Barley Yellow Dwarf Research Articles

Coordination of Diagnostic Efforts in the Great Plains: Wheat Virus Survey and Modeling of Disease Onset.

Following the discovery of two new wheat virus diseases in the United States, the Great Plains region (Colorado, Kansas, Montana, Nebraska, North Dakota, Oklahoma, South Dakota, Texas, and Wyoming) of the National Plant Diagnostic Network (NPDN) initiated a project to measure the prevalence of five wheat diseases using indirect ELISA. Wheat streak mosaic virus (WSMV), Wheat mosaic virus (WMoV), and Triticum mosaic virus (TriMV) were found in all nine states. WSMV was the most prevalent, averaging 23 to 47% of samples each year. TriMV and WMoV were detected with WSMV (in up to 76% of the samples). All three mite-transmitted viruses were present in 26% or fewer of the samples. Aphid-transmitted viruses in the barley yellow dwarf complex Barley yellow dwarf virus, and Cereal yellow dwarf virus-RPV were less frequent (fewer than 65% of the samples). This paper presents the first case-control methodology paper using plant diagnostic laboratory data and the first signed diagnostic data-sharing agreement between the NPDN and its regulatory stakeholders. Samples collected when <700 cumulative degree-days base 0°C, were twice as likely to be virus negative. This proof-of-concept effort highlights the potential of the NPDN and its National Data Repository to develop knowledge about emerging diseases.

Eukaryotic translation initiation factor eIF4G utilizes different domains to coordinate with eIF4A, eIF4B and eIF4E in binding 3′ Cap‐independent translation element of Barley Yellow Dwarf Virus

Barley Yellow Dwarf Virus (BYDV) lacks a 5′ (7‐methyl guanosine) cap as well as a 3′poly A tail. Like many plant viruses, BYDV contains a cap independent translation element (CITE) in the 3′ untranslated region of the viral mRNA. BTE (Barley Yellow Dwarf Virus like cap‐independent element) is one of the well characterized CITEs. BTE mediated translation primarily depends on eukaryotic initiation factor eIF4G. BTE binds to eIF4G; however, the details of BTE initiated translation are still unclear. Three eIF4G deletion mutants with different domain organization were used to investigate BTE interaction with eIF4G: eIF4G601‐1196 is the eIF4G truncated fragment containing amino acids from 601 to 1196, including eIF4E, central eIF4A, eIF4B binding domains and the possible BTE binding region; eIF4G601‐1488 is a longer fragment with one additional C‐terminal eIF4A binding domain; eIF4G742‐1196 is a shorter deletion mutant lacking the eIF4E binding sequence. eIF4G601‐1196 binds BTE as efficiently as wild type eIF4G and supports translation. Translation initiation factor eIF4A and eIF4B with ATP (helicase complex) stimulate eIF4G601‐1196 binding with BTE but not eIF4G601‐1488, suggesting that the helicase complex function relies on the eIF4G central eIF4A binding domain, not the C‐terminal eIF4A binding domain. eIF4E, upon binding with eIF4G mutants which have eIF4E binding region, significantly increases the binding to BTE. These data suggest eIF4E has a significant role in eIF4G‐RNA binding even in the absence of the cap structure.Support or Funding InformationNSF MCB 1513737

Identification of genes conferring resistance to viral diseases of barley using multiplex PCR

This paper describes a rapid and cost-effective assay for identifying economically important barley resistance genes based on multiplex PCR. A newly created reaction mixture is used for detecting the resistance genes rym4, rym5, rym11-b and Ryd2 conferring resistance to barley yellow mosaic viruses and Barley yellow dwarf virus (BYDV). It is possible to identify all these genes using only a single PCR reaction without the necessity for subsequent cutting with restriction endonucleases. This is important for developing resistant barley genotypes inasmuch as it can increase work productivity and reduce costs.

Virus infection mediates the effects of elevated CO2 on plants and vectors

Atmospheric carbon dioxide (CO2) concentration has increased significantly and is projected to double by 2100. To increase current food production levels, understanding how pests and diseases respond to future climate driven by increasing CO2 is imperative. We investigated the effects of elevated CO2 (eCO2) on the interactions among wheat (cv. Yitpi), Barley yellow dwarf virus and an important pest and virus vector, the bird cherry-oat aphid (Rhopalosiphum padi), by examining aphid life history, feeding behavior and plant physiology and biochemistry. Our results showed for the first time that virus infection can mediate effects of eCO2 on plants and pathogen vectors. Changes in plant N concentration influenced aphid life history and behavior, and N concentration was affected by virus infection under eCO2. We observed a reduction in aphid population size and increased feeding damage on noninfected plants under eCO2 but no changes to population and feeding on virus-infected plants irrespective of CO2 treatment. We expect potentially lower future aphid populations on noninfected plants but no change or increased aphid populations on virus-infected plants therefore subsequent virus spread. Our findings underscore the complexity of interactions between plants, insects and viruses under future climate with implications for plant disease epidemiology and crop production.

