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One of the most important and widespread corn/maize virus diseases is maize dwarf mosaic (MDM), which can be induced by sugarcane mosaic virus (SCMV). This study explores a machine learning analysis of five-band multispectral imagery collected via an unmanned aerial system (UAS) during the 2021 and 2022 seasons for SCMV disease detection in corn fields. The three primary objectives are to (i) determine the spectral bands and vegetation indices that are most important or correlated with SCMV infection in corn, (ii) compare spectral signatures of mock-inoculated and SCMV-inoculated plants, and (iii) compare the performance of four machine learning algorithms, including ridge regression, support vector machine (SVM), random forest, and XGBoost, in predicting SCMV during early and late stages in corn. On average, SCMV-inoculated plants had higher reflectance values for blue, green, red, and red-edge bands and lower reflectance for near-infrared as compared to mock-inoculated samples. Across both years, the XGBoost regression model performed best for predicting disease incidence percentage (R2 = 0.29, RMSE = 29.26), and SVM classification performed best for the binary prediction of SCMV-inoculated vs. mock-inoculated samples (72.9% accuracy). Generally, model performances appeared to increase as the season progressed into August and September. According to Shapley additive explanations (SHAP analysis) of the top performing models, the simplified canopy chlorophyll content index (SCCCI) and saturation index (SI) were the vegetation indices that consistently had the strongest impacts on model behavior for SCMV disease regression and classification prediction. The findings of this study demonstrate the potential for the development of UAS image-based tools for farmers, aiming to facilitate the precise identification and mapping of SCMV infection in corn. [ABSTRACT FROM AUTHOR]

Cryopreservation for sugarcane (Saccharum spp. hybrids) germplasm conservation is well established. Virus elimination using droplet-vitrification (D-V) and cryo- or osmo-therapy has only been recently reported for sugarcane mosaic virus (SCMV). In this study, exposing large (3 mm) in vitro shoot tips of cultivars N12, N19, N58, and NCo376 infected with sugarcane yellow leaf virus (SCYLV) and NCo376 co-infected with SCMV and SCYLV were tested for virus elimination using both of the above-mentioned techniques. Cryo-therapy involved the exposure of infected in vitro shoot tips to the D-V protocol followed by recording recovery and virus-free shoot tips 16 wk after treatment. Osmo-therapy, consisting of the same treatment as cryo-therapy without immersion in liquid nitrogen (LN), was included for comparative purposes. Cryo-therapy resulted in 100% of the recovered shoots being SCYLV-free in cultivars N19, N58, and NCo376 and 83% in N12 when compared with untreated material. Osmo-therapy showed 58% (N12), 91% (N19 and N58), and 100% (NCo376) of shoots being clear of SCYLV when compared with untreated in vitro control plants (0 to 8%). Both techniques reduced the regrowth levels of treated shoot tips (22 to 57% recovery) when compared with untreated controls (92 to 97%). A novel finding of the study was that NCo376 co-infected with SCMV and SCYLV showed 100% virus-free recovered shoots after cryo-therapy and 92 to 100% of healthy shoots after osmo-therapy, compared with controls, which had 17 to 42% virus-free shoots. Plants from all cultivars that were re-tested 4 mo after hardening maintained their virus-free status. The described techniques for virus eradication offer a promising solution for the provision of clean vegetative planting propagules and safer germplasm exchange. [ABSTRACT FROM AUTHOR]

Copyright of Acta Agronomica Sinica is the property of Crop Science Society of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

MicroRNAs (miRNAs) play an essential regulatory role in plant-virus interaction. However, few studies have focused on the roles of miRNAs and their targets after sugarcane mosaic virus (SCMV) infection in sugarcane. To address this issue, we conducted small RNA (sRNA) and degradome sequencing on two contrasting sugarcanes (SCMV-resistant ‘Fuoguo1’ [FG1] and susceptible ‘Badila’) infected by SCMV at five time points. A total of 1,578 miRNAs were profiled from 30 sRNA libraries, comprising 660 known miRNAs and 380 novel miRNAs. Differential expression analysis of miRNAs revealed that most were highly expressed during the SCMV exponential phase in Badila at 18 h postinfection, with expression profiles positively correlated with virus replication dynamics as observed through clustering. Analysis of degradome data indicated a higher number of differential miRNA targets in Badila compared to FG1 at 18 h postinfection. Gene ontology (GO) enrichment analysis significantly enriched the stimulus-response pathway, suggesting negative regulatory roles to SCMV resistance. Specifically, miR160 upregulated expression patterns and validated in Badila through quantitative real-time PCR (qRT-PCR) in the early stages of SCMV multiplication. Our research provides new insights into the dynamic response of plant miRNA and virus replication and contributes valuable information on the intricate interplay between miRNAs and SCMV infection dynamics. [Graphic: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Sugarcane mosaic virus (SCMV) (genus, Potyvirus; family, Potyviridae) is widespread, deleterious, and the most damaging pathogen of sugarcane (Saccharum officinarum L. and Saccharum spp.) that causes a substantial barrier to producing high sugarcane earnings. Sugarcane mosaic disease (SCMD) is caused by a single or compound infection of SCMV disseminated by several aphid vectors in a non-persistent manner. SCMV has flexuous filamentous particle of 700–750 nm long, which encapsidated in a positive-sense, single-stranded RNA molecule of 9575 nucleotides. RNA interference (RNAi)-mediated antiviral innate immunity is an evolutionarily conserved key biological process in eukaryotes and has evolved as an antiviral defense system to interfere with viral genomes for controlling infections in plants. The current study aims to analyze sugarcane (Saccharum officinarum L. and Saccharum spp.) locus-derived microRNAs (sof-miRNAs/ssp-miRNAs) with predicted potential for targeting the SCMV +ssRNA-encoded mRNAs, using a predictive approach that involves five algorithms. The ultimate goal of this research is to mobilize the in silico- predicted endogenous sof-miRNAs/ssp-miRNAs to experimentally trigger the catalytic RNAi pathway and generate sugarcane cultivars to evaluate the potential antiviral resistance surveillance ability and capacity for SCMV. Experimentally validated mature sugarcane (S. officinarum, 2n = 8X = 80) and (S. spp., 2n = 100–120) sof-miRNA/ssp-miRNA sequences (n = 28) were downloaded from the miRBase database and aligned with the SCMV genome (KY548506). Among the 28 targeted mature locus-derived sof-miRNAs/ssp-miRNAs evaluated, one sugarcane miRNA homolog, sof-miR159c, was identified to have a predicted miRNA binding site, at nucleotide position 3847 of the SCMV genome targeting CI ORF. To verify the accuracy of the target prediction accuracy and to determine whether the sugarcane sof-miRNA/ssp-miRNA could bind the predicted SCMV mRNA target(s), we constructed an integrated Circos plot. A genome-wide in silico-predicted miRNA-mediated target gene regulatory network was implicated to validate interactions necessary to warrant in vivo analysis. The current work provides valuable computational evidence for the generation of SCMV-resistant sugarcane cultivars.

