 98.25%. This fusion approach aims to create a robust and efficient model capable of distinguishing subtle patterns indicative of various papaya leaf diseases. This method not only improves the efficiency of disease detection but also demonstrates the adaptability of the model to various disease patterns. Our study contributes to the advancement of automated papaya leaf disease detection, providing a reliable and precise tool for early diagnosis. Overall, our approach offers a promising solution for improving papaya cultivation and ensuring a sustainable future for global agriculture.

In silico identification of papaya genome-encoded microRNAs to target begomovirus genes in papaya leaf curl disease.

Papaya leaf curl disease (PaLCuD) is widespread and classified in the genus begomovirus (Geminiviridae), disseminated by the vector whitefly Bemisia tabaci. RNA interference (RNAi)-based antiviral innate immunity stands as a pivotal defense mechanism and biological process in limiting viral genomes to manage plant diseases. The current study aims to identify and analyze Carica Papaya locus-derived capa-microRNAs with predicted potential for targeting divergent begomovirus species-encoded mRNAs using a 'four integrative in silico algorithms' approach. This research aims to experimentally activate the RNAi catalytic pathway using in silico-predicted endogenous capa-miRNAs and create papaya varieties capable of assessing potential resistance against begomovirus species and monitoring antiviral capabilities. This study identified 48 predicted papaya locus-derived candidates from 23 miRNA families, which were further investigated for targeting begomovirus genes. Premised all the four algorithms combined, capa-miR5021 was the most anticipated miRNA followed by capa-miR482, capa-miR5658, capa-miR530b, capa-miR3441.2, and capa-miR414 'effective' papaya locus-derived candidate capa-miRNA and respected putative binding sites for targets at the consensus nucleotide position. It was predicted to bind and target mostly to AC1 gene of the complementary strand and the AV1 gene of the virion strand of different begomovirus isolates, which were associated with replication-associated protein and encapsidation, respectively, during PaLCuD. These miRNAs were also found targeting betaC1 gene of betasatellite which were associated with retardation in leaf growth and developmental abnormalities with severe symptoms during begomovirus infection. To validate target prediction accuracy, we created an integrated Circos plot for comprehensive visualization of host-virus interaction. In silico-predicted papaya genome-wide miRNA-mediated begomovirus target gene regulatory network corroborated interactions that permit in vivo analysis, which could provide biological material and valuable evidence, leading to the development of begomovirus-resistant papaya plants. The integrative nature of our research positions it at the forefront of efforts to ensure the sustainable cultivation of papaya, particularly in the face of evolving pathogenic threats. As we move forward, the knowledge gained from this study provides a solid foundation for continued exploration and innovation in the field of papaya virology, and to the best of our knowledge, this study represents a groundbreaking endeavor, undertaken for the first time in the context of PaLCuD research.

Important Diseases of Papaya in Andhra Pradesh

Papaya (Carica papaya L.) stands as one of the most delectable fruits globally, flourishing primarily in tropical and sub-tropical climates. Despite its widespread cultivation, the potential yield and marketability of papaya are continually threatened by various diseases. The susceptibility of papaya to an array of fungal, viral, and bacterial infections, such as Phytophthora root rot, anthracnose, powdery mildew, stem end rot, black spot disease, papaya ring spot, and papaya leaf curl, has impeded commercial production on a global scale. Among these diseases, Papaya ring spot virus, Phytophthora foot rot and anthracnose, incited by Colletotrichum gloeosporioides Penz. emerging as the most important problems those directly affecting the economic yield. This article delves into a comprehensive exploration of the symptoms, epidemiology, and control measures associated with the predominant papaya diseases prevalent in India. Furthermore, it elucidates effective strategies and control measures that can be employed to mitigate the impact of these diseases, offering valuable insights to farmers, researchers, and stakeholders involved in papaya cultivation.