Cloning of eight Rhopalosiphum padi (Hemiptera: Aphididae) nAChR subunit genes and mutation detection of the β1 subunit in field samples from China

The bird cherry-oat aphid, Rhopalosiphum padi (L.), is one of the most important wheat pests. This aphid damages through direct feeding and by transmitting the Barley yellow dwarf virus (BYDV). Both types of damage significantly reduce the quality and yield of wheat crops globally. Insecticides are the primary method of controlling the bird cherry-oat aphid in China, yet this aphid species has developed resistance to different types of insecticides, especially organophosphates and carbamates. In the last decade, control of R. padi depends primarily on the spray of neonicotinoid insecticides, however, research on the resistance of R. padi to neonicotinoids has been limited. In this study, the full lengths of seven α-subunit (Rpα1, Rpα2, Rpα3, Rpα4, Rpα5, Rpα7-1, and Rpα7-2) and one β-subunit (Rpβ1) genes from R. padi were obtained with RT-PCR and RACE techniques. Sequence analysis showed that these genes had all the characteristics of the nAChR gene family and were highly homologous with the reported nAChR genes from other insects, and alternative splicing was detected in Rpα3 and Rpα5 subunits. Analysis of the cDNA sequence of the extracellular region of the nicotinic acetylcholine receptor β1 subunit gene from 120 R. padi field samples collected in 11 Provinces revealed 17 single nucleotides polymorphism (SNP) sites, of which seven were amino acid polymorphism sites (V53I, V53G, N54T, A60T, F61L, W79C, and V83I) and two were in the loop D region (W79C and V83I). The current study will facilitate further studies on the molecular mechanisms of targeted resistance of the aphid to neonicotinoid insecticides.

Noncoding RNAs of Plant Viruses and Viroids: Sponges of Host Translation and RNA Interference Machinery.

Noncoding sequences in plant viral genomes are well-known to control viral replication and gene expression in cis. However, plant viral and viroid noncoding (nc)RNA sequences can also regulate gene expression acting in trans, often acting like 'sponges' that bind and sequester host cellular machinery to favor viral infection. Noncoding sequences of small subgenomic (sg)RNAs of Barley yellow dwarf virus (BYDV) and Red clover necrotic mosaic virus (RCNMV) contain a cap-independent translation element that binds translation initiation factor eIF4G. We provide new evidence that a sgRNA of BYDV can globally attenuate host translation, probably by sponging eIF4G. Subgenomic ncRNA of RCNMV is generated via 5' to 3' degradation by a host exonuclease. The similar noncoding subgenomic flavivirus (sf)RNA, inhibits the innate immune response, enhancing viral pathogenesis. Cauliflower mosaic virus transcribes massive amounts of a 600-nt ncRNA, which is processed into small RNAs that overwhelm the host's RNA interference (RNAi) system. Viroids use the host RNAi machinery to generate viroid-derived ncRNAs that inhibit expression of host defense genes by mimicking a microRNA. More examples of plant viral and viroid ncRNAs are likely to be discovered, revealing fascinating new weaponry in the host-virus arms race.

Brachypodium distachyon is a suitable host plant for study of Barley yellow dwarf virus.

Barley yellow dwarf viruses (BYDVs) belong to the family Luteoviridae and cause disease in cereals. Because of the large and complex genome of cereal plants, it is difficult to study host-virus interactions. In order to establish a model host system for the studies on BYDVs, we examined the susceptibility of a monocot model plant, Brachypodium distachyon, to BYDV-GAV infection. Fourteen days after BYDV-GAV inoculation by aphid transmission, B. distachyon plants (inbred line Bd21-3) showed conspicuous disease symptoms such as leaf reddening, dwarfness and root stunting. Virus accumulation was detected in both shoots and roots using reverse transcription PCR and triple antibody sandwich ELISA. Compared with infected wheat plants, B. distachyon plants developed more severe disease symptoms and accumulated a higher level of BYDV-GAV. Under transmission electron microscope, we observed that virus particles accumulated in companion cells and BYDV-GAV infection was associated with the deformation of chloroplasts in the infected leaves of B. distachyon plants. Our results suggest that B. distachyon is a suitable and promising experimental model plant for the host-BYDV-GAV pathosystem and possibly for other BYDVs.