Given the detrimental effects of excessive reactive oxygen species (ROS) accumulation in plant cells, various antioxidant mechanisms have evolved to maintain cellular redox homeostasis, encompassing both enzymatic components (e.g., catalase, superoxide dismutase) and non‐enzymatic ones. Despite extensive research on the role of antioxidant systems in plant physiology and responses to abiotic stresses, the potential exploitation of antioxidant enzymes by plant viruses to facilitate viral infection remains insufficiently addressed. Herein, we demonstrate that maize catalases (ZmCATs) exhibited up‐regulated enzymatic activities upon sugarcane mosaic virus (SCMV) infection. ZmCATs played crucial roles in SCMV multiplication and infection by catalysing the decomposition of excess cellular H2O2 and promoting the accumulation of viral replication‐related cylindrical inclusion (CI) protein through interaction. Peroxisome‐localized ZmCATs were found to be distributed around SCMV replication vesicles in Nicotiana benthamiana leaves. Additionally, the helper component‐protease (HC‐Pro) of SCMV interacted with ZmCATs and enhanced catalase activities to promote viral accumulation. This study unveils a significant involvement of maize catalases in modulating SCMV multiplication and infection through interaction with two viral factors, thereby enhancing our understanding regarding viral strategies for manipulating host antioxidant mechanisms towards robust viral accumulation. [ABSTRACT FROM AUTHOR]

Sugarcane mosaic virus (SCMV) (genus, Potyvirus; family, Potyviridae) is widespread, deleterious, and the most damaging pathogen of sugarcane (Saccharum officinarum L. and Saccharum spp.) that causes a substantial barrier to producing high sugarcane earnings. Sugarcane mosaic disease (SCMD) is caused by a single or compound infection of SCMV disseminated by several aphid vectors in a non-persistent manner. SCMV has flexuous filamentous particle of 700–750 nm long, which encapsidated in a positive-sense, single-stranded RNA molecule of 9575 nucleotides. RNA interference (RNAi)-mediated antiviral innate immunity is an evolutionarily conserved key biological process in eukaryotes and has evolved as an antiviral defense system to interfere with viral genomes for controlling infections in plants. The current study aims to analyze sugarcane (Saccharum officinarum L. and Saccharum spp.) locus-derived microRNAs (sof-miRNAs/ssp-miRNAs) with predicted potential for targeting the SCMV +ssRNA-encoded mRNAs, using a predictive approach that involves five algorithms. The ultimate goal of this research is to mobilize the in silico- predicted endogenous sof-miRNAs/ssp-miRNAs to experimentally trigger the catalytic RNAi pathway and generate sugarcane cultivars to evaluate the potential antiviral resistance surveillance ability and capacity for SCMV. Experimentally validated mature sugarcane (S. officinarum, 2n = 8X = 80) and (S. spp., 2n = 100–120) sof-miRNA/ssp-miRNA sequences (n = 28) were downloaded from the miRBase database and aligned with the SCMV genome (KY548506). Among the 28 targeted mature locus-derived sof-miRNAs/ssp-miRNAs evaluated, one sugarcane miRNA homolog, sof-miR159c, was identified to have a predicted miRNA binding site, at nucleotide position 3847 of the SCMV genome targeting CI ORF. To verify the accuracy of the target prediction accuracy and to determine whether the sugarcane sof-miRNA/ssp-miRNA could bind the predicted SCMV mRNA target(s), we constructed an integrated Circos plot. A genome-wide in silico-predicted miRNA-mediated target gene regulatory network was implicated to validate interactions necessary to warrant in vivo analysis. The current work provides valuable computational evidence for the generation of SCMV-resistant sugarcane cultivars. [ABSTRACT FROM AUTHOR]

Maize lethal necrosis (MLN) is a viral disease caused by host co-infection by maize chlorotic mottle virus (MCMV) and a potyvirus, such as sugarcane mosaic virus (SCMV). The disease is most effectively managed by growing MLN-resistant varieties. However, the relative importance of MCMV and potyvirus resistance in managing this synergistic disease is poorly characterized. In this study, we evaluated the effects of SCMV and/or MCMV resistance on disease, virus titers, and synergism and explored expression patterns of known potyvirus resistance genes TrxH and ABP1. MLN disease was significantly lower in both the MCMV-resistant and SCMV-resistant inbred lines compared with the susceptible control Oh28. Prior to 14 days postinoculation (dpi), MCMV titers in resistant lines N211 and KS23-6 were more than 100,000-fold lower than found in the susceptible Oh28. However, despite no visible symptoms, titer differences between MCMV-resistant and -susceptible lines were negligible by 14 dpi. In contrast, systemic SCMV titers in the potyvirus-resistant line, Pa405, ranged from 130,000-fold to 2 million-fold lower than susceptible Oh28 as disease progressed. Initial TrxH expression was up to 49,000-fold lower in Oh28 compared with other genotypes, whereas expression of ABP1 was up to 4.5-fold lower. Measures of virus synergy indicate that whereas MCMV resistance is effective in early infection, strong potyvirus resistance is critical for reducing synergist effects of co-infection on MCMV titer. These results emphasize the importance of both potyvirus resistance and MCMV resistance in an effective breeding program for MLN management. [ABSTRACT FROM AUTHOR]

One of the most important and widespread corn/maize virus diseases is maize dwarf mosaic (MDM), which can be induced by sugarcane mosaic virus (SCMV). This study explores a machine learning analysis of five-band multispectral imagery collected via an unmanned aerial system (UAS) during the 2021 and 2022 seasons for SCMV disease detection in corn fields. The three primary objectives are to (i) determine the spectral bands and vegetation indices that are most important or correlated with SCMV infection in corn, (ii) compare spectral signatures of mock-inoculated and SCMV-inoculated plants, and (iii) compare the performance of four machine learning algorithms, including ridge regression, support vector machine (SVM), random forest, and XGBoost, in predicting SCMV during early and late stages in corn. On average, SCMV-inoculated plants had higher reflectance values for blue, green, red, and red-edge bands and lower reflectance for near-infrared as compared to mock-inoculated samples. Across both years, the XGBoost regression model performed best for predicting disease incidence percentage (R2 = 0.29, RMSE = 29.26), and SVM classification performed best for the binary prediction of SCMV-inoculated vs. mock-inoculated samples (72.9% accuracy). Generally, model performances appeared to increase as the season progressed into August and September. According to Shapley additive explanations (SHAP analysis) of the top performing models, the simplified canopy chlorophyll content index (SCCCI) and saturation index (SI) were the vegetation indices that consistently had the strongest impacts on model behavior for SCMV disease regression and classification prediction. The findings of this study demonstrate the potential for the development of UAS image-based tools for farmers, aiming to facilitate the precise identification and mapping of SCMV infection in corn.

