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Viruses belonging to genus Allexivirus infest garlic and are spread via propagation material and through a vector, the eriophyid mite Aceria tulipae (Keifer). The research material was garlic bulbs originating from Poland, available commercially on the Polish retail market. The aim of this study was to assess the possibility of transmission of Garlic virus B (GarV-B), Garlic virus C (GarV-C), Garlic virus D (GarV-D) and Garlic virus X (GarV-X) from garlic bulbs to leek plants by its vector, A. tulipae. These allexiviruses were detected in garlic bulbs and in leek leaves on which transferred mites fed. There was a high similarity of the genetic structure in the isolates of GarV-B, GarV-C, GarV-D and GarV-X collected from garlic bulbs and the isolates collected from the leek plants. The results of the study showed for the first time the potential of GarV-B, GarV-C, GarV-D and GarV-X to infect leek plants and constitutes the first attempt to examine the ability of A. tulipae to transmit these viruses from garlic to leeks. [ABSTRACT FROM AUTHOR]

High Plains wheat mosaic virus (HPWMoV, genus Emaravirus ; family Fimoviridae) , transmitted by the wheat curl mite ( Aceria tosichella Keifer), harbors a monocistronic octapartite single-stranded negative-sense RNA genome. In this study, putative proteins encoded by HPWMoV genomic RNAs 2–8 were screened for potential RNA silencing suppression activity by using a green fluorescent protein-based reporter agroinfiltration assay. We found that proteins encoded by RNAs 7 (P7) and 8 (P8) suppressed silencing induced by single- or double-stranded RNAs and efficiently suppressed the transitive pathway of RNA silencing. Additionally, a Wheat streak mosaic virus (WSMV, genus Tritimovirus ; family Potyviridae ) mutant lacking the suppressor of RNA silencing (ΔP1) but having either P7 or P8 from HPWMoV restored cell-to-cell and long-distance movement in wheat, thus indicating that P7 or P8 rescued silencing suppressor-deficient WSMV. Furthermore, HPWMoV P7 and P8 substantially enhanced the pathogenicity of Potato virus X in Nicotiana benthamiana . Collectively, these data demonstrate that the octapartite genome of HPWMoV encodes two suppressors of RNA silencing. [ABSTRACT FROM AUTHOR]

Soils are often complex habitats inhabited by a wide range of organisms, some harmful to plants and others beneficial, for example by attacking harmful organisms. Beneficial organisms include predatory mites, some of which have been commercialized for biological control of pest insects and mites. The objective of this work was to evaluate under laboratory condition the suitability of representative soil insect and mite pests, especially Aceria tulipae (Keifer), as prey to the soil-inhabiting predatory mites Proctolaelaps bickleyi (Bram) and Cosmolaelaps brevistilis (Karg). Predation, oviposition and survivorship of recently molted adult females of the predators were assessed in the dark in rearing chambers at 25 ± 1 °C and 75 ± 3% RH. Predation rate by P. bickleyi on A. tulipae was significantly higher than that by C. brevistilis (196.3 vs. 71.0 specimens/day). About 482 A. tulipae were preyed by each P. bickleyi at each day, when 500 A. tulipae were made available daily to the predator. Oviposition rate on that prey was also higher for P. bickleyi (4.2 eggs/day). For C. brevistilis, the highest level of oviposition was on Caliothrips phaseoli (Hood) (1.2 eggs/day). Survivorship was always higher for C. brevistilis (≥ 70%), given its ability to remain alive relatively long even in the absence of prey. High rates of survivorship of P. bickleyi were observed on A. tulipae, Bradysia matogrossensis (Lane) and Protorhabditis sp. Promising results were obtained for P. bickleyi on A. tulipae and even on other prey, justifying the conduction of complementary studies under field condition. [ABSTRACT FROM AUTHOR]

Dry bulb mite (DBM), Aceria tulipae, is an economically important mite with a worldwide distribution and a broad host range. As a generalist, it is the most important eriophyoid mite attacking bulbous plants such as garlic, onion and tulip. To date, DBM has been recorded on host plants belonging to the families Liliaceae, Amaryllidaceae, Melanthiaceae and Asparagaceae. However, a precise understanding of DBM host range is lacking as it is largely based on casual records of mites on plants, some of which may include accidental hosts. Moreover, the possible existence of cryptic species has not been considered. In this study the hypothesis that DBM may be a complex of distinct genetic lineages or cryptic species was tested by comparing the common barcode sequence marker mtDNA COI of specimens from several populations originating from the Netherlands and Poland. The population growth rate of DBM on seven agriculturally important plant species and on various parts of the garlic plant was also experimentally assessed in the laboratory. The results did not support the first hypothesis, and indicated that DBM populations originating from Poland and the Netherlands shared essentially the same genome. In addition, they indicated that DBM reached the highest population growth rate on leek and also displayed high growth rates on garlic, chive and red onion, whereas white onion and wheat were not colonized by the mites. Answering the question of whether DBM is a single polyphagous species rather than a complex of cryptic lineages is of particular importance since the misidentification of pests may lead to ineffective control strategies. Moreover, improved knowledge of DBM host range is essential for assessing risk to crops. [ABSTRACT FROM AUTHOR]

Viral diseases transmitted by wheat curl mite (WCM, Aceria tosichella Keifer) have been a persistent concern to farmers and researchers for at least six decades. Yield losses caused by mite–virus complexes up to 100% at the field level have been reported in several states of the Great Plains. This study was conducted to evaluate the level of resistance of hard winter wheat (Triticum aestivum L.) germplasm lines and to . Four sets of wheat lines from 2014 trials were screened, including 40 lines from the Northern Regional Performance Nursery, 40 lines from the Southern Regional Performance Nursery, 40 Texas elite wheat lines, and 52 and elite breeding lines. Two different mite collections, Texas WCM collection 1 (TWCMC1) and Texas WCM collection 2 (TWCMC2), were used to screen wheat lines. All cultivars and lines were infested with WCM at the two-leaf stage and scored on the first and second week after the second infestation. A total of 43 wheat lines and cultivars showed resistance to TWCMC1, but only 18 of them consistently exhibited resistance to TWCMC2, which is virulent to wheat-rye translocation 1AL.1RS. All the lines having the ‘Amigo’ 1AL.1RS translocation (Cmc3) across the four tests showed resistance to TWCMC1 but not to TWCMC2. Among the 22 lines with ‘TAM 112’ in their pedigree, 19 lines were resistant to TWCMC1, but only a subset of 12 showed resistance to TWCMC2. TWCMC2 and mite collections from Kansas and Nebraska were differentiated based on the high-resolution melting curves and sequence analysis of mite DNA. Results from this study will help wheat breeders and geneticists to select WCM-resistant parental lines for their breeding programs. [ABSTRACT FROM AUTHOR]