Occurrence of Winter Cereal Viruses in New South Wales, Australia, 2006 to 2014.

Winter cereal viruses can cause significant crop losses; however, detailed knowledge of their occurrence in New South Wales, Australia is very limited. This paper reports on the occurrence of Wheat streak mosaic virus (WSMV), Wheat mosaic virus (WMoV), Barley yellow dwarf virus (BYDV), Cereal yellow dwarf virus (CYDV), and their serotypes between 2006 and 2014. Detection of WMoV is confirmed in eastern Australia for the first time. The BYDV and CYDV 2014 epidemic is examined in detail using 139 samples of wheat, barley, and oat surveyed from southern New South Wales. The presence of virus was determined using enzyme-linked immunosorbent assays. The results reveal a high frequency of the serotype Barley yellow dwarf virus - MAV as a single infection present in 27% of samples relative to Barley yellow dwarf virus - PAV in 19% and CYDV in 14%. Clear differences emerged in the infection of different winter cereal species by serotypes of BYDV and CYDV. These results are contrasted to other Australian and international studies.

Management Strategies for Barley Yellow Dwarf on Winter Wheat in Kansas

Barley yellow dwarf (BYD) is one of the most important wheat diseases in the state of Kansas. Several methods of disease management have been recommended to mitigate losses from BYD including the use of seed-treatment insecticides, delayed planting of winter wheat, and deploying cultivars with resistance to BYD. The goal of this research was to quantify the impact of these three management strategies, alone and in combination, on BYD disease progress and grain yields in Kansas. When field experiments were averaged over four years, treating seed with the insecticide imidacloprid (Gaucho) reduced the daily increase in the area under the disease progress curve (AUDPC) by 35.0% and corresponding yield losses from BYD by 16.4%. Compared with early planting, late planting reduced AUDPC by 47.9% and corresponding yield losses by 57.5%. Planting a moderately resistant cultivar reduced AUDPC by 80.9% and corresponding yield losses by 72.6% compared with a susceptible cultivar. When all three BYD management methods were combined, BYD was reduced by 95.2% and yield losses reduced by 97.1% when compared with not using any of the management methods. Therefore, integrating management practices can result in high levels of control of BYD in Kansas. Accepted for publication 4 May 2016. Published 7 June 2016.

Survey of Barley yellow dwarf virus incidence in winter cereal crops, and assessment of wheat and barley resistance to the virus

A survey of Barley yellow dwarf virus (BYDV) incidence in cereal crops in the Czech Republic over 4 years showed, on average, 13.3% BYDV-positive, randomly tested wheat and barley samples. The cultivated wheat and barley cultivars had different levels of susceptibility to BYDV infection. Field trials were performed with different barley and wheat breeding lines and cultivars, and resistance traits were evaluated after artificial inculcation by the viruliferous aphid vector Rhopalosiphum padi L. with BYDV-PAV. Our results showed high variability of visual symptom score (VSS) and reduction in grain weight per spike (GWS-R) in trials within the tested lines and cultivars. The barley line (WBON 96-123) and cultivars (Wysor, Travira) that contained RYd2 differed significantly from other cultivars in VSS. Line WBON 96-123 and cvv. Wysor and Yatzi showed the lowest GWS-R. Wheat line PSR 3628 and cvv. Altigo, Elan, Sparta, Aladin and Hewit showed significant difference from other cultivars in VSS. PSR 3628, Sparta, and Elan showed the lowest GWS-R. Similar results were obtained from BYDV titre analysis by RT-qPCR corresponding to the VSS and GWS-R traits. A low virus titre corresponded to low VSS and GWS-R. Hence, our results suggest that laborious and time-consuming GWS-R analysis could be replaced in some cases by qPCR-based BYDV titre analysis and, together with VSS evaluation, could enhance the efficiency of resistance assessment.

Interactions between Metopolophium festucae cerealium (Hemiptera: Aphididae) and Barley yellow dwarf virus (BYDV-PAV).