Copyright of Acta Agronomica Sinica is the property of Crop Science Society of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Five sugarcane leaf samples exhibiting mosaic symptoms and collected in 1999–2003 in Bangladesh, India, Sri Lanka, Thailand, and Vietnam tested negative in serological assays (ELISA and TBIA) using antiserum to sugarcane mosaic virus (SCMV) and a potyvirus specific monoclonal antibody. In addition, these samples reacted negative in RT-PCR assays with SCMV, sorghum mosaic virus (SrMV), and potyvirus specific primers. Mosaic symptoms were reproduced after mechanical inoculation of sugarcane, maize, and sorghum plants with diseased leaf extracts, but symptoms were less severe than those of SCMV and SrMV. Electron microscopy of partially purified virions from inoculated plants showed flexuous filaments characteristic of the Potyviridae family. The five sugarcane leaf samples tested positive in RT-PCR assays with two primer pairs designed to detect sugarcane streak mosaic virus (SCSMV), and in immunological assays with SCSMV antisera. SCSMV was detected by ELISA with three different antisera and by RT-PCR in 34 leaf samples from 30 cultivars exhibiting mosaic symptoms and originating from six Asian countries (the five mentioned above and Pakistan). The sequences of the RT-PCR amplicons (376 nucleotides) showed 98.5–100% identity with SCSMV isolates from GenBank. The immunological, molecular, and pathogenic characteristics of SCSMV were different from those of SCMV and SrMV. Our results suggested that SCSMV was already widespread in Asia more than two decades ago. Furthermore, immunological variation occurs among SCSMV isolates, which needs to be considered for serological diagnosis of the virus. RT-PCR primers developed in this study proved to be very efficient for detection of SCSMV from different countries. [ABSTRACT FROM AUTHOR]

Spodoptera frugiperda (fall armyworm) is a notorious pest that threatens maize production worldwide. Current control measures involve the use of chemical insecticides and transgenic maize expressing Bacillus thuringiensis (Bt) toxins. Although additional transgenes have confirmed insecticidal activity, limited research has been conducted in maize, at least partially due to the technical difficulty of maize transformation. Here, we describe implementation of a sugarcane mosaic virus (SCMV) vector for rapidly testing the efficacy of both endogenous maize genes and heterologous genes from other organisms for the control of S. frugiperda in maize. Four categories of proteins were tested using the SCMV vector: (i) maize defence signalling proteins: peptide elicitors (Pep1 and Pep3) and jasmonate acid conjugating enzymes (JAR1a and JAR1b); (ii) maize defensive proteins: the previously identified ribosome-inactivating protein (RIP2) and maize proteinase inhibitor (MPI), and two proteins with predicted but unconfirmed anti-insect activities, an antimicrobial peptide (AMP) and a lectin (JAC1); (iii) lectins from other plant species: Allium cepa agglutinin (ACA) and Galanthus nivalis agglutinin (GNA); and (iv) scorpion and spider toxins: peptides from Urodacus yaschenkoi (UyCT3 and UyCT5) and Hadronyche versuta (Hvt). In most cases, S. frugiperda larval growth was reduced by transient SCMV-mediated overexpression of genes encoding these proteins. Additionally, experiments with a subset of the SCMV-expressed genes showed effectiveness against two aphid species, Rhopalosiphum maidis (corn leaf aphid) and Myzus persicae (green peach aphid). Together, these results demonstrate that SCMV vectors are a rapid screening method for testing the efficacy and insecticidal activity of candidate genes in maize.

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ABSTRACT Sugarcane mosaic virus (SCMV) causes mosaic disease in crops such as maize and sugarcane by its vector—an aphid—and is transmitted top-down into the root system. However, understanding of the effects of the aphid-borne virus on root-associated microbes after plant invasion remains limited. The current project investigated maize root-associated (rhizosphere and endosphere) bacterial communities, potential interspecies interaction, and assembly processes in response to SCMV invasion based on 16S rRNA gene amplicon sequencing. SCMV was detected in the roots 9 days after inoculation, and leaf mosaic and chlorosis appeared. The SCMV invasion markedly reduced the α-diversity of endosphere bacteria compared with uninoculated controls (Mock). The connectivity and complexity of the bacterial co-occurrence network in the root endosphere decreased after SCMV invasion, implying that the plant virus may alter root endophyte-microbial interactions. Moreover, a signature that deviates more from stochastic processes was observed in virus-infected plants. Unexpectedly, the rhizosphere bacterial communities were rarely affected by the viral invasion. This study lays the foundation for elucidating the fate of the microbial component of the plant holobiont following aphid-borne virus exposure. IMPORTANCE Biotic (e.g., soil-borne viruses) stress can alter root-associated bacterial communities, essential in maintaining host plant growth and health. However, the regulation of root-associated microorganisms by plant viruses from shoots is still largely unknown. Our results show that plant virus invasion leads to reduced and simpler inter-microbial communication in the maize endosphere. In addition, stochastic processes act on bacterial community assembly in both rhizosphere and endosphere, and bacterial communities in virus-invaded plant endosphere tend to shift toward deterministic processes. Our study highlights the negative effects of plant viruses on root endophytes from the microbial ecology perspective, which may be microbially mediated mechanisms of plant diseases.

Viruses often establish their own infection by altering host metabolism. How viruses co-opt plant metabolism to support their successful infection remains an open question. Here, we used untargeted metabolomics to reveal that lactate accumulates immediately before and after robust sugarcane mosaic virus (SCMV) infection. Induction of lactate-involved anaerobic glycolysis is beneficial to SCMV infection. The enzyme activity and transcriptional levels of lactate dehydrogenase (LDH) were up-regulated by SCMV infection, and LDH is essential for robust SCMV infection. Moreover, LDH relocates in viral replicase complexes (VRCs) by interacting with SCMV-encoded 6K2 protein, a key protein responsible for inducing VRCs. Additionally, lactate could promote SCMV infection by suppressing plant defense responses. Taken together, we have revealed a viral strategy to manipulate host metabolism to support replication compartment but also depress the defense response during the process of infection. [ABSTRACT FROM AUTHOR]

Plant pathogens such as viruses are detrimental to the survivorship of plant species. Coinfection of maize chlorotic mottle virus (MCMV) and the sugarcane mosaic virus (SCMV) causes a deadly disease in maize. An investigation by Liu et al. (2022) showed the role of Zma-miR167 in positively imparting resistance against the MCMV and SCMV. The authors identified ZmARF3 and ZmARF30 as the targets of Zma-miR167. ZmARF3 and ZmARF30 were identified as transcription factors that bind the cis-element in ZmPAO1 promoters to activate its expression. The authors showed how the Zma-miR167-ZmARF3/30-ZmPAO1 module functions differently in resistant and susceptible lines with high expression of Zma-miR167 in resistant lines correlated with the resistant phenotype. Finally, the authors concluded that MCMV-encoded p31 protein enhances ZmPAO1 enzyme activity for its survival in the host.

IntroductionPlant-specific Class III peroxidases (PRXs) play a crucial role in lignification, cell elongation, seed germination, and biotic and abiotic stresses.MethodsThe class III peroxidase gene family in sugarcane were identified by bioinformatics methods and realtime fluorescence quantitative PCR.ResultsEighty-two PRX proteins were characterized with a conserved PRX domain as members of the class III PRX gene family in R570 STP. The ShPRX family genes were divided into six groups by the phylogenetic analysis of sugarcane, Saccharum spontaneum, sorghum, rice, and Arabidopsis thaliana. The analysis of promoter cis-acting elements revealed that most ShPRX family genes contained cis-acting regulatory elements involved in ABA, MeJA, light responsiveness, anaerobic induction, and drought inducibility. An evolutionary analysis indicated that ShPRXs was formed after Poaceae and Bromeliaceae diverged, and tandem duplication events played a critical role in the expansion of ShPRX genes of sugarcane. Purifying selection maintained the function of ShPRX proteins. SsPRX genes were differentially expressed in stems and leaves at different growth stages in S. spontaneum. However, ShPRX genes were differentially expressed in the SCMV-inoculated sugarcane plants. A qRT-PCR analysis showed that SCMV, Cd, and salt could specifically induce the expression of PRX genes of sugarcane.DiscussionThese results help elucidate the structure, evolution, and functions of the class III PRX gene family in sugarcane and provide ideas for the phytoremediation of Cd-contaminated soil and breeding new sugarcane varieties resistant to sugarcane mosaic disease, salt, and Cd stresses.