Wheat streak mosaic virus (WSMV), type member of the genus Tritimovirus in the family Potyviridae, is an economically important virus causing annual average yield losses of approximately 2 to 3% in winter wheat across the Great Plains. The wheat curl mite (WCM), Aceria tosichella, transmits WSMV along with two other viruses found throughout the Great Plains of the United States. Two common genotypes of WSMV (Sidney 81 and Type) in the United States share 97.6% nucleotide sequence identity but their transmission relationships with the WCM are unknown. The objective of this study was to determine transmission of these two isolates of WSMV by five WCM populations ('Nebraska', 'Montana', 'South Dakota', 'Type 1', and 'Type 2'). Nonviruliferous mites from each population were reared on wheat source plants mechanically inoculated with either Sidney 81 or Type WSMV isolates. For each source plant, individual mites were transferred to 10 separate test plants and virus transmission was determined by a double-antibody sandwich enzyme-linked immunosorbent assay. Source plants were replicated nine times for each treatment (90 individual mite transfers). Results indicate that three mite populations transmitted Sidney 81 at higher rates compared with Type. Two mite populations (Nebraska and Type 2) transmitted Sidney 81 and Type at higher rates compared with the other three populations. Results from this study demonstrate that interactions between virus isolates and mite populations influence the epidemiology of WSMV. [ABSTRACT FROM AUTHOR]

Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) are transmitted by the wheat curl mite (WCM, Aceria tosichella), and coinfections of wheat by these viruses are common in the field. Previous work has shown that mite genotypes vary in their ability to transmit TriMV. However, the degree to which coinfection of wheat modifies WCM vector competence has not been studied. The objective was to determine whether mite genotypes differed in virus transmission ability when feeding on wheat coinfected by WSMV and TriMV. First, WCM genotype type 2 was used to determine virus transmission rates from mock-, WSMV-, TriMV-, and coinfected wheat plants. Transmission rates were determined by using single-mite transfers from replicated source plants. Coinfection reduced WSMV transmission by type 2 WCM from 50 to 35.6%; however, coinfection increased TriMV transmission from 43.3 to 56.8%. Mite survival on single-mite transfer test plants indicates that the reduction in WSMV transmission may result from poor mite survival when TriMV is present. In a second study, two separate colonies of WCM genotype type 1 were tested to assess the impact of coinfection on transmission. Type 1 mites did not transmit TriMV from coinfected plants but the two colonies varied in transmission rates for WSMV (20.9 to 36.5%). Even though these changes in mite transmission rates are moderate, they help explain the high relative incidence of TriMV-positive plants that are coinfected with WSMV in field observations. These findings begin to demonstrate the complicated interactions found in this mite-virus complex. [ABSTRACT FROM AUTHOR]

Recent research on the wheat curl mite species complex has revealed extensive genetic diversity that has distinguished several genetic lineages infesting bread wheat (Triticum aestivum L.) and other cereals worldwide. Turkey is the historical region of wheat and barley (Hordeum vulgare L.) domestication and diversification. The close relationship between these grasses and the wheat curl mite provoked the question of the genetic diversity of the wheat curl mite in this region. The scope of the study was to investigate genetic differentiation within the wheat curl mite species complex on grasses in Turkey. Twenty-one wheat curl mite populations from 16 grass species from nine genera (Agropyron sp., Aegilops sp., Bromus sp., Elymus sp., Eremopyrum sp., Hordeum sp., Poa sp., Secale sp., and Triticum sp.) were sampled in eastern and southeastern Turkey for genetic analyses. Two molecular markers were amplified: the cytochrome oxidase subunit I coding region of mtDNA (COI) and the D2 region of 28S rDNA. Phylogenetic analyses revealed high genetic variation of the wheat curl mite in Turkey, primarily on Bromus and Hordeum spp., and exceptionally high diversity of populations associated with bread wheat. Three wheat-infesting wheat curl mite lineages known to occur on other continents of the world, including North and South America, Australia and Europe, were found in Turkey, and at least two new genetic lineages were discovered. These regions of Turkey exhibit rich wheat curl mite diversity on native grass species. The possible implications for further studies on the wheat curl mite are discussed. [ABSTRACT FROM AUTHOR]

Wheat is an important food grain worldwide and the primary dryland crop in the western Great Plains. A complex of three wheat curl mite (WCM)-transmitted viruses (Wheat streak mosaic virus, High plains virus, and Triticum mosaic virus [TriMV]) is a cause of serious loss in winter wheat production in the Great Plains. TriMV was first reported in Kansas in 2006 and later found in most other Great Plains states. Currently, three populations of WCM have been identified by genetic characterization and differential responses to mite resistance genes in wheat. In this study, we examined TriMV transmission by these three WCM populations: 'Nebraska' (NE), 'Montana' (MT), and 'South Dakota' (SD). Mite transmission using single-mite transfers revealed that the NE WCM population transmitted TriMV at 41%, while the MT and SD WCM populations failed to transmit TriMV. In multi-mite transfers, the NE WCM population transmitted TriMV at 100% level compared with 2.5% transmission by MT and SD WCM populations. Interestingly, NE mites transferred during the quiescent stages following the first and second instar transmitted TriMV at a 39 to 40% rate, suggesting that immature mites were able to acquire the virus and maintain it through molting. In addition, mite survival for single-mite transfers was significantly lower for NE mites when transferred from TriMV-inoculated source plants (60%) compared with mock-inoculated source plants (84%). This demonstrates potentially negative effects on WCM survival from TriMV. TriMV transmission differences demonstrated in this study underscore the importance of identification of mite genotypes for future studies with TriMV. [ABSTRACT FROM AUTHOR]