Interactions between an invasive aphid, Metopolophium festucae (Theobald) subsp. cerealium, and Barley yellow dwarf virus (BYDV-PAV) were studied under laboratory conditions. M. festucae cerealium is an economic pest of wheat and barley that has recently been found in high population densities in wheat in the Pacific Northwest of the United States. BYDV-PAV is the most prevalent and injurious species of BYDV worldwide and in the Pacific Northwest. Although M. festucae sensu stricto (Theobald 1917) has been reported previously as a vector of some BYDV isolates, there is no confirmed transmission of BYDV by M. festucae cerealium. Two experiments examined the ability of M. festucae cerealium to transmit BYDV-PAV. The first used single aphids caged to indicator plants of a BYDV-susceptible winter wheat cultivar and the second used multiple aphids on each test plant. M. festucae cerealium did not transmit BYDV-PAV in either experiment, whereas transmission by a known BYDV vector, Rhopalosiphum padi L., was consistently high (≥93%). A third experiment compared the intrinsic growth rate, days until first reproduction and daily reproduction by M. festucae cerealium on sham-inoculated and BYDV-PAV-infected wheat, but detected no differences. The findings are reviewed in light published data on M. festucae species, BYDV transmission, and the potential pest status of this new invading aphid.

Within-Host Niche Differences and Fitness Trade-offs Promote Coexistence of Plant Viruses.

Pathogens live in diverse, competitive communities, yet the processes that maintain pathogen diversity remain elusive. Here, we use a species-rich, well-studied plant virus system, the barley yellow dwarf viruses, to examine the mechanisms that regulate pathogen diversity. We empirically parameterized models of three viruses, their two aphid vectors, and one perennial grass host. We found that high densities of both aphids maximized virus diversity and that competition limited the coexistence of two closely related viruses. Even limited ability to simultaneously infect (coinfect) host individuals strongly promoted virus coexistence; preventing coinfection led to priority effects. Coinfection generated stabilizing niche differences by allowing viruses to share hosts. However, coexistence also required trade-offs between vector generalist and specialist life-history strategies. Our predicted outcomes broadly concur with previous field observations. These results show how competition within individual hosts and vectors may lead to unexpected population-level outcomes between pathogens, including coexistence, competitive exclusion, and priority effects, and how contemporary coexistence theory can help to predict these outcomes.

The effect of elevated CO2 and virus infection on the primary metabolism of wheat.

Atmospheric CO2 concentrations are predicted to double by the end of this century. Although the effects of CO2 fertilisation in crop systems have been well studied, little is known about the specific interactions among plants, pests and pathogens under a changing climate. This growth chamber study focuses on the interactions among Barley yellow dwarf virus (BYDV), its aphid vector (Rhopalosiphum padi) and wheat (Triticum aestivum L. cv. Yitpi) under ambient (aCO2; 400µmolmol-1) or elevated (eCO2; 650µmolmol-1) CO2 concentrations. eCO2 increased the tiller number and biomass of uninoculated plants and advanced the yellowing symptoms of infected plants. Total foliar C content (percentage of the total DW) increased with eCO2 and with sham inoculation (exposed to early herbivory), whereas total N content decreased with eCO2. Liquid chromatography-mass spectrometry approaches were used to quantify the products of primary plant metabolism. eCO2 significantly increased sugars (fructose, mannitol and trehalose), irrespective of disease status, whereas virus infection significantly increased the amino acids essential to aphid diet (histidine, lysine, phenylalanine and tryptophan) irrespective of CO2 concentration. Citric acid was reduced by both eCO2 and virus infection. Both the potential positive and negative biochemical impacts on wheat, aphid and BYDV interactions are discussed.