Copyright of Acta Agronomica Sinica is the property of Crop Science Society of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sugarcane (Saccharum officinarum L.) is a perennial grass, and it is cultivated worldwide for sugar and bioethanol production. During 2020–2021, countrywide field surveys were conducted and indicated the incidence of numerous phytopathogens in sugarcane crop. Infected sugarcane plants showed stunted growth, wilting, leaf yellowing and mosaic pattern in major sugarcane growing provinces of Pakistan (Sindh, Punjab and Khyber Pakhtunkhwa). Diseased plants were collected for the isolation of diseases‐causing pathogen. Wilted canes were cut and placed on potato dextrose agar (PDA) media, and after few days, pathogen was successfully grown on media. Based on fungal morphology and DNA sequence analysis, it was characterized and identified as Fusarium sacchari. Diseased sugarcane samples, showing mosaic symptoms, were collected from 57 locations and were subjected to ELISA test. Out of 570 symptomatic samples, 40 samples were tested positive for Sugarcane mosaic virus (SCMV). These results revealed a higher disease incidence rate (7.01%) of SCMV. This is the first report of countrywide incidence of SCMV in Pakistan. [ABSTRACT FROM AUTHOR]

Previously, sugarcane mosaic virus (SCMV) was developed as a vector for transient expression of heterologous genes in Zea mays (maize). Here, we show that SCMV can also be applied for virus‐induced gene silencing (VIGS) of endogenous maize genes. Comparison of sense and antisense VIGS constructs targeting maize phytoene desaturase (PDS) showed that antisense constructs resulted in a greater reduction in gene expression. In a time course of gene expression after infection with VIGS constructs targeting PDS, lesion mimic 22 (Les22), and Iodent japonica 1 (Ij1), efficient expression silencing was observed 2, 3, and 4 weeks after infection with SCMV. However, at Week 5, expression of Les22 and Ij1 was no longer significantly reduced compared with control plants. The defense signaling molecule jasmonate‐isoleucine (JA‐Ile) can be inactivated by 12C‐hydroxylation and hydrolysis, and knockout of these genes leads to herbivore resistance. JA‐Ile hydroxylases and hydrolases have been investigated in Arabidopsis, rice, and Nicotiana attenuata. To determine whether the maize homologs of these genes function in plant defense, we silenced expression of ZmCYP94B1 (predicted JA‐Ile hydroxylase) and ZmJIH1 (predicted JA‐Ile hydrolase) by VIGS with SCMV, which resulted in elevated expression of two defense‐related genes, Maize Proteinase Inhibitor (MPI) and Ribosome Inactivating Protein 2 (RIP2). Although ZmCYP94B1 and ZmJIH1 gene expression silencing increased resistance to Spodoptera frugiperda (fall armyworm), Schistocerca americana (American birdwing grasshopper), and Rhopalosiphum maidis (corn leaf aphid), there was no additive effect from silencing the expression of both genes. Further work will be required to determine the more precise functions of these enzymes in regulating maize defenses. [ABSTRACT FROM AUTHOR]

Copyright of Acta Agronomica Sinica is the property of Crop Science Society of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Maize lethal necrosis (MLN) is a viral disease caused by a co-infection of maize chlorotic mottle virus (MCMV) and any one of cereal viruses including sugarcane mosaic virus (SCMV), maize dwarf mosaic virus, wheat streak mosaic virus or Johnsongrass mosaic virus. MLN has been identified as the most devastating maize disease that causes the highest yield loss in major maize growing areas in Eastern Africa including Ethiopia. In this study, field assessment, laboratory, and greenhouse experiments were conducted using MCMV and SCMV infected maize residue and infested soil to: (1) assess the role of MLN infected maize residue and infested soil in the transmission of MLN causing viruses, and (2) determine the longevity of the viruses both in the infected maize residue and in the infested soils. Serological detection and back-inoculation test results showed that MCMV was detected and confirmed to be transmitted from infested soil to newly germinated maize seedlings. However, SCMV was neither detected in soil samples from infected fields nor transmitted to maize seedlings. The present study confirmed that MLN infested soil is an essential medium for the survival and spread of MCMV under natural conditions. Under experimental condition, MCMV remained persistent and transmissible up to 6 months to maize planted on MLN infested soil mixed with MLN infected maize residues. Proper management or clearing of crop residues in the field after harvest is necessary to minimize adverse effects of MLN on maize production. Crop rotation is also one of the ways of freeing the soil from MLN disease. [ABSTRACT FROM AUTHOR]

'CP 13‐4100' (Reg. no. CV‐202, PI 698546) sugarcane cultivar (a complex hybrid of Saccharum spp.) was developed through cooperative research conducted by the USDA‐ARS, the University of Florida, and the Florida Sugar Cane League, Inc. The Florida Sugarcane Variety Committee (FSVC) released CP 13‐4100 in June 2020 to growers for commercial cultivation on mineral (sand) soils. It originated from a polycross made at Canal Point (CP) on 3 Dec. 2008 where CP 96‐1252 was the female parent and the male parent was unknown and could be any one of genotypes used in the polycross. CP 13‐4100 was released by FSVC for its high cane and sucrose yields, acceptable commercial recoverable sucrose, and resistances to orange rust, leaf scald, Sugarcane mosaic virus strain E (mosaic), and smut, and acceptable levels of susceptibility to brown rust. CP 13‐4100 and commercial reference checks (i.e., CL 88‐4730, CP 96‐1252, CPCL 97‐2730) yield data were collected from 12 harvests (i.e. three crop cycles—plant cane, first, and second ratoon—at four sand‐soil locations) in final‐stage replicated yield trials. Compared with CL 88‐4730 and CPCL 97‐2730, CP 13‐4100 had significantly (P ≤.0001) higher cane yield (tonnes of cane per hectare: 18.7 and 29.5%), sucrose yield (tonnes of sugar per hectare: 26.3 and 30.7%), and economic index (EI; 10.9–16.9%) and no significant differences from CP 96‐1252 in these traits. CP 13‐4100 tested negative for the Bru1 marker, which is linked to a quantitative major locus of brown rust resistance. CP 13‐4100 could be considered moderately tolerant to freezing among 23 tested genotypes. [ABSTRACT FROM AUTHOR]