The dry bulb mite, Aceria tulipae, is the most important pest of stored tulip bulbs in The Netherlands. This tiny, eriophyoid mite hides in the narrow space between scales in the interior of the bulb. To achieve biological control of this hidden pest, candidate predators small enough to move in between the bulb scales are required. Earlier experiments have shown this potential for the phytoseiid mite, Neoseiulus cucumeris, but only after the bulbs were exposed to ethylene, a plant hormone that causes a slight increase in the distance between tulip bulb scales, just sufficient to allow this predator to reach the interior part of the bulb. Applying ethylene, however, is not an option in practice because it causes malformation of tulip flowers. In fact, to prevent this cosmetic damage, bulb growers ventilate rooms where tulip bulbs are stored, thereby removing ethylene produced by the bulbs (e.g. in response to mite or fungus infestation). Recently, studies on the role of predatory mites in controlling another eriophyoid mite on coconuts led to the discovery of an exceptionally small phytoseiid mite, Neoseiulus paspalivorus. This predator is able to move under the perianth of coconuts where coconut mites feed on meristematic tissue of the fruit. This discovery prompted us to test N. paspalivorus for its ability to control A. tulipae on tulip bulbs under storage conditions (ventilated rooms with bulbs in open boxes; 23 °C; storage period June-October). Using destructive sampling we monitored predator and prey populations in two series of replicated experiments, one at a high initial level of dry bulb mite infestation, late in the storage period, and another at a low initial dry bulb mite infestation, halfway the storage period. The first and the second series involved treatment with N. paspalivorus and a control experiment, but the second series had an additional treatment in which the predator N. cucumeris was released. Taking the two series of experiments together we found that N. paspalivorus controlled the populations of dry bulb mites both on the outer scale of the bulbs as well as in the interior part of the bulbs, whereas N. cucumeris significantly reduced the population of dry bulb mites on the outer scale, but not in the interior part of the bulb. Moreover, N. paspalivorus was found predominantly inside the bulb, whereas N. cucumeris was only found on the outer scale, thereby confirming our hypothesis that the small size of N. paspalivorus facilitates access to the interior of the bulbs. We argue that N. paspalivorus is a promising candidate for the biological control of dry bulb mites on tulip bulbs under storage conditions in the Netherlands. [ABSTRACT FROM AUTHOR]

Wheat streak mosaic virus (WSMV), Triticum mosaic virus, and Wheat mosaic virus, all vectored by the wheat curl mite Acería tosichella Keifer, frequently cause devastating losses to winter wheat production throughout the central and western Great Plains. Resistant 'Mace' and 'RonL are commercially available and contain the wsml and wsm2 genes, respectively, for resistance to WSMV. However, the resistance in these cultivars is temperature sensitive, ineffective above 27°C, and does not protect against the other common wheat viruses. The majority of winter wheat in the Southern Great Plains is planted in early fall as a dual-purpose crop for both grazing and grain production. Early plant-ing exposes wheat plants to warmer temperatures above the threshold for effective resistance. Studies were conducted to determine whether the resistance found in these cultivars would give infected plants the ability to recover as temperatures cooled to a range conducive to effec-tive genetic resistance. RonL, Mace, 'TAM 111', 'TAM 112', and 'Karl 92' wheat were infested with WSMV viruliferous mites at temperatures above the resistance threshold. After the initial 4-week infec-tion period, plants were subjected to progressively cooler temperatures during the winter months, well below the resistance threshold. Throughout the study, plant samples were taken to quantify virus titer and mite populations. Resistant RonL and Mace, which became se-verely infected during the initial infection period, were not able to recover even when temperatures dropped below the resistance thresh-old. However, TAM 112 showed resistance to WSMV but, more im-portantly, it also showed resistance to the wheat curl mite, because the mite population in this cultivar was significantly lower than on all other cultivars. The results of this study are significant in that they represent the first evidence of quantitative resistance to both WSMV and the wheat curl mite in a single wheat cultivar. Resistance to the wheat curl mite has potential to reduce losses to all mite-vectored virus diseases of wheat and not just WSMV. [ABSTRACT FROM AUTHOR]

Two economically important eriophyoid mites, Aceria tosichella (wheat curl mite; WCM) and Aceria tulipae (dry bulb mite; DBM), were frequently confounded in the world literature until the late 20th Century. Their morphological similarity and ambiguous data from plant-transfer and virus-transmission trials contributed to this confusion. Until recently, there was a general lack of knowledge about the existence of species complexes and it was not possible to accurately genotype tested mites. In the present study, two WCM genotypes of divergent host specificity ( MT-1 and MT-2) and one DBM genotype were tested for the acceptance of Poaceae, Amarylidaceae, and Liliaceae species that were reported or suspected as hosts of WCM or DBM. The MT-1 lineage colonized all tested plants. Onion- and garlic-associated DBM populations did not colonize tulip and wild garlic, suggesting that host-acceptance variability exists within A. tulipae s.l. Morphometric analysis did not discriminate closely-related MT-1 and MT-2 genotypes but completely separated both WCM genotypes from DBM based on the larger overall body size of the latter. Three morphological traits combined to discriminate between the DBM and MT-1 genotypes, both of which can infest Amarylidaceae bulbs. In total, these combined DNA sequence, host-acceptance, morphometrical results unambiguously separated two WCM and one DBM genotypes. Similar studies on additional lineages of both WCM and DBM should ultimately dispel previous taxonomic confusion between these two species. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 421-436. [ABSTRACT FROM AUTHOR]

The wheat curl mite (WCM) is microscopic, and therefore mite movement is difficult to track in the field. However, the virus complex it transmits causes observable and measurable changes to chlorophyll content and biomass. The ability to detect WCM (vectored viruses) with remote sensing was investigated by comparing vegetation indices calculated from proximal sensing data to ground-reference data obtained in the field. Of the 10 vegetation indices evaluated, the red-edge position (REP) provided the best relationship with virus symptoms observed in wheat. There was a significant and high correlation between REP and relative chlorophyll values and biomass and a significant, but lower, correlation between REP and percentage virus infection. [ABSTRACT FROM AUTHOR]

