BUSCADOR RECOLECTA

Environmental conditions can affect viral accumulation, virulence and adaptation, which have implications in the disease outcomes and efficiency of control measures. Concurrently, mixed viral infections are relevant in plants, being their epidemiology shaped by within-host virus-virus interactions. However, the extent in which the combined effect of variations in abiotic components of the plant ecological niche and the prevalence of mixed infections affect the evolutionary dynamics of viral populations is not well understood. Here, we explore the interplay between ecological and evolutionary factors during viral infections and show that isolates of two strains of Pepino mosaic potexvirus coexisted in tomato plants in a temperature-dependent continuum between neutral and antagonistic interactions. After a long-term infection, the mutational analysis of the evolved viral genomes revealed strain-specific single-nucleotide polymorphisms that were modulated by the interaction between the type of infection and temperature. These results suggest that the temperature is an ecological driver of virus-virus interactions, with an effect on the genetic diversity of individual viruses that are co-infecting an individual host. This research provides insights into the effect that changes in host growth temperatures might have on the evolutionary dynamics of viral populations in mixed infections.

© 2021 by the authors., Viral infections on cucurbit plants cause substantial quality and yield losses on their crops. The diseased plants can often be infected by multiple viruses, and their epidemiology may depend, in addition to the agro-ecological management practices, on the combination of these viral infections. Watermelon mosaic virus (WMV) is one of the most prevalent viruses in cucurbit crops, and Moroccan watermelon mosaic virus (MWMV) emerged as a related species that threatens these crops. The occurrence of WMV and MWMV was monitored in a total of 196 apical-leaf samples of watermelon and pumpkin plants that displayed mosaic symptoms. The samples were collected from 49 fields in three major cucurbit-producing areas in Spain (Castilla La-Mancha, Alicante, and Murcia) for three consecutive (2018–2020) seasons. A molecular hybridization dot-blot method revealed that WMV was mainly (53%) found in both cultivated plants, with an unadvertised occurrence of MWMV. To determine the extent of cultivated plant species and mixed infections on viral dynamics, two infectious cDNA clones were constructed from a WMV isolate (MeWM7), and an MWMV isolate (ZuM10). Based on the full-length genomes, both isolates were grouped phylogenetically with the Emergent and European clades, respectively. Five-cucurbit plant species were infected steadily with either WMV or MWMV cDNA clones, showing variations on symptom expressions. Furthermore, the viral load varied depending on the plant species and infection type. In single infections, the WMV isolate showed a higher viral load than the MWMV isolate in melon and pumpkin, and MWMV only showed higher viral load than the WMV isolate in zucchini plants. However, in mixed infections, the viral load of the WMV isolate was greater than MWMV isolate in melon, watermelon and zucchini, whereas MWMV isolate was markedly reduced in zucchini. These results suggest that the impaired distribution of MWMV in cucurbit crops may be due to the cultivated plant species, in addition to the high prevalence of WMV., This work was supported by the Spanish research grant; AGL2017-89550-R from the
Agencia Estatal de Investigación (AEI) and FEDER (EU) funds. M.P.R. was supported by funding
of the Ministry of sciences, innovation and universities (MICINN, Spain) within a PhD programme
grant (PRE2018-083915)., Peer reviewed

Aphid borne viruses are responsible for major plant diseases, we monitored for three consecutive (2018-2020) seasons, the presence of aphid-borne viruses from a total of 292 samples of watermelon and squash that showed yellowing symptoms. The samples were collected from three major cucurbit-producing areas (Castilla La-Mancha, Alicante and Murcia) in Spain. We found that cucurbit aphid-borne yellow virus (CABYV) was the most common virus found (29%) in the plants from both crops. Likewise, except for squash samples from Castilla La-Mancha and Alicante, watermelon mosaic virus (WMV) was also found (23%) with a relatively high frequency in watermelon plants, while the occurrences of PRSV and ZYMV were low (<3%), and even CMV was undetected in both plant species. Additionally, two CABYV cDNA infectious clones (CABYV LP-63 and CABYV-MEC 12.1) were constructed for further characterization, with the LP63 isolate causing more severe symptoms and showing higher RNA accumulation than MEC12.1 in five cucurbits plant species., Funding: AGL2017-89550-R from the Agencia Estatal de Investigación (AEI) and FEDER (EU) funds., Peer reviewed

