Wheat Streak Research Articles

Wheat streak mosaic virus: transmission, its impact, and crop protection strategies—a systematic review

Wheat streak mosaic virus: transmission, its impact, and crop protection strategies—a systematic review

Plant Viral Synergism: Co-Expression of P1 and NIa-Pro Cistrons of Wheat Streak Mosaic Virus and Triticum Mosaic Virus Is Required for Synergistic Interactions in Wheat.

Synergistic interactions among unrelated viruses in mixed infections can cause significant yield losses, and viral determinants of these interactions are poorly understood. Wheat (Triticum aestivum L.) co-infection with wheat curl mite-transmitted wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) results in disease synergism with a drastically increased symptom phenotype of stunted growth, leaf bleaching, and enhanced titers of both viruses. In this study, we examined the viral determinants responsible for WSMV-TriMV disease synergism through transient expression of select cistrons of WSMV in wheat through TriMV and vice-versa. We found that expression of WSMV P1, NIa, or NIaPro cistrons in wheat through TriMV or vice-versa elicited moderate to severe symptoms with a moderate or no increase in virus titer. However, co-expression of P1 and NIaPro cistrons of WSMV in wheat through TriMV or vice-versa exhibited a WSMV-TriMV disease synergism-like phenotype. Additionally, we found that the P3 cistron of both viruses is dispensable for synergism, whereas HCPro and NIaVPg cistrons of WSMV and TriMV are not the primary determinants but might have a minor role in efficient synergism. In co-infected wheat, accumulation of vsiRNAs was increased, similar to viral genomic RNA copies, despite the presence of dual viral RNA silencing suppressors (VRSS), which function through sequestration of vsiRNAs. Our findings revealed that WSMV-TriMV disease synergism is not caused by the suppression of host post-transcriptional gene silencing by dual VRSS in co-infected wheat and the P1 and NIaPro cistrons of both viruses collectively drive synergistic interactions between WSMV and TriMV in wheat.

Phytoplasma etiology and epidemiology of wheat streak and stunting disease in Central India.

The online version contains supplementary material available at 10.1007/s13205-024-04114-3.

Viromes of Monocotyledonous Weeds Growing in Crop Fields Reveal Infection by Several Viruses Suggesting Their Virus Reservoir Role.

In 2019, random samples of Panicum miliaceum growing as a weed were surveyed to uncover their virus infections at two locations in Hungary. This pilot study revealed infection with three viruses, two appearing for the first time in the country. As follow-up research, in the summer of 2021, we collected symptomatic leaves of several monocotyledonous plants in the same locations and determined their viromes using small RNA high-throughput sequencing (HTS). As a result, we have identified the presence of wheat streak mosaic virus (WSMV), barley yellow striate mosaic virus (BYSMV), barley virus G (BVG), and two additional viruses, namely Aphis glycines virus 1 (ApGlV1) and Ljubljana dicistrovirus 1 (LDV1), which are described for the first time in Hungary. New hosts of the viruses were identified: Cynodon dactylon is a new host of BYSMV and LDV1, Echinocloa crus-galli is a new host of BVG, ApGlV1 and LDV1, Sorghum halepense is a new host of ApGlV1, and Panicum miliaceum is a new host of LDV1. At the same time, Zea mays is a new host of ApGlV1 and LDV1. Small RNA HTS diagnosed acute infections but failed to detect persistent ones, which could be revealed using RT-PCR. The infection rates at the different locations and plant species were different. The phylogenetic analyses of the sequenced virus variants suggest that the tested monocotyledonous weeds can host different viruses and play a virus reservoir role. Viral spread from the reservoir species relies on the activity of insect vectors, which is why their management requires an active role in plant protection strategies, which need careful planning in the changing environment.

First report of Triticum mosaic virus infecting oat crop in the United States.