高压静电场对小麦叶片保护酶系统及麦长管蚜种群动态的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 高压静电场对小麦叶片保护酶系统及麦长管蚜种群动态的影响 DOI: 10.5846/stxb201407041377 作者: 作者单位: 西北农林科技大学植物保护学院,西北农林科技大学植物保护学院,西北农林科技大学植物保护学院,西北农林科技大学植物保护学院,西北农林科技大学植物保护学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(39970112,30470268);高等学校博士学科点专项科研基金(20130204110004) Effects of high voltage electrostatic fields on protective enzyme activity in wheat plants and on the population dynamics of Sitobion avenae fabricius (hemiptera:aphididae) Author: Affiliation: College of Plant Protection, Northwest A & F University,College of Plant Protection, Northwest A DdDd F University,College of Plant Protection, Northwest A DdDd F University,College of Plant Protection, Northwest A & F University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为明确高压静电场胁迫小麦种子对其叶片以及麦长管蚜Sitobion avenae Fabricius产生的影响。测定了小麦苗期叶片及麦长管蚜体内抗氧化酶(SOD, POD, CAT)的活性,并采用盆栽种群实验研究了麦长管蚜的种群动态。实验结果表明:(1)在未被麦长管蚜取食的小麦叶片中,SOD和POD活性最大值均出现于4 kV/cm处理组,且与对照组差异显著(P < 0.05),CAT活性在未被取食的叶片中无显著差异(P > 0.05);而被取食过的叶片中,4 kV/cm处理组的SOD和POD活性均显著低于对照组(P < 0.05),而CAT活性结果显示4 kV/cm和6 kV/cm处理组均显著低于对照组(P < 0.05)。(2)静电场处理组中麦长管蚜的SOD和CAT活性均显著高于对照组(P < 0.05),但POD活性均显著低于对照组(P < 0.05)。(3)种群动态和逻辑斯蒂模型参数显示4 kV/cm处理组的小麦环境容纳量(K)最小。研究的创新点在于对影响麦长管蚜的介质(小麦)的抗氧化酶活性进行了测定,进一步明确了高压静电场对动植物的影响,说明了4 kV/cm是影响小麦和麦长管蚜的关键强度,为高压静电生态控蚜提供了新思路。 Abstract:Sitobion avenae (Fabricius) (Homoptera: Aphididae) is one of the most common pests of wheat. It damages plants by ingesting sap from ears, stems, leaves, and other tender plant parts. It is also known to transmit viruses (e.g., barley yellow dwarf virus) during feeding, thereby reducing wheat yield and quality. High voltage electrostatic fields (HVEF) are reported to influence a wide variety of biological and physical systems. For example, reports of several studies state that HVEF affected plant physiology such that the sprout rates of seeds were improved. Moreover, in agrophysics, electrostatic charging has been used to improve targeting and efficacy of agricultural sprays. Organisms showing aerobic metabolism face constant risk from reactive oxygen species (ROS), such as the superoxide radical (·O-2), hydroxyl radical (OH·) and hydrogen peroxide (H2O2). The function of protective enzymes includes avoidance of unwanted cellular cytotoxicity and oxidative damage by regulating the production of ROS. In order to explore the effects of HVEF on S. avenae and wheat plants, activities of protective (i.e., anti-oxidative) enzymes such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were examined in wheat leaves and aphid individuals. To evaluate the impact of HVEF on the aphids more accurately, the population dynamics of S. avenae was also investigated. The results showed that the activities of anti-oxidative enzymes were affected by HVEF in both plants and aphids. In undamaged leaves, higher SOD and POD enzyme activities were observed after 4 kV/cm treatment, compared to the control group (P < 0.05), but the CAT activities showed no significant change (P > 0.05). In damaged leaves, SOD and POD activities of 4 kV/cm treatment were significantly lower than those of the control (P < 0.05). CAT activity for treatments with 4 kV/cm and 6 kV/cm were significantly lower than those of the control (P < 0.05). When compared with the control, SOD and CAT activities of S. avenae in all the treatment groups were significantly higher (P < 0.05), while POD activities were significantly lower (P < 0.05). The population dynamics and logistic model parameters showed that the 4 kV/cm treatment resulted in the lowest carrying capacity for S. avenae. Therefore, it is reasonable to conclude that 4 kV/cm is the key intensity for wheat and wheat aphids. In this research, the effects of HVEF on anti-oxidative enzyme activities in wheat were evaluated, and its impact on both animal and plant was further clarified. As is well known, chemical control is often used within an Integrated Pest Management (IPM) program in order to keep pest numbers below the economic threshold. However, farmers often blindly increase the quantity and frequency of insecticide usage to prevent pest damage. Our research showed that seed treatment with HVEF had a range of indirect effects on anti-oxidative enzymes in wheat plants, and on the population dynamics of S. avenae, thus it may provide a new tool for aphid control. Additional research is needed to assess its effects on wheat aphids under field conditions. After further risk assessments, we may find a new approach for ecological control of aphids with HVEF. 参考文献 相似文献 引证文献