Field experiments were carried out with the goal of estimating the population fluctuations of the wheat curl mite,Aceria tulipaeKeifer, and its control. These experiments were conducted at an abandoned wheat field in Egypt during a growing season in 2012 in Cairo Governorate. Also, studies on life history aspects and reproductive parameters of the same species in the laboratory at 251 °C and 6015% R.H. were carried out. There were population fluctuations of the wheat curl mite,A. tulipae, when affected by temperature increase during the experimental season. The results showed that the population fluctuation continued at a moderate level until the end of February and then started to increase until it reached to three peaks from the mid of March to the mid of April when the temperature degrees were at 17–24 °C.A. tulipaeremoves cell contents of the leaves which generally become yellow. The obtained data indicated that the total developmental time of the immature stages was 8.90 ± 0. 74 and 9.58 ± 0.88 days for male and female, respectively, and the female fecundity was 22.8 eggs; 1.17 eggs/♀/day. Intrinsic rate of increase (rm) was found to be 0.153 individuals per female per day and the population multiplied 12.54 times in a generation time of 19.20 days under the given conditions. Three acaricides: Abamectin, Antimite and Sulphur were selected to control the wheat miteA. tulipae. The results of control pest experiments indicated that the Abamectin was superior in reducing the wheat miteA. tulipae(79% reduction) compared to Sulphur and Antimite which had approximately equal reductions (67 and 65% reductions, respectively). The study ended with the conclusion that the population of the wheat miteA. tulipaewas significantly highest at the interval from the mid of March to the mid of April. The wheat miteA. tulipaeis considered to be disastrous as its intrinsic rate of increase (rm) is high and the best control of this species at this interval was attained with Abamectin. [ABSTRACT FROM AUTHOR]

Aceria tosichella (the wheat curl mite, WCM) is a global pest of wheat and other cereals, causing losses by direct damage, as well as the transmission of plant viruses. The mite is considered to have an unusually wide host range for an eriophyoid species. The present study tested the commonly held assumption that WCM is a single, highly polyphagous species by assessing the host range of genetically distinct lineages of WCM occurring in Poland on different host plants. Genotyping was performed by analyzing nucleotide sequence data from fragments of the mitochondrial cytochrome c oxidase subunit I ( COI) and the nuclear D2 region of 28 S rDNA. Mean between-lineage distance estimated using COI data was found to be one order of magnitude greater than the within-clade lineage and, in some cases, comparable to distances between WCM lineages and a congeneric outgroup species. Host acceptance was tested by quantifying population growth for different WCM mitochondrial ( mt)DNA lineages when transferred from source host plants to test plants. These experiments revealed significant differences in host colonization ability between mt DNA lineages, ranging from highly polyphagous to more host-specific. The present study reveals that WCM is composed of several discrete genetic lineages with divergent host-acceptance and specificity traits. Genetic variation for host acceptance within A. tosichella s.l. may act as a reproductive barrier between these lineages, most of which had narrow host ranges. Two lineages appear to have high pest potential on cereals, whereas several others appear to specialize on wild grass species. We conclude that WCM is not a homogeneous species comprising polyphagous panmictic populations rather it is a complex of genetically distinct lineages with variable host ranges and therefore variable pest potential. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 165-180. [ABSTRACT FROM AUTHOR]

Abstract: The wheat curl mite (WCM) is a major pest in cereal crops around the world and the vector of at least four known pathogens capable of reducing yields in crops such as wheat, corn, barley, oats, millet and rye. Current taxonomy recognizes WCM as a single species, Aceria tosichella; however, recent genetic, physiological and ecological studies have shown that WCM is likely to be a species complex. In this study we assessed genetic variation and phylogenetic relationships among WCM from four continents and a wide range of host plants using DNA sequence data from one mitochondrial gene, one nuclear gene and a single nuclear intergenic spacer region. Phylogenetic analyses revealed 11 unique mite lineages associated with specific plant hosts including wheat and barley. Host associations were consistent across continents, often with a single haplotype dominating a host plant regardless of geographic origin. The genetic and ecological differences identified in this study support the notion that WCM is a species complex in need of major taxonomic revision. These findings have implications for control of WCM globally, particularly within the context of identifying plants that form ‘green bridge’ refuges, assessing disease transmission risk, and identifying resistance in cereal genotypes to WCM and associated pathogens. [Copyright &y& Elsevier]

Aceria tulipaeis one of the most damaging mite pests of garlic in the Gangetic Basin of West Bengal. The mite causes damage by infesting along the midrib of leaf. The leaves of infested plants are curled and twisted in a characteristic manner, and growth is stunted, causing 32% yield loss in this study under West Bengal conditions. The mite causes devastating damage to stored garlic also. Mite population initiated at the end of December and attained maximum numbers during mid-February. The garlic cultivar, Katki, was recorded as tolerant, whereas Goldana was susceptible to the mite attack. Ambient temperature and relative humidity were positively correlated with the mite population, whereas rainfall was correlated negatively. [ABSTRACT FROM PUBLISHER]

The wheat curl mite (WCM), Aceria tosichella, and the plant viruses it transmits represent an invasive mite-virus complex that has affected cereal crops worldwide. The main damage caused by WCM comes from its ability to transmit and spread multiple damaging viruses to cereal crops, with Wheat streak mosaic virus (WSMV) and Wheat mosaic virus (WMoV) being the most important. Although WCM and transmitted viruses have been of concern to cereal growers and researchers for at least six decades, they continue to represent a challenge. In older affected areas, for example in North America, this mite-virus complex still has significant economic impact. In Australia and South America, where this problem has only emerged in the last decade, it represents a new threat to winter cereal production. The difficulties encountered in making progress towards managing WCM and its transmitted viruses stem from the complexity of the pathosystem. The most effective methods for minimizing losses from WCM transmitted viruses in cereal crops have previously focused on cultural and plant resistance methods. This paper brings together information on biological and ecological aspects of WCM, including its taxonomic status, occurrence, host plant range, damage symptoms and economic impact. Information about the main viruses transmitted by WCM is also included and the epidemiological relationships involved in this vectored complex of viruses are also addressed. Management strategies that have been directed at this mite-virus complex are presented, including plant resistance, its history, difficulties and advances. Current research perspectives to address this invasive mite-virus complex and minimize cereal crop losses worldwide are also discussed. [ABSTRACT FROM AUTHOR]