Triticum mosaic virus (TriMV, genus Poacevirus, family Potyviridae) was first reported in 2006 (Seifers et al. 2008) to infect wheat, and since then, it has been established as a constraint for US wheat production (Byamukama et al. 2013). In the field, TriMV often exists as a coinfection with wheat streak mosaic virus (WSMV), and these two viruses interact synergistically to produce severe symptoms and greater yield loss (Byamukama et al. 2012; Tatineni et al. 2022). Both TriMV and WSMV are transmitted by wheat curl mites (Aceria tosichella Keifer) (McMechan et al. 2014). Wheat is the primary host reported for TriMV in the field, but Seifers et al. (2010) established oat, rye, barley, and several other cereals and grasses as hosts under controlled conditions. However, there are no documented cases of TriMV infecting oats in the field. Between 10-25 June, 2023, a total of 273 field oat plants showing foliar yellowing, yellow flecking, and streaking symptoms were collected from four different fields in Nebraska (Big Springs: 41.1029° N, 102.1451° W; Mead: 41.2292° N, 96.4938° W; Odell: 40.0459° N, 96.7984° W; Stumf: 40.5048° N, 101.4223° W). Total RNA was extracted using the MagMax Plant RNA Isolation kit (Thermo Fisher Scientific) and the KingFisher Flex Magnetic Particle Processor (Thermo Fisher Scientific) (Mondal et al. 2023). Sample RNA was assayed with a single-step multiplex reverse transcription polymerase chain reaction (RT-PCR) to determine presence of WSMV and TriMV. Out of 273 symptomatic oat plants, 254 (93.04%) tested positive for at least one virus. Out of total positive samples, 238 were positive for WSMV (93.70 %), 12 plants tested positive for both TriMV and WSMV (4.70%), and 4 plants were infected with TriMV alone (1.60%). As a secondary confirmation, amplified fragments from the TriMV single infection were gel purified using a gel extraction kit (QIAquick) and sequenced (Eurofins Genomics). The nucleotide sequences were analysed using the BlastN program, compiled, and edited in the BioEdit software (Hall 1999). Sequences were deposited in the NCBI GenBank database (accession number PP475806). Nucleotide BLAST searches of the target coat protein (CP) gene showed > 98% identity to the corresponding sequences in TriMV accession MK318274. For further validation, virus inoculum was prepared by grinding field-collected plant material from plants with only TriMV present in 20 mM sodium phosphate buffer, pH 7.0, and then mechanically inoculating two-week-old oats (cv. Shaw n=8) and wheat (cv. Sattler, n=8) plants. Three weeks post-inoculation, all the eight wheat plants exhibited mild yellowing and streaking symptoms, while oat plants did not show obvious foliar symptoms. All wheat and oat plants were further tested positive with DAC-ELISA (antibodies produced against TriMV CP at the USDA-ARS facility in Lincoln, NE) and with RT-PCR. The specific attribution of these symptoms to TriMV in oats is not possible as none produced prominent symptoms. Asymptomatic oat infection from symptomatic field-collected oat samples could be due to oat cultivar differences. Although the prevalence of TriMV in wheat has been established across the Great Plains of the United States, to our knowledge, this is the first report of TriMV infection in US oat fields. Our finding warrant further investigation into the incidence and impact of the virus in oat crop and its potential for serving as a asymptomatic virus reservoir.

Helper Component-Proteinase of Triticum Mosaic Virus Is a Viral Determinant of Wheat Curl Mite Transmission.

Triticum mosaic virus (TriMV; genus Poacevirus; family Potyviridae) is an economically important virus in the Great Plains region of the United States. TriMV is transmitted by the wheat curl mite (Aceria tosichella) Type 2 genotype but not by Type 1. Helper component-proteinase (HC-Pro) is a vector transmission determinant for several potyvirids, but the role of HC-Pro in TriMV transmission is unknown. In this study, we examined the requirement of the HC-Pro cistron of TriMV for wheat curl mite (Type 2) transmission through deletion and point mutations and constructing TriMV chimeras with heterologous HC-Pros from other potyvirids. TriMV with complete deletion of HC-Pro failed to be transmitted by wheat curl mites at detectable levels. Furthermore, TriMV chimeras with heterologous HC-Pros from aphid-transmitted turnip mosaic virus and tobacco etch virus, or wheat curl mite-transmitted wheat streak mosaic virus, failed to be transmitted by wheat curl mites. These data suggest that heterologous HC-Pros did not complement TriMV for wheat curl mite transmission. A decreasing series of progressive nested in-frame deletions at the N-terminal region of HC-Pro comprising amino acids 3 to 125, 3 to 50, 3 to 25, 3 to 15, 3 to 8, and 3 and 4 abolished TriMV transmission by wheat curl mites. Additionally, mutation of conserved His20, Cys49, or Cys52 to Ala in HC-Pro abolished TriMV transmissibility by wheat curl mites. These data suggest that the N-terminal region of HC-Pro is crucial for TriMV transmission by wheat curl mites. Collectively, these data demonstrate that the HC-Pro cistron of TriMV is a viral determinant for wheat curl mite transmission.