First report of Tomato leaf curl Karnataka virus causing papaya leaf curl disease in India

First report of <i>Tomato leaf curl Karnataka virus</i> causing papaya leaf curl disease in India

Efficacy of Selected Biocontrol Agents in Controlling Papaya Leaf Curl Disease

Efficacy of Selected Biocontrol Agents in Controlling Papaya Leaf Curl Disease

First Report of Passiflora latent virus in Passion fruit (Passiflora edulis) in China.

Passion fruit (Passilora edulis, family Passifloraceae.) is an economically important fruit crop in many tropical and subtropical regions worldwide. It is widely planting in southern China, and in greenhouses throughout the country. In Mar 2022, symptoms of a viral-like infection were observed on the leaves of passion fruit plants in a 3-hectare greenhouse complex in Hohhot, China. Chlorotic lesions were observed on leaves of two vines of passion fruit and symptomatic leaves developed chlorotic spots, followed by systemic leaf chlorosis and necrosis. Dark ringed spots emerged on the surface of matured fruits (Figure 1). To confirm infectivity, mechanical transmission of the virus was performed by grinding leaves from two symptomatic passion fruit vines in 0.1M phosphate buffer pH 7, and the resulting two samples were each used to rub-inoculate carborundum-dusted leaves of three healthy passion fruit seedlings. Newly emerging leaves of inoculated plants developed mild mosaic symptoms 30-days after inoculation. Three samples from each of the two original symptomatic plants and two samples from each inoculated seedling tested positive using a Passiflora latent virus (PLV) ELISA Kit (Creative Diagnostics, USA). To further confirm the virus identity, total RNA from leaf samples from one of the original greenhouse symptomatic plants and one of the inoculated seedlings were extracted using an TaKaRa MiniBEST Viral RNA Extraction Kit (Takara, Japan). The two RNA samples were subjected to reverse transcription-polymerase chain reaction (RT-PCR) tests with virus specific primers PLV-F (5'-ACACAAAACTGCGTGTTGGA-3') and PLV-R (5'-CAAGACCCACCTACCTCAGTGTG-3') (Cho et al., 2020). RT-PCR products of the expected 571 bp were obtained from both the original greenhouse sample and inoculated seedling. Amplicons were cloned into the pGEM-T Easy Vector, and two clones per sample were Sanger sequenced bidirectionally (Sangon Biotech, China), and the sequence of one clone from one of the original symptomatic sample was uploaded to NCBI (GenBank OP320922.1). This accession had 98% nucleotide sequence identity with a PLV isolate from Korea (GenBank: LC556232.1). RNA extracts from two asymptomatic samples tested negative for PLV with both ELISA and RT-PCR tests. We also tested the original symptomatic sample for common occurring passion fruit viruses, including passion fruit woodiness virus (PWV), cucumber mosaic virus (CMV), east asian passiflora virus (EAPV), telosma mosaic virus (TeMV), papaya leaf curl Guangdong virus (PaLCuGdV), and the RT-PCR results were negative for those viruses. However, based on the systemic leaf chlorosis and necrosis symptoms, we cannot preclude a mixed infestation of other viruses. PLV affects fruit quality and has high potential to reduce market value. To our knowledge, this is the first report of PLV in China, which could provide a reference basis to PLV identification, prevention and control. Acknowledgments This research was carried out with the support of Inner Mongolia Normal University High-level Talents Scientific Research Startup Project (Grant no. 2020YJRC010). Supplementary material Figure 1. Mottle, leaf distortion, puckering symptoms on old leaf (A), mild puckering symptom on young leaf (B), and ring-striped spots symptoms on fruit (C) of the PLV infected passion fruit plant in China.

First Report of Passiflora Latent Virus Infecting Passion Fruit (Passiflora edulis) in South Korea.