Plant pathogens such as viruses are detrimental to the survivorship of plant species. Coinfection of maize chlorotic mottle virus (MCMV) and the sugarcane mosaic virus (SCMV) causes a deadly disease in maize. An investigation by Liu et al. (2022) showed the role of Zma-miR167 in positively imparting resistance against the MCMV and SCMV. The authors identified ZmARF3 and ZmARF30 as the targets of Zma-miR167. ZmARF3 and ZmARF30 were identified as transcription factors that bind the cis-element in ZmPAO1 promoters to activate its expression. The authors showed how the Zma-miR167-ZmARF3/30-ZmPAO1 module functions differently in resistant and susceptible lines with high expression of Zma-miR167 in resistant lines correlated with the resistant phenotype. Finally, the authors concluded that MCMV-encoded p31 protein enhances ZmPAO1 enzyme activity for its survival in the host. [ABSTRACT FROM AUTHOR]

Sugarcane mosaic virus (SCMV; genus Potyvirus) induces maize dwarf mosaic disease that has caused serious yield losses of maize in China. Cross-protection is one of the efficient strategies to fight against severe virus strains. Although many mild strains have been identified, the spontaneous mutation is one of the challenging problems affecting their application in cross-protection. In this study, we found that the substitution of cysteine (C) at positions 57 or 60 in the zinc finger-like motif of HC-Pro with alanine (A; C57A or C60A) significantly reduced its RNA silencing suppression activity and SCMV virulence. To reduce the risk of mild strains mutating to virulent ones by reverse or complementary mutations, we obtained attenuated SCMV mutants with double-mutations in the zinc finger-like and FRNK motifs of HC-Pro and evaluated their potential application in cross-protection. The results showed that the maize plants infected with FKNK/C60A double-mutant showed symptomless until 95 days post-inoculation and FKNK/C60A cross-protected plants displayed high resistance to severe SCMV strain. This study provides theoretical and material bases for the control of SCMV through cross-protection. [ABSTRACT FROM AUTHOR]

Sugarcane mosaic virus (SCMV), belonging to genus Potyvirus, family Potyviridae, is a severe pathogen of several agricultural important crops, mainly sugarcane. Due to complex nature of sugarcane, the effect of SCMV pathogenicity on sugarcane photosynthetic systems remains to be explored. In this study, we investigated the alterations occurring in the photosynthetic system in the sugarcane genotypes at the cytopathological, physiological and biological, transcriptome and proteome level. We generated the transcriptome assembly of two genotypes (susceptible Badila and resistant B-48) using Saccharum spontaneum L. as a reference genome. RNA-sequencing data revealed the significant upregulation of NAD(P)H, RubisCO, oxygen-evolving complex, chlorophyll a and b binding protein, Psb protein family, PSI reaction center subunit II, and IVgenes in B-48, as compared to its counterparts. Upregulated genes in B-48 are associated with various processes such as stability and assembly of photosystem, protection against photoinhibition and antiviral defense. The expression pattern of differentially abundant genes were further verified at the proteomics level. Overall, differentially expressed genes/proteins (DEGs/DEPs) showed the consistency of expression at both transcriptome and proteome level in B-48 genotype. Comprehensively, these data supported the efficiency of B-48 genotype under virus infection conditions and provided a better understanding of the expression pattern of photosynthesis-related genes in sugarcane. [ABSTRACT FROM AUTHOR]

Sugarcane mosaic disease is a major threat to sugarcane cultivation worldwide. Under Indian conditions, mosaic disease is caused by Sugarcane streak mosaic virus (SCSMV) and Sugarcane mosaic virus (SCMV) either alone or together. A "0–6" scale mosaic severity grading system has been developed after analysing the phenotypic expression of mosaic symptoms in ~ 210 genotypes comprising of cultivated species (Saccharum officinarum, S. sinense and S. barberi), wild species (S. spontaneum and S. robustum) and hybrid-varieties at two diverse environments over a period of three years. They were also screened for the presence of SCSMV and SCMV by RT-PCR assays. Out of the 210 genotypes, only 7 were free of mosaic viruses, indicating the rare possibility of getting resistant genotypes among the world collection of sugarcane germplasm. It also clearly indicates that the mosaic disease is widespread in occurrence and nearly 97% of the varieties/genotypes were infected with mosaic viruses. Overall, the presence of SCSMV, SCMV and both the viruses were recorded in 77 (87.5%), 51 (58%) and 46 (52%) of the 88 species-clones indexed through RT-PCR assays. The hybrid-varieties with mosaic grade of 6 often had mixed infections of both the mosaic viruses, resulting in severe symptom expression and degeneration. The 0–6 scale mosaic phenotyping developed in this study will be useful to screen the world sugarcane germplasm collections against the mosaic disease. The study identified three S. robustum genotypes as resistant to mosaic, indicating the possibility of identifying resistant sources and these may serve as donors for mosaic resistance. [ABSTRACT FROM AUTHOR]

Abstract Background Cannas are popular ornamental plants and widely planted for the beautiful foliage and flower. Viral disease is a major threaten to canna horticulture industry. In the city of Beijing, mosaic disease in canna was frequently observed, but the associated causal agent and its biological characterization is still unknown. Results After small RNA deep sequencing, 36,776 contigs were assembled and 16 of them shared high sequence identities with the different proteins of Sugarcane mosaic virus (SCMV) of the size ranging from 86 to 1911 nt. The complete genome of SCMV isolate (canna) was reconstructed by sequencing all cDNA clones obtained from RT-PCR and 5′\3′ RACE amplifications. SCMV-canna isolate showed to have a full RNA genome of 9579 nt in length and to share 78% nt and 85% aa sequence identities with SCMV isolates from other hosts. The phylogenetic tree constructed based on the full genome sequence of SCMV isolates allocated separately the canna-isolate in a distinct clade, indicating a new strain. Recombination analyses demonstrated that SCMV-canna isolate was a recombinant originating from a sugarcane-infecting isolate (major parent, acc. no. AJ310103) and a maize-infecting isolate (minor parent, acc. no. AJ297628). Pathogenicity test showed SCMV-canna could cause typical symptoms of mosaic and necrosis in some tested plants with varying levels of severity but was less virulent than the isolate SCMV-BJ. Field survey showed that the virus was widely distributed. Conclusions This study identified SCMV as the major agent causing the prevalent mosaic symptom in canna plants in Beijing and its genomic and biological characterizations were further explored. All these data enriched the knowledge of the viruses infecting canna and would be helpful in effective disease management in canna.

Sugarcane mosaic virus (SCMV; genus Potyvirus) induces maize dwarf mosaic disease that has caused serious yield losses of maize in China. Cross-protection is one of the efficient strategies to fight against severe virus strains. Although many mild strains have been identified, the spontaneous mutation is one of the challenging problems affecting their application in cross-protection. In this study, we found that the substitution of cysteine (C) at positions 57 or 60 in the zinc finger-like motif of HC-Pro with alanine (A; C57A or C60A) significantly reduced its RNA silencing suppression activity and SCMV virulence. To reduce the risk of mild strains mutating to virulent ones by reverse or complementary mutations, we obtained attenuated SCMV mutants with double-mutations in the zinc finger-like and FRNK motifs of HC-Pro and evaluated their potential application in cross-protection. The results showed that the maize plants infected with FKNK/C60A double-mutant showed symptomless until 95 days post-inoculation and FKNK/C60A cross-protected plants displayed high resistance to severe SCMV strain. This study provides theoretical and material bases for the control of SCMV through cross-protection.