The nearly complete genome sequence of clade B, wheat streak mosaic virus isolate from Türkiye

The nearly complete genome sequence of clade B, wheat streak mosaic virus isolate from Türkiye

Investigation of Metabolic Responses in Virus-infected Wheat (Triticum aestivum L.) Grown in Azerbaijan

Barley yellow dwarf viruses (BYDV), Wheat streak mosaic virus (WSMV), Wheat dwarf virus (WDV), and Soil-borne wheat mosaic virus (SBWMV) constitute the most dangerous and widespread viruses affecting cereals across all wheat-growing regions worldwide. While numerous foreign scientific reports focus on the impact of climate change on plants, pathogens, and their vectors, only a limited number of studies address cereal viruses. The objective of this study was to investigate the variability of economically significant wheat viruses in several regions of Azerbaijan and to identify certain metabolic enzymes such as malate dehydrogenase (MDH), aspartate aminotransferase (AsAT), and alanine aminotransferase (ALAT) in virus-infected wheat samples. During 2022-2023, it was observed that BYDV and WSMV alternated in prevalence from year to year, with no instances of co-infection recorded. SBWMV was not detected in the tested samples. WSMV incidence rates were 12.4% and 19% in 2022 and 2023, respectively, whereas BYDV was detected at rates of 14.6% and 8.5%, respectively. Our results support a tight relationship between amino acid metabolism and stress responses. The results of the research allow the conclusion that mitochondrial NAD-MDH implements oxidation of NADH reduced in the reaction of glycine decarboxylation during photorespiration and intensifies biosynthesis of 2-oxoglutarate playing the role of the carbon skeleton in the synthesis of amino acids.

Differential regulation of miRNAs involved in the susceptible and resistance responses of wheat cultivars to wheat streak mosaic virus and Triticum mosaic virus

BackgroundWheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) are components of the wheat streak mosaic virus disease complex in the Great Plains region of the U.S.A. and elsewhere. Co-infection of wheat with WSMV and TriMV causes synergistic interaction with more severe disease symptoms compared to single infections. Plants are equipped with multiple antiviral mechanisms, of which regulation of microRNAs (miRNAs) is a potentially effective constituent. In this investigation, we have analyzed the total and relative expression of miRNA transcriptome in two wheat cultivars, Arapahoe (susceptible) and Mace (temperature-sensitive-resistant), that were mock-inoculated or inoculated with WSMV, TriMV, or both at 18 °C and 27 °C.ResultsOur results showed that the most abundant miRNA family among all the treatments was miRNA166, followed by 159a and 168a, although the order of the latter two changed depending on the infections. When comparing infected and control groups, twenty miRNAs showed significant upregulation, while eight miRNAs were significantly downregulated. Among them, miRNAs 9670-3p, 397-5p, and 5384-3p exhibited the most significant upregulation, whereas miRNAs 319, 9773, and 9774 were the most downregulated. The comparison of infection versus the control group for the cultivar Mace showed temperature-dependent regulation of these miRNAs. The principal component analysis confirmed that less abundant miRNAs among differentially expressed miRNAs were strongly correlated with the inoculated symptomatic wheat cultivars. Notably, miRNAs 397-5p, 398, and 9670-3p were upregulated in response to WSMV and TriMV infections, an observation not yet reported in this context. The significant upregulation of these three miRNAs was further confirmed with RT-qPCR analysis; in general, the RT-qPCR results were in agreement with our computational analysis. Target prediction analysis showed that the miRNAs standing out in our analysis targeted genes involved in defense response and regulation of transcription.ConclusionInvestigation into the roles of these miRNAs and their corresponding targets holds promise for advancing our understanding of the mechanisms of virus infection and possible manipulation of these factors for developing durable virus resistance in crop plants.