Passion fruit (Passiflora edulis) viral diseases caused by papaya leaf curl Guangdong virus, cucumber mosaic virus, East Asian Passiflora virus, and euphorbia leaf curl virus have been reported in South Korea (Joa et al. 2018; Kim et al. 2018). In June 2021, virus-like symptoms, e.g., mosaic pattern, curling, chlorosis, and deformation, were observed on leaves and fruits of greenhouse-grown P. edulis in Iksan, South Korea, with disease incidence greater than 2% (300 plants: 8 symptomatic plants and 292 asymptomatic plants). Total RNA was extracted from a pooled sample of symptomatic leaves of an individual P. edulis plant using the RNeasy Plant Mini Kit (Qiagen, Germany), and a transcriptome library was generated using the TruSeq Stranded Total RNA LT Sample Prep Kit (Illumina, San Diego, CA). Next-Generation Sequencing (NGS) was performed using the Illumina NovaSeq 6000 system (Macrogen Inc., Korea). De novo assembly of the resulting 121,154,740 reads was performed using Trinity (Grabherr et al. 2011). A total of 70,895 contigs was assembled (>200 bp) and annotated against the NCBI viral genome database using BLASTn (ver. 2.12.0). One 827-nt contig was annotated as milk vetch dwarf virus (MVDV), a member of the genus Nanovirus in the family Nanoviridae (Bangladesh isolate, acc. no. LC094159, 96.0% nucleotide identity), and the other 3,639-nt contig corresponded to Passiflora latent virus (PLV), a member of the genus Carlavirus in the family Betaflexiviridae (Israel isolate, acc. no. DQ455582, 90.0% nucleotide identity). For further confirmation, total RNA was isolated from symptomatic leaves of the same P. edulis used for NGS analysis using a viral gene spin DNA/RNA extraction kit (iNtRON Biotechnology, Seongnam, Korea), and reverse transcription polymerase chain reaction (RT-PCR) was performed using specific primers: PLV-F/R (5'-GTGCCCACCGAACATGTTACCTC-3'/5'-CCATGCACTTGGAATGCTTACCC-3') targeting the coat protein region of PLV, MVDV-M-F/R (5'-CTAGTCAGCCATCCAATGGTG-3'/5'-GTGCAGGGTTTGATTGTCTGC-3') targeting the movement protein region, and MVDV-S-F/R (5'-GGATTTTAATACGCGTGGACGATC-3'/5'-AACGGCTATAAGTCACTCCGTAC-3') targeting the coat protein region of MVDV. An expected PCR product of 518 bp corresponding to PLV was amplified, while MVDV was not detected. The amplicon was directly sequenced, and its nucleotide sequence was deposited in GenBank (acc. no. OK274270). A BLASTn analysis showed that the nucleotide sequence of the PCR product shared 93.0% and 96.2% identity with PLV isolates from Israel (MH379331) and Germany (MT723990), respectively. In addition, six passion fruit leaves and two fruit samples with PLV-like symptoms were collected from a total of eight plants grown in the greenhouse in Iksan for RT-PCR analysis, and six samples tested positive for PLV. However, PLV was not detected in one leaf and one fruit among all samples. Mechanical sap inoculation was conducted using extracts of systemic leaves as inoculum on P. edulis and the indicator plants Chenopodium quinoa, Nicotiana benthamiana, N. glutinosa, and N. tabacum. In P. edulis, vein chlorosis and yellowing on systemic leaves were observed 20 days post inoculation (dpi). Necrotic local lesions were observed on inoculated leaves of N. benthamiana and N. glutinosa 15 dpi, and PLV infection was confirmed by RT-PCR assay in symptomatic leaf tissue. This study aimed to determine whether commercially grown passion fruit in the southern part of South Korea could be infected with and potentially spread PLV. Whereas PLV was asymptomatic in persimmon (Diospyros kaki) in South Korea, no pathogenicity testing in passion fruit was reported (Cho et al. 2021). Here, we have shown the natural infection of passion fruit with PLV in South Korea for the first time and associated infection with obvious symptoms. This suggests a need to evaluate potential losses in passion fruit and the selection of healthy propagation material.

An Insight into Emerging Begomoviruses and their Satellite Complex causing Papaya Leaf Curl Disease.