Wheat curl mite (WCM)-transmitted viruses--namely, Wheat streak mosaic virus (WSMV), Triticum mosaic virus (TriMV), and the High Plains virus (HPV)--are three of the wheat-infecting viruses in the central Great Plains of the United States. TriMV is newly discovered and its prevalence and incidence are largely unknown. Field surveys were carried out in Colorado, Kansas, Nebraska, and South Dakota in spring and fall 2010 and 2011 to determine TriMV prevalence and incidence and the frequency of TriMV co-infection with WSMV or HPV in winter wheat. WSMV was the most prevalent and was detected in 83% of 185 season-counties (= s-counties), 73% of 420 season-fields (= s-fields), and 35% of 12,973 samples. TriMV was detected in 32, 6, and 6% of s-counties, s-fields, and samples, respectively. HPV was detected in 34, 15, and 4% of s-counties, s-fields, and samples, respectively. TriMV was detected in all four states. In all, 91% of TriMV-positive samples were co-infected with WSMV, whereas WSMV and HPV were mainly detected as single infections. The results from this study indicate that TriMV occurs in winter wheat predominantly as a double infection with WSMV, which will complicate breeding for resistance to WCM-transmitted viruses. [ABSTRACT FROM AUTHOR]

The wheat curl mite, Aceria tosichella Keifer, is an important pest in the western plains of the United States as well as in most major wheat-growing regions of the world. This mite is a vector of the economically important diseases wheat streak mosaic finis (WSMV), Triticum mosaic virus (TriMV), and High Plains virus (HPV). This study looked at seven accessions of Aegilops tauschii (Coss) Schmal to determine if they exhibit antibiosis, tolerance, and/or antixenosis to the wheat curl mite using 'Jagger', a known wheat curl mite-susceptible variety, and OK05312, a known wheat curl mite-resistant variety, as controls. Four of the seven tested accessions showed antibiotic effects on the population growth of wheat curl mite, as demonstrated by low number of wheat curl mite adults and nymphs at the end of the experiment. Three accessions and the commercial wheat variety Jagger showed some level of tolerance to wheat curl mite infestations, as demonstrated by a significantly reduced percentage proportional tissue dry weight and by tolerance index values. Four accessions demonstrated a strong antixenotic effect on the wheat curl mite, as demonstrated by significantly reduced numbers of mite adults at the end of the experiment. This study also established an effective method for determining antixenosis to the wheat curl mite in wheat that can be used for future experiments. All accessions demonstrated at least one type of plant resistance that could provide a genetic source for control of the wheat curl mite that may have the potential to be transferred into commercial wheat varieties. [ABSTRACT FROM AUTHOR]

The wheat curl mite, Aceria tosichella Keifer, transmits at least three harmful viruses, wheat streak mosaic virus (WSMV), high plains virus (HPV), and Triticum mosaic virus (TriMV) to wheat (Triticum aestivum L.) throughout the Great Plains. This virus complex is considered to be the most serious disease of winter wheat in the western Great Plains. One component of managing this disease has been developing mite resistance in wheat; however, identification of mite biotypes has complicated deployment and stability of resistance. This biotypic variability in mites and differential virus transmission by different mite populations underscores the need to better understand mite identity. However, A. tosichella has a history of serious taxonomic confusion, especially as it relates to A. tulipae Keifer, the dry bulb mite. Molecular techniques were used to genetically characterize multiple A. tosichella populations and compare them to populations of A. tulipae. DNA from these populations was polymerase chain reaction amplified and the ribosomal ITS2 region sequenced and compared. These results indicated limited variability between these two species, but two distinct types within A. tosichella were found that corresponded to previous work with Australian mite populations. Further work using sequencing of several mitochondrial DNA genes also demonstrated two distinct types of A. tosichella populations. Furthermore, the separation between these two A. tosichella types is comparable to their separation with A. tulipae, suggesting that species scale differences exist between these two types of A. tosichella. These genetic differences correspond to important biological differences between the types (e.g., biotypic and virus transmission differences). In light of these differences, it is important that future studies on biological response differences account for these mite differences. [ABSTRACT FROM AUTHOR]

Wild grasses, crops, and grassy weeds are known to host Wheat streak mosaic virus (WSMV) and its vector, the wheat curl mite (WCM). Their relative importance as a source of WSMV was evaluated. A survey of small-grain fields throughout Montana was conducted between 2008 and 2009. Cheatgrass was the most prevalent grassy weed and the most frequent viral host, with 6% infection by WSMV in 2008 (n = 125) and 15% in 2009 (n = 358). By mechanically inoculating plants with WSMV in the greenhouse, the highest susceptibility was found in rye brome (52.1%), jointed goatgrass (80.9%), and wild oat (53.9%). Quackgrass, not previously reported as a host, was susceptible to WSMV (12.7%). Mite transmission efficiency from susceptible grass species was lower than from wheat, and grass species must be a host for both WSMV and the WCM to serve as a virus source. WCM transmission was more efficient than mechanical transmission. Overall, results indicate that grass species can serve as a viral reservoir, regional variation in a weed species' susceptibility to WSMV cannot explain geographic variation in epidemic intensity, and crop species and closely related weeds (e.g., jointed goatgrass) remain the best reservoirs for both WSMV and the WCM. [ABSTRACT FROM AUTHOR]