Maize dwarf mosaic (MDM) is one of the most important virus diseases of maize worldwide. Caused by the potyviruses maize dwarf mosaic virus (MDMV) or sugarcane mosaic virus (SCMV), MDM can cause up to 90% yield loss in susceptible hybrids. One of the most effective management strategies for MDM is growing potyvirus-resistant corn varieties. However, yield impacts associated with MDM and the corresponding efficacy of genetic resistance present in modern United States commercial hybrid lines is uncharacterized. In this study, we evaluated the disease response of 78 commercial hybrids to MDMV and SCMV and quantified yield losses associated with infection over multiple trials. We determined that while 97% of the hybrids tested were resistant to MDMV, 100% were susceptible to SCMV, with mean disease incidence per line averaging between 45 and 78% across six trial years. Despite only one hybrid displaying visible mosaic symptoms when inoculated with MDMV, MDMV reduced average yields by approximately 5% across all hybrids compared with the mock-inoculated treatment. The yield impact of SCMV was more severe, reducing average yields by 10% across replicated experiments. These results indicate that while most commercial hybrids are resistant to MDMV, possibly due to the presence of the major Scmv1 resistance locus on chromosome 6, additional potyvirus resistance genes are needed to manage SCMV-induced MDM. Pyramiding resistance loci, such as Scmv2 on chromosome 3 or Scmv3 on chromosome 10 in addition to Scmv1 , could be an effective strategy to mitigate the yield impact of MDM disease., Competing Interests: The author(s) declare no conflict of interest.

Maize viral diseases especially maize dwarf mosaic disease (MDMD), which is caused by potyviruses, lead to significant crop losses worldwide. Aim. The aim of this work was to identify the causal agent of mosaic symptoms, observed on maize plants during 2018--2020 in Kyiv region. Methods. Enzyme-linked immunosorbent assay in the DAS-ELISA modification using commercial Loewe Biochemica test systems for Maize dwarf mosaic virus (MDMV), Sugarcane mosaic virus (SCMV), Wheat streak mosaic virus (WSMV) were applied to identify the causal agent of maize disease in collected samples. Transmission electron microscopy was used in order to direct viral particle visualisation. Aphids, which are natural vectors of plant viruses, were found on diseased plants. Results. Plants with typical mosaic symptoms were observed in corn crops of the Kyiv region in early June 2018. The pathogen was transmitted by mechanical inoculation to maize and sweet maize plants with the manifestation of mosaic symptoms. Electron microscopy of the sap from diseased plants revealed the presence of flexible filamentous virions 750 nm long and 13 nm in diameter, typical for the genus Potyvirus. In August, mosaic symptoms and aphids Rhopalosiphum padi were found on previously healthy plants in the same maize crop. In 2020, in the same sown area, maize plants were free of viral infection during inspection in June, but a re-inspection in September revealed mosaic symptoms on maize crop and the presence of aphids in the leaf axils. The presence of SCMV in maize samples collected in June and August/September 2018 and 2020, as well as in inoculated maize and sweet maize plants, was confirmed by ELISA using a commercial test system. The obtained data allow suggesting that Rhopalosiphum padi is a natural vector of SCMV in agrocenoses of Ukraine. It should be noted that co-infection with MDMV and WSMV in the affected plants was not detected. Conclusions. This study presents the first report of SCMV in maize in Ukraine. [ABSTRACT FROM AUTHOR]

Copyright of Acta Agronomica Sinica is the property of Crop Science Society of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Maize lethal necrosis (MLN) disease caused by double infection of Maize chlorotic mottle virus (MCMV) and Sugarcane mosaic virus (SCMV) has become a major maize production constraint in Ethiopia. A field survey was conducted in areas where MLN infection was reported to identify naturally infected alternate hosts. MCMV host range was also studied by artificially inoculating various weed species in the greenhouse to determine potential alternate hosts. Using the serological method of double‐antibody sandwich enzyme‐linked immunosorbent assay (DAS‐ELISA) test, MCMV was detected in 23 (20.35%), and SCMV was detected in 4 (3.53%) of 113 MLN symptomatic samples collected from the field, while combined infection of both viruses was detected in 11 (9.73%) of the samples. Poaceae family had the highest number of grass species that were alternate hosts for MLN causing viruses. Digitaria sanguinalis, Phalaris paradoxa, Oplismenus hirtellus, Echinocloa colona, Cynodon nlemfuensis, Pennisetum purpureum from Poaceae and Cyperus cyperoids from Cyperaceae family were naturally infected by MCMV. Cyperus rotundus, sugarcane (Saccharum officinarum) and sorghum (Sorghum bicolor) were infected by both MCMV and SCMV under natural field conditions. In addition, seed transmission study was conducted using growing‐on tests to determine the potential of seed transmission and its role in the spread of MLN. Overall mean seed to the seedling transmission rate was 0.073% with a range of 0 to 0.17% among 20 different maize varieties studied. Fourteen maize genotypes had some levels of seed transmission (0.03%–0.017%) for MCMV, whereas, SCMV seed transmission was observed only in a single plant of one genotype, with an overall mean of only 0.003%. Seed transmission rates of the viruses were influenced by the seed lot and maize varieties used. The wide ranges of natural and experimental alternate hosts and seed transmissibility of MLN causing viruses suggest that the viruses play a greater role in MLN epidemiology. [ABSTRACT FROM AUTHOR]

Sugarcane mosaic virus (SCMV) is a serious disease of monocotyledonous plants, including sugarcane, causing deterioration in both growth and productivity. RNA interference (RNAi) inhibits gene expression through RNA-mediated sequence-specific interactions and is considered an effective approach to control viral infection in plants. In this study, the SCMVCp gene encoding the coat protein (CP) was inserted into the pGreen-0179 plasmid in both sense and antisense orientations. Cauliflower mosaic virus (CaMV) and Zea mays ubiquitin (Ubi) promoters were selected to drive the transcription of the intron-hairpin constructs, called HpSCMVCp-CaMV and HpSCMVCp-Ubi, respectively. Transgenic sugarcane expressing these constructs was generated through Agrobacterium-mediated transformation. This transformation method produced a high percentage of transgenic plants for both HpSCMVCp-CaMV and HpSCMVCp-Ubi, as confirmed by PCR analysis. Southern blotting revealed a single stable insertion of the DNA target in the genome of transgenic sugarcane lines. After artificial virus infection, lines that developed mosaic symptoms were classified as susceptible, whereas those that remained green without symptoms were classified as resistant at 42 days post-inoculation. Immunoblotting revealed CP expression at 37 kDa in susceptible and non-transgenic sugarcane, but not in resistant lines. RT-PCR analysis confirmed viral Cp and Nib gene expression in susceptible lines and their absence in resistant lines. Interestingly, upon comparison of effectivity, CaMV and Ubi promoter-driven gene expression resulted in 57.69% and 82.35% resistant sugarcane lines, respectively. Thus, we concluded that RNAi is effective for inducing resistance against SCMV and that the Ubi promoter is an effective promoter for producing transgenic sugarcane. [ABSTRACT FROM AUTHOR]