Papaya leaf curl disease (PaLCD) was primarily detected in India and causes major economic damage to agriculture crops grown globally, seriously threatening food security. Begomoviruses are communicated by the vector Bemisia tabaci, and their transmission efficiency and persistence in the vector are the highest, exhibiting the widest host range due to adaptation and evolution. Symptoms induced during PaLCD include leaf curl, leaf yellowing, interveinal chlorosis, and reduced fruit quality and yield. Consequently, plants have evolved several multi-layered defense mechanisms to resist Begomovirus infection and distribution. Subsequently, Begomovirus genomes organise circular ssDNA of size ~2.5-2.7 kb of overlapping viral transcripts and carry six-seven ORFs encoding multifunctional proteins, which are precisely evolved by the viruses to maintain the genome-constraint and develop complex but integrated interactions with a variety of host components to expand and facilitate successful infection cycles, i.e., suppression of host defense strategies. Geographical distribution is continuing to increase due to the advent and evolution of new Begomoviruses, and sweep to new regions is a future scenario. This review summarizes the current information on the biological functions of papaya-infecting Begomoviruses and their encoded proteins in transmission through vectors and modulating host-mediated responses, which may improve our understanding of how to challenge these significant plant viruses by revealing new information on the development of antiviral approaches against Begomoviruses associated with PaLCD.

Identification of Novel Begomoviruses Associated with Leaf Curl Disease of Papaya (Carica papaya L.) in India

Papaya (Carica papaya L.) is one of the most important fruit crops grown in tropical and subtropical regions of the world. Papaya leaf curl disease is one of the greatest concerns next to Papaya ring spot disease for India and the world. A survey was conducted during the year 2019 to 2021 for assessing the leaf curl disease incidence in five major papaya-growing districts of Karnataka State, India. The incidence ranged from 10 to 21 percent, with plants expressing typical begomovirus symptoms. Thirty-two virus-infected papaya samples (PLC-1 to PLC-32), collected from different farmer’s fields, gave positive amplification for begomovirus detection. Based on the partial genome analysis, 13 representative papaya leaf curl isolates were selected for complete genome amplification by rolling circle DNA amplification (RCA). The RCA products were cloned, sequenced and analyzed. Based on the analysis and strain classification criteria for begomoviruses, five isolates (PLC-2, 3, 9, 11 and 18) were considered variants of Chilli leaf curl virus (ChiLCV). Isolate PLC-22 is considered a strain of ChiLCV, with 93.5% nt identity sharing. Similarly, isolate PLC-28 is considered a strain of Croton yellow vine mosaic virus (CYVMV), and isolates PLC-25 and PLC-31 were considered as strains of Papaya leaf curl virus (PaLCuV). Among the remaining four isolates, three (PLC-1, PLC-4 and PLC-7) share more than 91% nt identity among them and less than 91% nt identity with all other reported begomovirus isolates. Hence, they are considered to be isolates of the novel begomovirus, and the name Papaya leaf curl Bagalkote virus [India:Karnataka:Bagalkote:Papaya:2021] is proposed. One isolate (PLC-32) is also found to be distinct from all other begomovirus isolates, including the isolates in the current study also considered to be novel begomovirus, for which we propose the name Papaya leaf curl Haveri virus [India:Karnataka:Haveri:Papaya:2021]. The putative recombination analysis of all 13 papaya isolates showed that a major part of the viral genome was likely descended from the begomoviruses reported previously. This is the first report on the diversity and a distribution of the begomoviruses infecting papaya in Karnataka, India. The current investigation results revealed five major papaya-infecting begomoviruses (PaLCuBKV, ChiLCV, PaLCuV, CYVMV and PaLCuHV) in the sampled regions.

Mixed infection of a new begomovirus, Jatropha leaf curl Guntur virus and recombinant/chimeric jatropha leaf curl Gujarat virus in Jatropha gossypiifolia.