Spatial relationship between pre-harvest hail and the impact from the wheat streak mosaic disease complex by using remote sensing data

Wheat streak mosaic (WSM) has long been considered the most serious disease of winter wheat in the Great Plains of America. The most effective control method of the WSM disease complex is to manage volunteer wheat that is often caused by the pre-harvest hailstorms in the Great Plains. A significant WSM disease outbreak over a large geographic area in western Nebraska, United States, in the 2017 wheat growing season was studied in relation to a pre-harvest hail in 2016 using open-data Landsat and Sentinel imagery and NOAA MRMS MESH hail data. Wheat growing areas were delineated and a WSM disease severity heat map was generated based on field NDRE readings from the satellite images. The spatial relationship between the hail event and WSM disease severity was demonstrated. For this extensive hail event, the impact from the WSM disease complex extended well beyond the area of impact from the pre-harvest hail. The dramatic extent of the virus impacts beyond the area of direct hail impact demonstrated in this study, strongly reinforces the need for community-wide attention to virus management in cases where large hail streaks occur at the optimum time for the development of pre-harvest hail (ca. within the 3 weeks before harvest). These findings not only agree with the assumption that the pre-harvest hail damaged wheat fields serve as the source fields of mites and virus, but also improves our understanding of the spatial pattern of virus spread which can benefit growers in making management decisions. The remote sensing methods used to delineate these findings proved valuable tools in studying this relationship.

Registration of ‘KS Big Bow’ hard white winter wheat

Abstract‘KS Big Bow’ (Reg. no. CV‐1206, PI 701521), a hard white winter wheat (Triticum aestivum L.) cultivar, was developed by the wheat breeding program at the Agricultural Research Center–Hays, Kansas State University, and released by the Kansas Agricultural Experiment Station in 2022. KS Big Bow was selected from a single cross of KS050223M‐2/KS11HW15 using a modified bulk breeding method. The main objective of this cross is to release a competitive hard white winter wheat cultivar with adaptation to the dryland production in western Kansas. KS Big Bow is an F5‐derived line and was tested in yield trials from 2017 to 2022 in Kansas before its release. It has performed well in dryland yield trials in western Kansas. KS Big Bow has a medium to medium‐early maturity and medium plant height. Its test weight and straw strength are good. KS Big Bow has a good disease‐resistant package including resistance to Wheat streak mosaic virus, moderate resistances to stripe rust (caused by Puccinia striiformis Westend. f. sp. tritici Erikss.) and stem rust (caused by P. graminis Pers f. sp. tritici Eriks. & E. Henn.), and intermediate resistance to Barley yellow dwarf virus. Its milling and baking qualities are about average.

Distribution of Wheat-Infecting Viruses and Genetic Variability of Wheat Streak Mosaic Virus and Barley Stripe Mosaic Virus in Kazakhstan.

Wheat is an essential cereal crop for the economy and food safety of Kazakhstan. In the present work, a screening of wheat and barley from different regions of Kazakhstan was conducted using newly developed specific primers for reverse transcription PCR and loop-mediated isothermal amplification (LAMP) assays. In total, 82 and 19 of 256 samples of wheat and barley tested positive for wheat streak mosaic virus (WSMV) and barley stripe mosaic virus (BSMV), respectively. A phylogenetic analysis using two independent methods revealed that most of the analyzed isolates had a European origin. Molecular data on the distribution and diversity of cereal viruses in Kazakhstan were obtained for the first time and will help lay a foundation for the implementation of genetics and genomics in wheat phyto-epidemiology in the country.