Triticum mosaic virus (TriMV) is a recently discovered virus infecting wheat (Triticum aestivum) in the Great Plains region of the United States. it is transmitted by wheat curl mites (Aceria tosichella) which also transmit Wheat streak mosaic virus (WSMV) and Wheat mosaic virus. In a greenhouse study, winter wheat 'Millennium' (WSMV susceptible) and 'Mace' (WSMV resistant) were mechanically inoculated with TriMV, WSMV, TriMV+WSMV, or sterile water at the two-leaf growth stage. At 28 days after inoculation, final chlorophyll meter (soil plant analysis development [SPAD]) readings, area under the SPAD progress curve (AUSPC), the number of tillers per plant, shoot and root weight, and total nitrogen and carbon content were determined. In Millennium, all measured variables were significantly reduced by single or double virus infections, with the greatest reductions occurring in the double-infection treatment. In Mace, only final SPAD readings, AUSPC, and total nitrogen were significantly reduced by single or double virus infections. There was a significant (P ⩽ 0.05), positive linear relationship between SPAD readings and shoot weight in Millennium but not in Mace. The relationship between total nitrogen and shoot weight was positive, linear, and significant in both cultivars. The results from this study indicate that Mace, a WSMV-resistant cultivar, is also resistant to TriMV, and double infection of winter wheat by TriMV and WSMV exacerbates symptom expression and loss of biomass in susceptible cultivars. [ABSTRACT FROM AUTHOR]

The wheat curl mite (WCM), Aceria tosichella Keifer, is a polyphagous eriophyoid mite and the primary vector of wheat streak mosaic virus (WSMV) and five other viral pathogens in cereals. Previous research using molecular markers and a series of laboratory experiments found A. tosichella in Australia to consist of two genetically distinct lineages, which have broad overlapping distributions and differ in their ability to transmit WSMV under controlled conditions. This pattern of transmission also appears to be apparent in the field, whereby a strong association between WSMV detection and a single WCM lineage has been detected. In this study, we conduct a population genetic analysis and provide information on the genetic structure of the Australian viruliferous WCM lineage. We assessed genetic differentiation of 16 WCM populations using nine microsatellite markers. Strong evidence for extensive gene flow and low genetic structuring throughout the Australian wheatbelt was evident, with an exception for Western Australian and far north Queensland populations that appear to be genetically isolated. The data also indicate genetic patterns consistent with an arrhenotokous parthenogenetic mode of reproduction. Implications of these findings are discussed with reference to the management of WCM and associated cereal pathogens in Australia and overseas. [ABSTRACT FROM AUTHOR]

The majority of plant viruses are dependent on arthropod vectors for spread between plants. Wheat streak mosaic virus (family Potyviridae, genus Tritimovirus, WSMV) is transmitted by the wheat curl mite, Aceria tosichella Keifer, and this virus and vector cause extensive yield losses in most major wheat (Triticum aestivum L.)-growing regions of the world. Many cultivars in use are susceptible to this vector-virus complex, and yield losses of 10-99% have been documented, wheat curl mite resistance genes have been identified in goat grass, Aegilops tauschii (Coss) Schmal., and transferred to hexaploid wheat, but very few varieties contain effectively wheat curl mite resistance, due to virulent wheat curl mite populations. However, wheat curl mite resistance remains an effective strategy to reduce losses due to WSMV. The goal of our project was to identify the most effective, reproducible, and rapid method for assessing wheat curl mite resistance. We also wanted to determine whether mite resistance is affected by WSMV infection, because the pathogen and pest commonly occur together. Single and group wheat curl mite infestations produced similar amounts of leaf rolling and folding on wheat curl mite-susceptible wheat varieties that were independent of initial wheat curl mite infestation. This finding will allow accurate, efficient, large-scale screening of wheat germplasm for wheat curl mite resistance by infesting plants with sections of wheat leaf tissue containing mixed stages of wheat curl mite. The wheat curl mite-resistant breeding line 'OK05312' displayed antibiosis (reduced wheat curl mite population development). The effect of WSMV infection on wheat curl mite reproduction was genotype-dependent. Mite populations increased on infected wheat curl mite- and WSMV-susceptible plants compared with uninfected plants, but WSMV infection had no significant effect on wheat curl mite populations on resistant plants. OK05312 is a strong source of wheat curl mite resistance for wheat breeding programs. [ABSTRACT FROM AUTHOR]

The wheat curl mite (WCM), Aceria tosichella, is an eriophyid pest of cereals, and the vector responsible for the transmission of wheat streak mosaic virus (WSMV). In a previous study, the taxonomic status of A. tosichella in Australia was assessed using molecular markers. A. tosichella was shown to consist of two genetically distinct lineages likely to represent different species. Here we show that both lineages occupy similar distributions, occurring throughout the entire Australian wheat belt, and that the lineages are often found in sympatry. CLIMEX analysis suggests that tolerance to heat and desiccation limit the distribution of A. tosichella. In the laboratory, only one WCM lineage transmitted WSMV virus under controlled conditions. These results have implications for the management of WCM and WSMV within Australia. [ABSTRACT FROM AUTHOR]

The wheat curl mite (WCM), Aceria tosichella Keifer, is an eriophyoid pest of cereals, and the vector responsible for transmitting wheat streak mosaic virus. Several authors have suggested cryptic species of this mite identified through morphological variation, but this has never been conclusively demonstrated. Here, we use the mitochondrial 16S rRNA gene and two nuclear markers (internal transcribed spacer 1 and adenine nucleotide translocase) to show that WCM from Australia consists of at least two separate lineages that may represent putative species. In our study, both WCM variants were widespread and the only eriophyoids found on wheat varieties. The WCM variants were also found on alternate host plants, including some plants not known to host WCM. These results have implications for the control of this pest within Australian cereal crops. [ABSTRACT FROM AUTHOR]