The Jatropha gossypiifolia plant showing the severe leaf curl symptoms grown in the borders of chilli fields in Guntur, Andhra Pradesh, India was collected. The infection of begomovirus was detected using the degenerate primers followed by rolling circle amplification (RCA). The RCA products digested with KpnI and EcoRI showing the unit length of the begomovirus genome were cloned in pUC19 and sequenced to obtain the complete begomoviral genome. The sequence information of DNA-A of the two clones GuWC10 contained 2794 nt (MZ217773) and an incomplete genome GuWC3 with 2337 nt (MZ217772). The BLAST analysis of GuWC3 and GuWC10 sequence showed 85·57% identity with jatropha leaf curl Gujarat virus (JLCGV) and 82·68% identity with croton yellow vein mosaic virus (CroYVMV), respectively. The sequence analysis also showed that the GuWC10 clone had a 177 bp recombinant/chimeric sequence of JLCGV while the other region containing 2611 bp showed 92·63% identity with papaya leaf curl virus (PaLCuV/PK). However, the global alignment of the GuWC10 sequence showed a maximum of 80·60% identity with croton yellow vein virus (CroYVV) (FN645902), CroYVMV (JN817516) and PaLCuV/PK (KY978407). The second clone GuWC3 although shorter in length had recombinant sequences of JLCGV, jatropha leaf curl virus (JLCuV/ND) and okra enation leaf curl virus (OELCuV). The nucleotide sequence identity among the GuWC10 and GuWC3 was 71·9%. The phylogenetic analysis placed both the viral strains in the same clade located between PaLCuV/PK and JLCuV clades. According to the ICTV species demarcation criteria of 91% DNA-A sequence identity, the present isolate was considered as a new species of begomovirus and the name Jatropha leaf curl Guntur virus was proposed. This is the first report of a new begomovirus species infecting J. gossypiifolia and the study also reports a mixed infection of Jatropha leaf curl Guntur virus with a recombinant/chimeric JLCGV in the host J. gossypiifolia. Present study suggests the role of weed Jatropha in harbouring begomoviruses and probable source for viral recombination.

Association of papaya leaf curl virus and DNA satellite molecules with leaf curl disease of sunhemp (Crotalaria juncea L.) in India

Association of papaya leaf curl virus and DNA satellite molecules with leaf curl disease of sunhemp (Crotalaria juncea L.) in India

Evolutionary Dynamics of Begomoviruses and Its Satellites Infecting Papaya in India.

The genus Begomovirus represents a group of multipartite viruses that significantly damage many agricultural crops, including papaya, and influence overall production. Papaya leaf curl disease (PaLCD) caused by the complex begomovirus species has several important implications and substantial losses in papaya production in many developing countries, including India. The increase in the number of begomovirus species poses a continuous threat to the overall production of papaya. Here, we attempted to map the genomic variation, mutation, evolution rate, and recombination to know the disease complexity and successful adaptation of PaLCD in India. For this, we retrieved 44 DNA-A and 26 betasatellite sequences from GenBank reported from India. An uneven distribution of evolutionary divergence has been observed using the maximum-likelihood algorithm across the branch length. Although there were phylogenetic differences, we found high rates of nucleotide substitution mutation in both viral and sub-viral genome datasets. We demonstrated frequent recombination of begomovirus species, with a maximum in intra-species recombinants. Furthermore, our results showed a high degree of genetic variability, demographic selection, and mean substitution rate acting on the population, supporting the emergence of a diverse and purifying selection of viruses and associated betasatellites. Moreover, variation in the genetic composition of all begomovirus datasets revealed a predominance of nucleotide diversity principally driven by mutation, which might further accelerate the advent of new strains and species and their adaption to various hosts with unique pathogenicity. Therefore, the finding of genetic variation and selection emphases on factors that contribute to the universal spread and evolution of Begomovirus and this unanticipated diversity may also provide guidelines toward future evolutionary trend analyses and the development of wide-ranging disease control strategies for begomoviruses associated with PaLCD.

Papaya Leaf Curl Virus (PaLCuV) Infection on Papaya (Carica papaya L.) Plants Alters Anatomical and Physiological Properties and Reduces Bioactive Components.