Environmental conditions can affect viral accumulation, virulence and adaptation, which have implications in the disease outcomes and efficiency of control measures. Concurrently, mixed viral infections are relevant in plants, being their epidemiology shaped by within-host virus–virus interactions. However, the extent in which the combined effect of variations in abiotic components of the plant ecological niche and the prevalence of mixed infections affect the evolutionary dynamics of viral populations is not well understood. Here, we explore the interplay between ecological and evolutionary factors during viral infections and show that isolates of two strains of Pepino mosaic potexvirus coexisted in tomato plants in a temperature-dependent continuum between neutral and antagonistic interactions. After a long-term infection, the mutational analysis of the evolved viral genomes revealed strain-specific single-nucleotide polymorphisms that were modulated by the interaction between the type of infection and temperature. These results suggest that the temperature is an ecological driver of virus-virus interactions, with an effect on the genetic diversity of individual viruses that are co-infecting an individual host. This research provides insights into the effect that changes in host growth temperatures might have on the evolutionary dynamics of viral populations in mixed infections., We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)., CA was supported by the Ministry of Economy, Industry and Competitiveness (MINECO, Spain) within a PhD programme grant (FPU16/02569). This work was supported by the Agencia Estatal de Investigación-FEDER grants AGL2014-59556-R and AGL2017-89550-R to PG and PID2019-103998GB-I00 to SFE. JS has been partially funded by the CERCA Programme of the Generalitat de Catalunya, MINECO grant MTM2015-71509-C2-1-R, Agencia Estatal de Investigación grant RTI2018-098322-B-I00, and by a Ramón y Cajal contract (RYC-2017-22243)., Peer reviewed

Aphid-borne viruses are responsible for major cucurbit diseases and hamper the sustainability of crop production. Systematic monitoring can reveal the occurrence and distribution of these viruses, in addition to unadvertised viruses, facilitating the control of diseases. For three consecutive (2018–2020) seasons, the presence of aphid-borne viruses was monitored from a total of 292 samples of watermelon and squash plants that showed yellowing symptoms in three major cucurbit-producing areas (Castilla La-Mancha, Alicante, and Murcia) in Spain. We observed that cucurbit aphid-borne yellows virus (CABYV) was the most common virus found (29%) in the plants from both crops. Likewise, except for squash samples from Castilla La-Mancha and Alicante, watermelon mosaic virus (WMV) was also found (23%) with a relatively high frequency. Furthermore, we observed the exacerbation of bright yellowing symptoms in watermelon plants that was often accompanied by considerable fruit abortion. CABYV was the only causative agent for this new yellowing disease, and two infectious cDNA clones (one from watermelon, CABYV-LP63, and another from melon, CABYV-MEC12.1) were constructed to further compare and characterize this CABYV disease. Based on the full-length genome, both isolates were grouped phylogenetically together within the Mediterranean clade. However, the Koch's postulates tests were only successfully completed for the LP63 isolate, which also showed several amino acid changes and two potential recombination events, as compared to MEC12.1. Remarkably, the LP63 isolate caused more severe symptoms and showed higher RNA accumulation than MEC12.1 in five cucurbit plant species. These results suggest that a novel CABYV variant that causes severe yellowing symptoms may be causing outbreaks in cucurbit crops, M.P.R. was supported by funding of the Ministry of sciences, innovation and universities (MICINN, Spain) within a PhD programme grant (PRE2018-083915). This work was supported by the Spanish research grant; AGL2017-89550-R from the Agencia Estatal de Investigación (AEI) and FEDER (EU) funds, Peer reviewed

Multiple viral infection is an important issue in health and agriculture with strong impacts on society and the economy. Several investigations have dealt with the population dynamics of viruses with different dynamic properties, focusing on strain competition during multiple infections and the effects on viruses’ hosts. Recent interest has been on how multiple infections respond to abiotic factors such as temperature (T). This is especially important in the case of plant pathogens, whose dynamics could be affected significantly by global warming. However, few mathematical models incorporate the effect of T on parasite fitness, especially in mixed infections. Here, we investigate simple mathematical models incorporating thermal reaction norms (TRNs), which allow for quantitative analysis. A logistic model is considered for single infections, which is extended to a Lotka-Volterra competition model for mixed infections. The dynamics of these two models are investigated, focusing on the roles of T-dependent replication and competitive interactions in both transient and asymptotic dynamics. We determine the scenarios of co-existence and competitive exclusion, which are separated by a transcritical bifurcation. To illustrate the applicability of these models, we ran single- and mixed-infection experiments in plants growing at 20º C and 30º C using two strains of the plant RNA virus Pepino mosaic virus. Using a macroevolutionary algorithm, we fitted the models to the data by estimating the TRNs for both strains in single infections. Then, we used these TRNs to feed the mixed-infection model estimating the strength of competition. We found an asymmetrical pattern in which each strain dominated at different T values due to differences in their TRNs. We also identified that T can modify competition interference greatly for both isolates. The models proposed here can be useful for investigating the outcomes of multiple-infection dynamics under abiotic changes and have implications for the understanding of viral responses to global warming., J.S. has been partially funded by the CERCA Program of the Generalitat de Catalunya, by the Ministry of Economy, Industry and Competitiveness (MINECO) grant MTM2015-71509-C2-1-R, by Agencia Estatal de Investigación (AEI) grant RTI2018-098322-B-I00, and by a Ramón y Cajal contract (RYC-2017-22243). C.A. was funded by the MINECO within a PhD program grant (FPU16/02569). This work was also supported by the AEI-FEDER grants AGL2014-59556-R and AGL2017-89550-R to P.G. and PID2019-103998GB-I00 to S.F.E., Peer reviewed