Wheat streak mosaic virus (WSMV), vectored by the wheat curl mite Aceria tosichella, is one of the major limiting factors in wheat production in the Texas Panhandle. The mites are blown by wind into wheat fields from nearby volunteer wheat fields or fields supporting vegetation which harbor virulent mites. Consequently, gradients of wheat streak severity are often observed stretching from the edges of wheat fields into the center or beyond. To describe the magnitude of the spatial relationships between grain yield and wheat streak intensity across the field, studies were conducted in 2006 and 2007 in three infected fields. Wheat streak severity was quantified with reflectance measurements (remote sensing) at 555-nm wave length using a hand-held radiometer. Measurements were taken in several equally spaced 1 m² locations along a total of eight transects and grain yield was assessed from a 0.8 m² area of each location. State space analysis was used to describe the relationships in which yield data and reflectance values were used as dependent and explanatory variables, respectively. A structural time series model was formulated as a state space model where the unobserved components were modeled explicitly. In the analysis the state of yield at current location (d) was related to the state of wheat streak intensity either at current locations (d) or lagged locations with autoregressive values of the first order (d-1) or greater. There were significant cross-correlations between yield and wheat streak intensity up to distances of 150 m (P ≤ 0.05). Grain yield at the current position was significantly correlated with reflectance values at the same location and/or at lagged locations. The spatial aspects of the yield-reflectance relationships were best described by state space models with stochastic trends without slopes or deterministic trends with or without slopes. The models correctly predicted almost all of the observed yield values as a function of wheat streak intensity across the field within the 95% confidence interval. Results obtained in this study suggest that state space methodology can be a powerful tool in the study of plant disease spread as a function of other variables. [ABSTRACT FROM AUTHOR]

Triticum mosaic virus (TriMV) is a newly discovered virus found infecting wheat (Trificum aestivuni) in Kansas. This study was conducted to determine if the wheat curl mite (WCM, Aceria tosichella) and the bird cherry oat aphid (Rhopalosiphum padi) could transmit TriMV. Using different sources of WCM and two different isolates of TriMV, we were able to show the WCM is the vector of TriM V. Field analysis by enzyme-linked immunosorbent assay (ELISA) demonstrated natural infection patterns of wheat infected with TriMV, Wheat streak mosaic virus (WSMV), or both TriMV and WSMV, putatively infected by viruliferous WCM from a volunteer source growing adjacent to the wheat. Moreover, by single WCM transfers using WCM obtained from different wheat plants naturally infected with TriMV and WSMV and naturally infested with WCM, we showed that these WCM also transmitted TriMV only to wheat or transmitted both TriMV and WSMV to wheat. The infection rates of wheat with TriMV only using WCM transmission was low in both laboratory and field analyses. However, field analyses by ELISA showed that levels of infection of wheat by both TriMV and WSMV were high. No transmission of TriMV to wheat by R. padi occurred in our studies. [ABSTRACT FROM AUTHOR]

Substitutions in the amino-proximal region of wheat streak mosaic virus (WSMV) HC-Pro were evaluated for effects on transmission by the wheat curl mite ( Aceria tosichella Keifer). Alanine substitution at cysteine residues 16, 46 and 49 abolished vector transmission. Although alanine substitution at Cys20 had no effect, substitution with arginine reduced vector transmission efficiency. Random substitutions at other positions (Lys7 to Asn, Asn19 to Ile, and Arg45 to Lys) did not affect vector transmission. These results suggest that a zinc-finger-like motif (His13-X2-Cys16-X29-Cys46-X2-Cys49) in WSMV HC-Pro is essential for vector transmission. [ABSTRACT FROM AUTHOR]

The wheat curl mite (WCM), Aceria tosichella, the vector of Wheat streak mosaic virus (WSMV), often survives the summer on volunteer wheat (Triticum aestivum) and may disperse from this ‘green bridge’ in fall to newly planted winter wheat. Because some methods for managing volunteer wheat do not directly kill WCM, there is a window of risk for WCM and WSMV emigration after management has been applied. WCM survival in response to treatment of wheat by glyphosate, paraquat, stem cutting, and withholding water was measured in greenhouse experiments to determine how this window of risk for emigration varies with management. WCM populations on plants treated with paraquat or stem cutting decreased from the beginning of the sampling period. WCM populations on plants treated with glyphosate or that received no water increased up to 3 days after application and then decreased by 10 days after application. If glyphosate is used to manage volunteer wheat infested with WCM, it should be applied well before wheat is planted in fall. WCM in declining populations tended to be in an upright posture that could facilitate emigration via wind. The total green leaf area was strongly correlated with the number of WCM for treated plants and could be used in the field to predict the posttreatment survival of mites that pose a risk of emigration. [ABSTRACT FROM AUTHOR]

1. Theory predicts that plants that achieve fitness more through male function may be less tolerant of herbivory than those that achieve fitness through the female function. We tested this hypothesis by measuring the degree of infection and damage inflicted by the gall-forming eriophyid mite Aceria macrorhynchus on three different sexual morphs (males, protandrous bisexuals and protogynous bisexuals) of the Mediterranean tree Acer opalus. 2. The dependence of each morph on male function, estimated by registering gender changes over 5 years and quantifying male function, decreased in the order males, protandrous, protogynous. 3. The same decreasing order was found in the degree of gall infection produced by the mite, and in the reduction of photosynthetic rates and shoot growth, but not in the carbon-isotope discrimination caused by the mites. 4. Mites attack the morphs of A. opalus that rely more on the male function more often and more harmfully than they do other morphs. Male-biased herbivory is a selective force that could have been driving the separation of sexes in the genus Acer. Functional Ecology (2004) 18, 592–597 [ABSTRACT FROM AUTHOR]

Wheat streak mosaic virus (WSMV) (Family: Potyviridae; Genus: Tritimovirus), disseminated naturally by the wheat curl mite (Aceria tosichella Keifer), is an important disease of wheat (Triticum aestiyum L. em Thell.) worldwide. Breeding for resistant cultivars remains the best strategy to control the disease. Nine winter wheat genotypes with differential reaction to WSMV were crossed in a complete diallel mating design to determine the combining ability of WSMV resistance. Parents, F[sub 1], and reciprocal crosses were inoculated at the seedling (2-3 leaves) stage with a WSMV-SD isolate and evaluated for reaction under greenhouse conditions. Disease reaction was assessed twice (at 1-wk intervals) by a 1-to-5 scale (1 = no visible symptoms to light green streaks, 5 = severe yellow streaks and necrosis). Data were analyzed according to Griffing's Method 3 and Model 1, where one set of F[sub 1] and reciprocal F[sub 1] are included. Highly significant genotype effects (P < 0.01) were observed for WSMV resistance. General combining ability (GCA) and specific combining ability (SCA) effects for WSMV resistance were highly significant (P < 0.01), indicating that both additive and nonadditive genetic effects are involved in the inheritance of WSMV resistance. The reciprocal effects were not significant (P > 0.05). The ratio of combining ability variance components [(2σ[sup 2, sub GCA])/(2σ[sup 2, sub GCA] + σ[sup 2. SCA])] was small (0.1), indicating that nouadditive (i.e., dominance and epistasis) gene effects were more important than additive gene effects in controlling WSMV resistance in these crosses; therefore, progeny performance cannot be adequately predicted from GCA effects alone. [ABSTRACT FROM AUTHOR]