Copyright of Revista de la Universidad del Valle de Guatemala is the property of Universidad del Valle de Guatemala and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Agronomica Sinica is the property of Crop Science Society of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Among the most important diseases in Saccharum spp., sugarcane yellow leaf virus (SCYLV) and sugarcane mosaic virus (SCMV) stand out. In Carica papaya L., papaya ringspot virus (PRSV-P) causes one of the most destructive diseases. The objective of this research was to determine the distribution in Cuba of these viruses and their molecular characterization. Prospecting and molecular diagnosis were carried out by RT-PCR. In the case of SCMV, direct sequencing was performed. Phylodynamic analyzes were performed with 34 sequences from Cuban PRSV-P isolates and 107 sequences from isolates from the American continent and Caribbean islands. SCYLV and PRSV-P are widely distributed in Cuba. From SCYLV the existence of the races BRA-PER, CUB and REU was reported, and from SCMV a single race. The Cuban isolates of PRSV-P and from the American continent and Caribbean islands showed a common ancestor. SCYLV and PRSV-P constitute a potential hazard to farmers. [ABSTRACT FROM AUTHOR]

Cross-protection is a promising measure to control plant viral diseases. Reverse genetics had been recently adopted to generate attenuated mutants that have potential in cross-protection. But studies on the variability of the progeny viruses of the attenuated mutants are scarce. Sugarcane mosaic virus (SCMV; genus Potyvirus, family Potyviridae) is the prevalent virus inducing maize dwarf mosaic disease in China. Here, we showed that the substitution of arginine with isoleucine in the FRNK motif at position 184 of helper component-proteinase (HC-Pro) abolished its RNA silencing suppression (RSS) activity, drastically reduced the virulence and accumulation level of SCMV, and impaired the synergism between SCMV and maize chlorotic mottle virus. The attenuated mutant could protect maize plants from a severe infection of SCMV. However, a spontaneous mutation of glycine at position 440 to arginine in HC-Pro rescued the virulence and synergism with maize chlorotic mottle virus of SCMV and the RSS activity of HC-Pro. Similar results were obtained with tobacco vein banding mosaic virus and watermelon mosaic virus. These results provide novel evidence for the complementary mutation of potyviruses in maintaining the HC-Pro RSS activity and potyviral virulence and remind us of evaluating the potential risk of attenuated mutants thoroughly before applying for the control of plant viral diseases via cross-protection.

Cross-protection is a promising measure to control plant viral diseases. Reverse genetics had been recently adopted to generate attenuated mutants that have potential in cross-protection. But studies on the variability of the progeny viruses of the attenuated mutants are scarce. Sugarcane mosaic virus (SCMV; genus Potyvirus , family Potyviridae) is the prevalent virus inducing maize dwarf mosaic disease in China. Here, we showed that the substitution of arginine with isoleucine in the FRNK motif at position 184 of helper component-proteinase (HC-Pro) abolished its RNA silencing suppression (RSS) activity, drastically reduced the virulence and accumulation level of SCMV, and impaired the synergism between SCMV and maize chlorotic mottle virus. The attenuated mutant could protect maize plants from a severe infection of SCMV. However, a spontaneous mutation of glycine at position 440 to arginine in HC-Pro rescued the virulence and synergism with maize chlorotic mottle virus of SCMV and the RSS activity of HC-Pro. Similar results were obtained with tobacco vein banding mosaic virus and watermelon mosaic virus. These results provide novel evidence for the complementary mutation of potyviruses in maintaining the HC-Pro RSS activity and potyviral virulence and remind us of evaluating the potential risk of attenuated mutants thoroughly before applying for the control of plant viral diseases via cross-protection. [ABSTRACT FROM AUTHOR]

Maize lethal necrosis disease (MLND) is a devastating viral disease of maize caused by double infection with Maize chlorotic mottle virus (MCMV) and any one of the Potyviridae family members. Management of MLND requires effective resistance screening and surveillance tools. In this study, we report the use of small RNA (sRNA) profiling to detect MLND causal viruses and further the development of alternative detection markers for use in routine surveillance of the disease‐causing viruses. Small RNAs (sRNAs) originating from five viruses namely MCMV, Sugarcane mosaic virus (SCMV), Maize streak virus (MSV), Maize‐associated totivirus (MATV) and Maize yellow mosaic virus (MYMV) were assembled from infected maize samples collected from MLND hot spots in Kenya. The expression of the identified viral domains was further validated using quantitative real‐time PCR. New markers for the detection of some of the MLND causal viruses were also developed from the highly expressed domains and used to detect the MLND‐causative viruses in maize and alternative hosts. These findings further demonstrate the potential of using sRNAs especially from highly expressed viral motifs in the detection of MLND causal viruses. We report the validation of new sets of primers for use in detection of the most common MLND causal viruses MCMV and SCMV in East Africa. [ABSTRACT FROM AUTHOR]

Sugarcane mosaic virus (SCMV) is distributed worldwide and infects three major crops: sugarcane, maize, and sorghum. The impact of SCMV is increased by its interaction with Maize chlorotic mottle virus which causes the synergistic maize disease maize lethal necrosis. Here, we characterised maize lethal necrosis-infected maize from multiple sites in East Africa, and found that SCMV was present in all thirty samples. This distribution pattern indicates that SCMV is a major partner virus in the East African maize lethal necrosis outbreak. Consistent with previous studies, our SCMV isolates were highly variable with several statistically supported recombination hot- and cold-spots across the SCMV genome. The recombination events generate conflicting phylogenetic signals from different fragments of the SCMV genome, so it is not appropriate to group SCMV genomes by simple similarity. [ABSTRACT FROM AUTHOR]

Summary: Sugarcane mosaic virus (SCMV) is a pathogen of worldwide importance that causes dwarf mosaic disease on maize (Zea mays). Until now, few maize genes/proteins have been shown to be involved in resistance to SCMV. In this study, we characterized the role of maize phenylalanine ammonia‐lyases (ZmPALs) in accumulation of the defence signal salicylic acid (SA) and in resistance to virus infection. SCMV infection significantly increased SA accumulation and expression of SA‐responsive pathogenesis‐related protein genes (PRs). Interestingly, exogenous SA treatment decreased SCMV accumulation and enhanced resistance. Both reverse transcription‐coupled quantitative PCR and RNA‐Seq data confirmed that expression levels of at least four ZmPAL genes were significantly up‐regulated upon SCMV infection. Knockdown of ZmPAL expression led to enhanced SCMV infection symptom severity and virus multiplication, and simultaneously resulted in decreased SA accumulation and PR gene expression. Intriguingly, application of exogenous SA to SCMV‐infected ZmPAL‐silenced maize plants decreased SCMV accumulation, showing that ZmPALs are required for SA‐mediated resistance to SCMV infection. In addition, lignin measurements and metabolomic analysis showed that ZmPALs are also involved in SCMV‐induced lignin accumulation and synthesis of other secondary metabolites via the phenylpropanoid pathway. In summary, our results indicate that ZmPALs are required for SA accumulation in maize and are involved in resistance to virus infection by limiting virus accumulation and moderating symptom severity. [ABSTRACT FROM AUTHOR]