The effectiveness of pest and disease management in crops relies on knowledge about their presence and distribution in crop-producing areas. Aphids and whiteflies are among the main threats to vegetable crops since these hemipterans feed on plants, causing severe damage, and are also able to transmit a large number of devastating plant viral diseases. In particular, the widespread occurrence of aphid-transmitted viruses in cucurbit crops, along with the lack of effective control measures, makes surveillance programs and virus epidemiology necessary for providing sound advice and further integration into the management strategies that can ensure sustainable food production. This review describes the current presence and distribution of aphid-transmitted viruses in cucurbits in Spain, providing valuable epidemiological information, including symptom expressions of virus-infected plants for further surveillance and viral detection. We also provide an overview of the current measures for virus infection prevention and control strategies in cucurbits and indicate the need for further research and innovative strategies against aphid pests and their associated viral diseases., This research was funded by the Spanish research grant (AGL2017-89550-R) from MICINN and EU FEDER funds. CDMR was supported by funding from the Fundación Séneca within a PhD programme grant (SENECA 21417/FPI/20)., Peer reviewed

Understanding the emergence and prevalence of viral diseases in crops requires the systematic epidemiological monitoring of viruses, as well as the analysis of how ecological and evolutionary processes combine to shape viral population dynamics. Here, we extensively monitored the occurrence of six aphid-transmitted viruses in melon and zucchini crops in Spain for 10 consecutive cropping seasons between 2011 and 2020. The most prevalent viruses were cucurbit aphid-borne yellows virus (CABYV) and watermelon mosaic virus (WMV), found in 31 and 26% of samples with yellowing and mosaic symptoms. Other viruses, such as zucchini yellow mosaic virus, cucumber mosaic virus, Moroccan watermelon mosaic virus, and papaya ring spot virus, were detected less frequently (<3%) and mostly in mixed infections. Notably, our statistical analysis showed a significant association between CABYV and WMV in melon and zucchini hosts, suggesting that mixed infections might be influencing the evolutionary epidemiology of these viral diseases. We then carried out a comprehensive genetic characterization of the full-length genome sequences from CABYV and WMV isolates by using the Pacific Biosciences single-molecule real-time (PacBio) high-throughput technology to assess the genetic variation and structure of their populations. Our results showed that the CABYV population displayed seven codons under positive selection, and although most isolates clustered in the Mediterranean clade, a subsequent analysis of molecular variance revealed a significant, fine-scale temporal structure, which was in part explained by the level of the variance between isolates from single and mixed infections. In contrast, the WMV population genetic analysis showed that most of the isolates grouped into the Emergent clade, with no genetic differentiation and under purifying selection. These results underlie the epidemiological relevance of mixed infections for CABYV and provide a link between genetic diversity and CABYV dynamics at the whole-genome level, Ministry of Science and Innovation and EU FEDER
Grant/Award Number: AGL2014-59556-R
Grant/Award Number: AGL2017-89550-R
Ministry of Science and Innovation
Grant/Award Number: PRE2018-083915, Peer reviewed

Cucurbit aphid-borne yellows virus (CABYV) and watermelon mosaic virus (WMV) are major plant pathogens that cause severe epidemics in cucurbit crops. While there has been an increasing interest in molecular epidemiological studies on both viruses at regional scales, their phylodynamic analysis by using the temporal data at global scale remains unexplored. In this study, we implemented the Nextstrain phylodynamic approach to comprehensively examine the coat protein gene and full-length genome sequences of the CABYV and WMV worldwide populations. Our analyses reconstructed a robust phylogeny of CABYV and confirmed the occurrence of isolates grouped into three clusters (Asian, Mediterranean, and Recombinant). Nextstrain analysis suggested that CABYV epidemics likely originated in Southeast Asia in fourteenth century, while the Mediterranean population emerged in Spain in seventeenth century. We also found a high divergence between Asian and Mediterranean isolates, with low genetic diversity and scarce evidence of selection, as reflected by the lack of gene flow. Moreover, the hierarchical analysis of molecular variance revealed a significant differentiation between CABYV populations grouped by geographical location and plant host. Additionally, the global phylogenetic reconstruction of the WMV population confirmed a clear differentiation among isolates, which grouped into two clusters (classical and emergent), and Nextstrain analysis suggested that WMV epidemics were most probably originated in USA during the sixteenth century. The initial WMV population diverged in the eighteenth century, with the origin of the emergent population in the nineteenth century. Our analysis confirmed that WMV population has a polyphyletic origin, defining an extensive genetic diversity. Overall, this work provides insights into the CABYV and WMV origin and evolutionary dynamics, gaining an understanding of the global spread of both viral diseases. Additionally, the integration of all spatio-temporal CABYV and WMV data, along with their genome sequence data by open access (https://github.com/PiR92) and the Nextstrain approach, provides a valuable tool for compiling and sharing current knowledge of these viral diseases in cucurbit crops, We thank that this work was supported by the Spanish research grants (AGL2017-89550-R) from MICINN and EU FEDER funds, and also that M.P.R. was supported by funding of the Ministry of Economy, Industry and Competitiveness (MINECO, Spain) within a PhD programme grant (PRE2018-083915), Peer reviewed