Wheat streak mosaic (WSM) is a serious viral disease of wheat (Triticum aestivum L.) that is vectored by the wheat curl mite (Aceria tosichella Keifer). Deployment of wheat cultivars with vector resistance is a possible method for WSM control. This 3-yr (1996-1997/ 1998-1999) field study compared by means of a split-plot design the effect of different sources of mite-resistance backcrossed into a common winter wheat genetic background on both the spread of WSM and on the resulting yield losses. The various lines were first seeded early (in July) in blocks of spaced plots to provide different disease source or spreader treatments as main plots. The same winter wheat lines were then seeded in mid-September into the spaces between the spreaders as subplot treatments to mimic the crop. Main-plot (spreader) treatments included the mite-susceptible winter wheat cultivars CDC Kestrel or Norstar, two mite-resistant backcross lines of Norstar with resistance from Thinopyrum ponticum (Podpera) Liu & Wang (Nst[sup *]5/Cmc2) and Triticum tauschii (Coss.) Schmal. (Nst[sup *]5/ Cmc1) plus oat (Avena sativa L.) as a nonhost. The two mite-resistant winter wheat lines, plus another mite-resistant backcross line with resistance from rye (Secale cereale L.) (Nst[sup *]5/1RS-1BL) and Norstar were also used as subplot treatments. The presence of vector resistance in the spreader treatments reduced the intensity of disease symptoms in the spreader rows themselves and increased their grain yield. In 2 of 3 yr, these yield differences were dramatic. Resistance in the spreader also reduced the secondary spread of WSM into the adjacent winter wheat subplots with conventional planting dates. During severe outbreaks of WSM, (1996-1997 and 1997-1998), Nst[sup *]5/Cmc2 was more effective with a lower frequency of severely infected plants and smaller yield losses than Nst[sup *]5/Cmc1 or Nst[sup *]5/1RS-1BL. In conclusion, control of WSM through vector resistance requires an effective resistance gene in both thc spreader and the crop. [ABSTRACT FROM AUTHOR]

The wheat curl mite (WCM), Aceria tosichella Keifer, is the vector of wheat streak mosaic virus and high plains virus which cause significant crop loss in winter wheat throughout the western Great Plains. Volunteer wheat emerging before harvest, as a result of severe hail, is the primary source of mites and virus that infect fall-planted winter wheat. Wind-borne movement of the WCM is of key importance in the spread and infection of the virus complex. Significant movement of WCM from wheat has been thought to be closely tied to the senescence or deterioration of the host. Results from field and greenhouse studies indicated that movement from un- vernalized winter wheat was not closely associated with the deterioration of the wheat host. Greenhouse studies showed no correlation between WCM movement and plant condition, but there was a highly significant relationship between WCM movement and mite population on the host plant. Field studies did not demonstrate increased movement associated with deteriorating un-vernalized winter wheat. However, healthier hosts which were able to support a larger population of mites were associated with increased movement. The main influence on the level of mite movement relates to the size of the source population and not the condition of the host plant, but plant condition appears to be a factor in limiting the increase of the WCM population. [ABSTRACT FROM AUTHOR]

Deals with a study which evaluated the resistance of Aegilops tauschii, the wild diploid D-genome progenitor of wheat, Triticum aestivum, to biotypes of the wheat curl mite, Aceria tosichella. Background to the study; Materials and methods; Results and discussion.

To diversify the genetic base of resistance in wheat (Triticum aestivum L.) to the wheat curl mite (WCM), Aceria tosichella Keller, resistance to this pest was transferred from the dipolid goatgrass Aegilops taushcii (Coss.). Schmal. to the hard red winter wheat germplasm KS96WGRC40 by backcrossing to the cultivar TAM 107. KS96WGRC40 has WCM resistance derived from both Ae. tauschii and rye (Secale cereale L.). The objectives of this study were to determine if a unique WCM resistance gene was transferred from Ae. tauschii to KS96WGRC40 and to determine the chromosome and linkage map locations of the WCM resistance genes in the germplasm. The rye-derived WCM resistance gene in TAM 107 and KS96WGRC40, designated Cmc3, is present on wheat-rye translocation T1AL·1RS. Marker analysis of a segregating F[sub 2] population revealed that the rye-specific microsatellite marker SCM09 can be used to select wheat lines carrying the 1RS segment and Cmc3. Allelism tests indicated that the Ae. tauschii-derived WCM resistance gene in KS96WGRC40, designated Cmc4, segregated independently of the Cmc1 gene previously transferred from this species. Molecular and cytogenetic analyses located Cmc4 distally on chromosome 6DS flanked by markers Xgdm141 (4.1 centimorgans, cM) and XksuG8 (6.4 cM). The linked markers may be used in wheat breeding programs for the selection of lines resistant to WCM and for gene pyramiding. [ABSTRACT FROM AUTHOR]

Presents information on a study that examined the genomic composition of the Zhong series of partial amphiploids for wheat streak mosaic virus and wheat curl mite resistance. Review of related literature; Materials and methods used; Results and discussion.

Evaluates the effectiveness of resistance in wheat to wheat curl mite (WCM) collected from various locations in the Great Plains. Limiting of wheat yield by wheat streak mosaic virus which is vectored by WCM; Lines and their sources of resistance; Need for testing of mites for their response to resistance genes in breeding programs before resistant cultivars are deployed in the field.

Focuses on the infection of Lolium perenne and L. multiflorum by Aceria tulipae in Wales. Leaf curling; Trapped leaf syndrome; Electron microscopy of the plant.