Зараженность вирусами желтой карликовости ячменя и полосатой мозаики пшеницы сортов озимой ржи (Secale cereale L.), выращиваемых на Среднем Урале

Rye is a strategically important crop in Russia, which is less demanding than other crops on soil fertility, mineral nutrition conditions and plant protection measures. Monitoring of the phytosanitary condition of winter rye varieties is a necessary measure for its stable yield. Four varieties of domestic selection Secale cereale L. (Nika, Vikras, Parom and Chusovaya), grown in the conditions of the Middle Urals in the experimental fields of the Perm and Ural Research Institute, PCR diagnostics of viral infections was carried out. RNA samples of 4 varieties of winter rye were analyzed by real-time PCR for infection with the Barley yellow dwart virus (BYDV) and the Wheat streak mosaic virus (VSMV). Barley yellow dwart virus was diagnosed in 60% of all studied samples of winter rye leaves, and wheat streak mosaic virus was diagnosed in 15% of the studied samples. The most resistant to the barley yellow dwart virus of barley leaves is the variety of winter rye Chusovaya, since it is infected only in the field of the Perm Research Institute. Varieties Nika 3, Vikras and Chusovaya are the most resistant to the wheat streak mosaic virus. A variety of winter rye was infected with this virus by Parom (30%). Further monitoring of the phytosanitary situation and profiling of viral infections of winter rye varieties in the territory of the Middle Urals is necessary.

Evaluation of Seed Transmission Rates of Wheat Streak Mosaic Virus in Mechanically Inoculated Winter and Spring Wheat Cultivars in Montana.

Wheat streak mosaic disease is caused by wheat streak mosaic virus (WSMV) and two other viruses and persistently limits wheat yields in the Great Plains region of the United States. Seed transmission of viruses is an important consideration in international movement and is important epidemiologically. Seed transmission of WSMV in wheat was first reported from Australia in 2005, but there is little data from United States cultivars on the rate of seed transmission. In 2018, mechanically inoculated winter and spring wheat cultivars were evaluated in Montana. We found differences in WSMV seed transmission rates between winter and spring wheat, with average transmission rates in spring wheat (3.1%) being five times higher compared to winter wheat (0.6%). Seed transmission rates in spring wheat were twice as high as the highest previously reported transmission rate for individual genotypes, 1.5%. The results from this study provide a strong argument for increasing the current testing of seed for breeding purposes prior to international movement when WSMV has been observed and caution against using grain from WSMV-infected fields as seed source because it can heighten the risk of wheat streak mosaic outbreaks.

Identifying Critical Regulators in the Viral Stress Response of Wheat (Triticum aestivum L.) Using Large-Scale Transcriptomics Data

Wheat (Triticum aestivum L.) cultivation has been globally restricted by many plant viruses such as the Wheat streak mosaic virus (WSMV), Barley stripe mosaic virus (BSMV), and Brome mosaic virus (BMV). Herein, the transcriptome of wheat was in silico analyzed under mono- (WSMV, BSMV, or BMV), bi- (BMV&BSMV, BMV&WSMV, and BSMV&WSMV), and tripartite (WSMV, BSMV, and BMV) infections using the RNA-seq technique. Total numbers of 1616/270, 5243/690 and 5589/2183 differentially expressed genes (DEGs) were up/down-regulated during the bipartite infection of BMV&BSMV, BMV&WSMV and BSMV&WSMV, respectively, while the tripartite infection resulted in the up/down-regulation of 6110/2424 DEGs. The NAC and bHLH were the most commonly presented transcription factor (TF) families in WSMV, BMV, and BSMV infection, while C2H2, bHLH, and NAC were the TF families involved in BMV&WSMV, BMV&BSMV, and BSMV&WSMV infections, respectively. The RLK-Pelle_DLSV was the most commonly expressed protein kinase (PK) family in all infection patterns. Promoter analysis showed that the motifs involved in gene expression, CUL4 RING ubiquitin ligase complex, stress response, brassinosteroid response, and energy-related pathways were significantly induced in wheat plants under bipartite infections. The gene expression network analysis showed that a defense-related gene, i.e., allene oxide synthase (AOS) gene, serves as a crucial hub in tripartite infections.

Molecular Characteristics of Barley Yellow Dwarf Virus-PAS-The Main Causal Agent of Barley Yellow Dwarf Disease in Poland.