Sugarcane mosaic virus (SCMV) is one of the most damaging viruses infecting sugarcane, maize and some other graminaceous species around the world. To investigate the genetic diversity of SCMV in Iran, the coat protein (CP) gene sequences of 23 SCMV isolates from different hosts were determined. The nucleotide sequence identity among Iranian isolates was more than 96%. They shared nucleotide identities of 75.5–99.9% with those of other SCMV isolates available in GenBank, the highest with the Egyptian isolate EGY7-1 (97.5–99.9%). The results of phylogenetic analysis suggested five divergent evolutionary lineages that did not completely reflect the geographical origin or host plant of the isolates. Population genetic analysis revealed greater between-group than within-group evolutionary divergence values, further supporting the results of the phylogenetic analysis. Our results indicated that natural selection might have contributed to the evolution of isolates belonging to the five identified SCMV groups, with infrequent genetic exchanges occurring between them. Phylogenetic analyses and the estimation of genetic distance indicated that Iranian isolates have low genetic diversity. No recombination was found in the CP cistron of Iranian isolates and the CP gene was under negative selection. These findings provide a comprehensive analysis of the population structure and driving forces for the evolution of SCMV with implications for global exchange of sugarcane germplasm. Gene flow, selection and somehow homologous recombination were found to be the important evolutionary factors shaping the genetic structure of SCMV populations.

Introduction: Several potyviruses infecting gramineous plants have been reported from Iran. Mosaic is the most widespread viral disease affecting sugarcane and maize production. Sugarcane mosaic virus (SCMV) is one of the causal agents of mosaic disease, which was first described in Ohio in 1963. SCMV belonging to the genus Potyvirus, family Potyviridae, is a single-stranded positive sense RNA virus which can infect gramineous plants such as sugarcane, maize and sorghum. Like all potyviruses, SCMV has non-enveloped flexuous filamentous virions of 750 nm long and 11–13 nm wide, which encapsidate a single-stranded, positive-sense RNA molecule of approximately 10,000 nt long. SCMV subgroup in the genus Potyvirus consists of seven different species viz., SCMV, Sorghum mosaic virus (SrMV), Maize dwarf mosaic virus (MDMV), Johnsongrass mosaic virus (JGMV); Sorghum mosaic virus (SrMV), Zea mosaic virus (ZeMV), Pennisetum mosaic virus (PenMV) and Cocksfoot streak virus (CSV). These viruses have been transmitted by aphids in a non-persistent manner, and cause mosaic disease and yield loss in sugarcane, maize, sorghum, and other gramineous plants. Among these viruses, only SCMV and SrMV are known to infect sugarcane under natural conditions and are considered as the causal agents of sugarcane mosaic disease. SCMV causes yield losses in many countries, and losses of maize production have been estimated at 30–80%, making it the most economically important problem in world maize production. The first report of SCMV in Iran was from Khuzestan province in 1993. There are also partial sequences, mostly from the 3'-UTR and coat protein regions, of some isolates of this virus in Iran. As Mazandaran province in North of Iran is one of the major producing areas of maize and sugarcane, identification of this virus is a concern. The purpose of this research was to study the existence of SCMV in research areas and determining of its phylogenetic relationship. Materials and Methods: From July to September 2013 and 2014, a total of 45 leaf samples of maize and sugarcane showing virus symptoms were collected from different maize and sugarcane fields in Mazandaran province. Total RNA was extracted from all samples. First-strand cDNA and PCR amplification were carried out with an SCMV-specific primer F4/R3 corresponding to the virus CP gene. Expected PCR products of 900 bp were purified from 1% agarose gels using Gel Recovery kit, then cloned into the pTG19-T vector and sequenced. Sequences were compared to data available in the GenBank. Phylogenetic tree for grouping based on nucleotide sequences was constructed by MEGA 6 software program using the neighbor-joining method. Multiple alignments of the nucleotide and amino acid sequences were carried out using the ClustalW and DNAMAN7 software. Results and Discussion: Amplification product (900 bp) was obtained from 35 infected samples, but not from healthy samples. The most typical symptoms in positive samples were mosaic, mosaic strips, and yellow chlorotic stripes. Four selected PCR positive samples were cloned into the pTG19-T vector and sequenced. BLASTn analysis of the sequenced data revealed that the PCR-amplified fragments belonged to CP gene of SCMV. Four selected isolates named Maz-SCR1 and Maz-SCR2 from sugarcane (Ghaemshahr), Maz-MR from maize (Ghaemshahr) and Maz-MB from maize (Babolsar). Phylogenetic tree based on multiple sequence alignment of CP gene divided all SCMV isolates into two groups: I and II. Members of each group were divided into two subgroups: A, B. Mazandaran isolates of SCMV were grouped with isolates of Khuzestan and Egypt in a subclade in subgroup IA. Phylogenetic analysis showed that Mazandaran isolates share 78 to 99 % nucleotide sequence identity and 79.5-100 % amino acid sequence identity with other isolates of SCMV. Also, the identity of these four isolates in the nucleotide and amino acid levels ranged between 97 to 98.9 % and 99.3 to 100 %, with each other, respectively. Isolate of Mazandaran showed the highest nucleotide sequence identity with khzL66 and khzQ86 isolates from Khuzestan (between 96.6 to 98.8 %) and EGY7-1 isolate from Egypt (between 96.7 to 99 %) and the lowest nucleotide sequence identity with BD8 isolate from China (between 78 to 78.8 %). The previously identified and conserved amino acid sequence motifs described in CP of potyviruses were present in Mazandaran isolates CP gene. Conclusion: SCMV is a widespread cereal potyvirus in the world and often occurs in a mixed infection with SrMV. In this study, for the first time, we reported the occurrence of SCMV in maize and sugarcane fields in Mazandaran province based on CP gene analyses and determined its phylogenetic relationship with other SCMV isolates available in the GenBank. Iranian isolates of SCMV were grouped with the isolate of Egypt in a subclade in subgroup IA. It is speculated that the Iranian isolates have been introduced into this country with sugarcane cuttings. The data obtained in this study will be beneficial to improve control strategies for this virus in Iran. Identification and the use of more isolates and analysis of genes in addition to CP are recommended for a better understanding of the genetic structure and variation of SCMV populations on a large geographical scale.

Maize lethal necrosis (MLN) disease caused by a combined infection of Maize chlorotic mottle virus (MCMV) and any cereal infecting potyvirus is a threat to food security in Sub-Saharan Africa (SSA). Resistance to potyvirus has been extensively studied and Mdm1 gene for potyvirus resistance on chromosome 6 of maize is linked to Y1 gene for maize endosperm colour. This study is aimed at selecting for coupling-phase recombination of potyvirus resistance and white endosperm colour. White susceptible maize lines CML333 and CML277 were crossed with a yellow resistant line, Pa405, to produce F1 and F2 progenies. Progenies were screened using molecular markers to recover 22 white endosperm recombinants. 22 selections were advanced to F3 recombinant families, and 10 were assayed for their responses to Maize dwarf mosaic virus (MDMV) and Sugarcane mosaic virus (SCMV). Four families segregated for SCMV resistance, selection of homozygous recombinants within these families will provide lines appropriate for improving lines with resistance to SCMV and MLN resistance in SSA. [ABSTRACT FROM AUTHOR]