Papaya leaves are used frequently for curing scores of ailments. The medicinal properties of papaya leaves are due to presence of certain bioactive/pharmacological compounds. However, the papaya leaf curl virus (PaLCuV), a geminivirus, is a major threat to papaya cultivation globally. During the present investigation, we observed that PaLCuV infection significantly altered the anatomy, physiology, and bioactive properties of papaya leaves. As compared to healthy leaves, the PaLCuV-infected leaves were found to have reduced stomatal density (76.83%), stomatal conductance (78.34%), photosynthesis rate (74.87%), water use efficiency (82.51%), chlorophyll (72.88%), carotenoid (46.63%), osmolality (48.55%), and soluble sugars (70.37%). We also found lower enzymatic activity (superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT)—56.88%, 85.27%, and 74.49%, respectively). It was found that the size of guard cells (50%), transpiration rate (45.05%), intercellular CO2 concentration (47.81%), anthocyanin (27.47%), proline content (74.17%), malondialdehyde (MDA) (106.65%), and electrolyte leakage (75.38%) was elevated in PaLCuV-infected leaves. The chlorophyll fluorescence analysis showed that the infected plant leaves had a significantly lower value of maximal quantum yield of photosystem II (PSII (Fv/Fm), photochemical quantum yield of photosystem I (PSI (Y(I)), and effective quantum yield of PSII (Y(II)). However, in non-photochemical quenching mechanisms, the proportion of energy dissipated in heat form (Y(NPQ)) was found to be significantly higher. We also tested the bioactivity of infected and healthy papaya leaf extracts on a Caenorhabditis elegans (C. elegans) model system. It was found that the crude extract of papaya leaves significantly enhanced the life span of C. elegans (29.7%) in comparison to virus-infected leaves (18.4%) on application of 100 µg/mL dose of the crude extract. Our research indicates that the PaLCuV-infected leaves not only had anatomical and physiological losses, but that pharmacological potential was also significantly decreased.

First report of Euphorbia leaf curl virus and papaya leaf curl Guangdong virus on passion fruit in mainland China

First report of Euphorbia leaf curl virus and papaya leaf curl Guangdong virus on passion fruit in mainland China

Natural occurrence of mesta yellow vein mosaic virus and DNA-satellites in ornamental sunflower (Helianthus spp.) in Pakistan.

Weeds and ornamental plants serve as a reservoir for geminiviruses and contribute to their dissemination, genome recombination and/or satellite capture. Ornamental sunflower (Helianthus spp.) plants exhibiting mild leaf curl symptoms were subjected to begomovirus and DNA-satellites isolation. The full-length genome of the isolated begomovirus clone (Od1-A) showed 96.8% nucleotide (nt) sequence identity with mesta yellow vein mosaic virus (MeYVMV; accession no. FR772081) whereas, alphasatellite (Od1-a) and betasatellite (Od1-b) clones showed their highest nt sequence identities at 97.4% and 98.2% with ageratum enation alphasatellite (AEA; accession no. FR772085) and papaya leaf curl betasatellite (PaLCuB; accession. no. LN878112), respectively. The evolutionary relationships, average evolutionary divergence and the recombination events were also inferred. The MeYVMV exhibited 9.5% average evolutionary divergence and its CP and Rep had 9.3% and 12.2%, concomitantly; the alphasatellite and the betasatellite had 8.3% and 5.2%, respectively. The nt substitution rates (site-1 year−1) were found to be 6.983 × 10-04 and 5.702 × 10-05 in the CP and Rep of MeYVMV, respectively. The dN/dS ratio and the Tajima D value of MeYVMV CP demonstrated its possible role in host switching. The absolute quantification of the begomovirus demonstrated that mild symptoms might have a correlation with low virus titer. This is the first identification of MeYVMV and associated DNA-satellites from ornamental sunflower in Pakistan. The role of sequence divergence, recombination and importance of MeYVMV along with DNA-satellites in extending its host range is discussed.