Barley yellow dwarf is a threat to cereal crops worldwide. Barley yellow dwarf virus-PAS (BYDV-PAS) was detected for the first time in Poland in 2015, then in 2019. In the spring of 2021, in several locations in Poland, winter wheat and barley plants with dwarfism and leaf yellowing were collected. Reverse transcription-polymerase chain reaction results revealed BYDV presence in 47 samples and excluded wheat streak mosaic virus infections. Next, immuno-captured polymerase chain reactions confirmed only one case of co-infection caused by BYDV and wheat dwarf virus. Moreover, restriction fragment length polymorphism analysis showed that BYDV-PAS was predominant. The preliminary results were confirmed using sequencing. Infected cereal plants originated mainly from northwestern Poland. The complete coding sequence of coat protein (CP) and a fragment of RNA-dependent RNA polymerase (RdRp) genes of 14 Polish isolates were determined and deposited in the GenBank database. The nucleotide and deduced amino acid sequences of local isolates were compared with others reported to date, indicating their high similarity, from 75.4% to 99.5% and from 81.1% to 100% nucleotide sequence identity, in RdRp and CP, respectively. Phylogenetic analysis, based on the CP gene, revealed the presence of 3 main groups. The Polish isolates clustered together within the Ia group.

Seed Transmission of Wheat Streak Mosaic Virus and Triticum Mosaic Virus in Differentially Resistant Wheat Cultivars.

Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) are important viral pathogens of wheat in the Great Plains. These viruses individually or in mixed infections with High Plains wheat mosaic virus cause a devastating wheat streak mosaic (WSM) disease. Although seed transmission of WSMV has been studied, no information is currently available on that of TriMV. Furthermore, no study has explored the implications of mixed infections of WSMV and TriMV on seed transmission of one or both viruses. To study both aspects, seeds from differentially resistant field-grown wheat plants (cv. TAM 304 (susceptible), Joe (WSMV resistant, Wsm2 gene), and Breakthrough (BT) (WSMV and TriMV resistant, Wsm1 gene)) showing characteristic WSM symptoms were collected and analyzed to quantify both viruses using qRT-PCR. The percentage of seeds tested positive for WSMV or TriMV individually and in mixed infection varied with cultivar and virus combinations; 13% of TAM 304 seeds tested positive for WSMV, followed by 8% of BT and 4% of Joe seeds. Similarly, TriMV was detected in 12% of BT seeds, followed by 11% of TAM 304 and 8% of Joe seeds. Lastly, mixed infection was detected in 7% of TAM 304 seeds, followed by 4% in BT, and 2% in Joe. Dissection of field-collected seeds into three parts, embryo, endosperm, and seed coat, revealed both WSMV and TriMV accumulated only in the seed coat. Consistent with seeds, percent infection of WSMV or TriMV in the plants that emerged from infected seeds in each treatment varied with cultivar and virus combinations (WSMV: BT 3%; Joe 2%; TAM 304 9%; TriMV: BT 7%; Joe 8%; and TAM 304 10%). Plants infected with mixed viruses showed more pronounced WSM symptoms compared to individual infections. However, both viruses were present only in a few plants (BT: 2%, Joe: 1%, and TAM 304: 4%). Taken together, this study showed that TriMV was transmitted vertically at a higher frequency than WSMV in resistant cultivars, and the seed transmission of TriMV with WSMV increased the virulence of both pathogens (measured via WSM symptom severity) in the emerged plants. Furthermore, Wsm1 and Wsm2 genes considerably reduced WSMV transmission via infected seeds. However, no such effects were observed on TriMV, especially in progeny plants. These results reiterated the importance of planting clean seeds and highlighted the immediate need to identify/develop new sources of TriMV resistance to effectively manage the recurring WSM epidemic.

6K1, NIa-VPg, NIa-Pro, and CP of Wheat Streak Mosaic Virus are Collective Determinants of Wheat Streak Mosaic Disease in Wheat.

Wheat streak mosaic virus (WSMV; genus Tritimovirus; family Potyviridae) is the causal agent of the most economically important wheat streak mosaic disease of wheat (Triticum aestivum L.) in the Great Plains region of the USA. WSMV determinants responsible for wheat streak mosaic disease in wheat are unknown. Triticum mosaic virus (TriMV), a wheat-infecting virus, was used as an expression vector for the transient expression of each of the WSMV-encoded cistrons in wheat. WSMV-encoded 6K1, NIa-VPg, NIa-Pro, and CP cistrons in TriMV elicited symptoms specific to different stages of wheat streak mosaic disease without significantly affecting the genomic RNA accumulation. WSMV 6K1 produced early wheat streak mosaic disease-like symptoms of severe chlorotic streaks and patches. NIa-VPg and CP caused severe chlorotic streaks, followed by moderate stunting (only with NIa-VPg) of wheat, mimicking early- and mid-stage symptoms of wheat streak mosaic disease. WSMV NIa-Pro caused mild chlorotic streaks, followed by dark green leaves with severe stunting, representing the late symptoms of wheat streak mosaic disease. Collectively, these data suggest that cumulative effects of WSMV-encoded 6K1, NIa-VPg, NIa-Pro, and CP are responsible for different stages of wheat streak mosaic disease symptoms in wheat. Furthermore, deletion analysis of wheat streak mosaic disease determinants revealed that complete 6K1 and NIa-Pro, amino acids 3-60 and 121-197 of NIa-VPg, and amino acids 101-294 of CP are responsible for wheat streak mosaic disease-like symptoms in wheat. This study suggests that management strategies for wheat streak mosaic disease in wheat should target WSMV determinants of the disease phenotype.

OCCURRENCES OF WHEAT CURL MITE ACERIA TOSICHELLA KEIFER 1969 (ERIOPHYIDAE) AND THE ASSOCIATED VIRUSES, (WSMV, HPWMoV, TriMV) IN IRAQ

This study was aimed to investigate the significant wheat yield losses in northern and central Iraq. The cause of these losses was examining the presence of wheat curl mite Aceria tosichella and three viruses vectored by this species – Wheat streak mosaic virus (WSMV), High Plains wheat mosaic virus (HPWMoV), and Triticum mosaic virus (TriMV). Mite specimens were collected from Erbil, Mosul, and Baghdad over three years (2020-2022) and identified using morphological characterization and DNA sequencing of the ITS region. Virus presence was determined using Double Antibody Sandwich-Enzyme-Linked Immunosorbent Assay (DAS-ELISA). Mites were identified conclusively as A. tosichella, providing the first record of this species in Iraq. All three viruses were found to be present, with WSMV having the largest presence as it was detected in 99.56%, then HPWMoV (79.5%) of mite colonies. This is the first record of HPWMoV anywhere in Eurasia besides Ukraine and its widespread presence in Iraq in all three sampled provinces. TriMV was detected only in Erbil. To date this virus has been recorded only in North America and its limited presence in Iraq. The confirmed presence of A. tosichella and three vectored-viruses in Iraq are all new records and critical information for reducing wheat yield losses in this country.

Development of a Multiplex RT-PCR Assay for Simultaneous Detection of Ten Major Viral Pathogens of Wheat

Triticum mosaic virus (TriMV) and High plains virus (HPV), identified recently, have been considered among the major viruses that affect wheat. Carried by the same vector, wheat curl mite, both of these viruses cause yellowing and stunting of plants which are very similar to many other viruses attacking wheat. This makes it difficult to detect these viruses in different wheat lines, posing a major problem in the yield. This paper highlights the addition of these two viruses to a multiplex RT-PCR based method which already detected the presence of barley and cereal yellow dwarf viruses (B/CYDVs), soil-borne wheat mosaic virus (SBWMV), wheat spindle streak mosaic virus (WSSMV), and wheat streak mosaic virus (WSMV). The method uses specific sets of primers that detect the target viruses TriMV and HPV at 560 bp and 490 bp, respectively, in the presence of other distinct viruses such as B/CYDVs -PAV, -MAV, -SGV, -RPV, -RMV, WSSMV, SBWMV, and WSMV at 295, 175, 237, 400, 365, 154, 219, and 193 bp, respectively. The forward primer for each specific virus was fluorescently tagged to detect it in a higher throughput manner in capillary electrophoresis. All ten viruses may be viewed as peaks in an electropherogram from the capillary electrophoresis corresponding to their product sizes in base pairs. This advancement in the protocol allows detection of all ten wheat viruses in a single test, thus improving the diagnostic capability with only a slight increase in cost.