ВПЛИВ ХРОМОСОМИ ELYMUS SIBIRICUS НА АГРОНОМІЧНІ ОЗНАКИ У ДИСОМНО-ДОПОВНЕНОЇ ЛІНІЇ ОЗИМОЇ М’ЯКОЇ ПШЕНИЦІ

There were evaluated the differences between the line and grade «Obriy» created on its base disomno-supplemented line «O27-2», which was bearing the alien signs of resistance to leaf rust and the leaf trichomes on amfiploida Elymus fertile. It is mainly determined by the negative impact of alien chromosomes on the characteristics of the main spike (length, amount of spikelets and grains, grain weight), plant height, number and weight grains with the regrowth. But signs: productive tillering, the length of the main spike, amount of spikelets in the main spike, grain mass from the main spike, with the regrowth and, in general, with the plants – some is influence substantially modified by the conditions of the year. Supplemented line the higher was characterized by thousand kernel weight, in accordance with a recurrent form. Specified chromosome significantly increases plant resistance to leaf rust, but has no effect on the response of plants to be affected with powdery mildew, yellow and stem rust, septoria blight, barley yellow dwarf virus in which both lines showed susceptibility.

The effects of Gibberella zeae, Barley Yellow Dwarf Virus, and co-infection on Rhopalosiphum padi olfactory preference and performance

Insect-borne viruses promote several changes in plant phenotype, which can modify plant-vector interactions in favor of virus survival and dissemination. Although co-infections commonly occur in the field, little is known about their effects on interactions with the vector. The ecological interactions between Barley Yellow Dwarf Virus (BYDV) and its aphid vector, Rhopalosiphum padi, have been investigated extensively, but the vector’s behavior in more complex scenarios has yet to be examined. We assessed olfactory response and performance of R. padi to wheat singly and doubly infected by the pathogenic fungus Giberella zeae and BYDV. Non-viruliferous aphids preferred odors of BYDV-infected wheat over healthy wheat, as previously reported in the literature, and they were still preferentially attracted to BYDV-infected plant during co-infection. However, around 35% more non-viruliferous aphids chose healthy wheat over G. zeae-infected wheat. Viruliferous aphids did not show any preference to the treatments. BYDV-infected wheat was a superior host than healthy wheat for the aphids whose population increased in 25%. We observed a synergistic effect of the co-infected wheat, which was the best host for aphids, and promoted an elevation of 42% on population growth. Our results indicate that co-infection might be beneficial for virus spread as does not interfere with aphid olfactory preference and provides greater colony growth than in singly infected plants.

Evidence for additive effects of virus infection and water availability on phytohormone induction in a staple crop

Infection with phytoviruses influences plant responses to environmental stress, but the biochemical mechanisms underlying these interactions are unknown. Infection of wheat (Triticum aestivum) with a cereal virus (Barley yellow dwarf virus, BYDV) has context-dependent effects on plant productivity and survival conditional to water stress, and we hypothesized this was due to phythormone induction resulting from virus infection. We tested whether BYDV infection and water availability interact to influence hormone profiles in wheat across multiple time periods. Wheat plants were inoculated with BYDV by exposing them to infectious aphids (Rhopalosiphum padi). Concentrations of five hormones (abscisic acid, jasmonic acid, methyl jasmonate, methyl salicylate [MS], and salicylic acid [SA]) in leaf tissues were compared to concentrations in plants exposed to noninfectious aphids (sham treatment) and nondamaged control plants for five time-since-infection periods (0, 8, 16, 24, and 32 d) and two levels of water availability (0.2 and 0.8 g H20/g soil). Three important findings emerged: (1) total hormone concentrations in BYDV-infected plants exceeded concentrations in sham-treated and control plants up to 16 d following infection, after which nondamaged plants exhibited the highest concentrations of hormones; compared with nondamaged and BYDV-infected plants, hormone levels were reduced in sham-treated plants; (2) inoculation treatment affected concentrations of MS and SA: SA concentrations were increased in BYDV-infected plants, but control plants exhibited higher MS concentrations than either BYDV-infected or sham-treated plants irrespective of watering treatments and across all time periods; and (3) correlation analysis revealed no evidence of hormonal cross-inhibition. This study provides the first evidence that BYDV infection elevates both total phytohormone levels and SA in wheat in a time-sensitive manner, suggesting a potential biochemical basis for virus-induced hormonal responses that alter plant responses to environmental stress.

Development of monoclonal antibodies and serological assays specific for Barley yellow dwarf virus GAV strain

BackgroundBarley yellow dwarf virus (BYDV) is one of the most devastating plant viruses and belongs to a ubiquitous plant virus group. In China, four BYDV strains (GPV, GAV, PAV and RMV) have been identified based on their specific aphid vectors and serological properties. Among the four identified strains, the GAV is the most common BYDV strain in China. To diagnose, forecast of BYDV GAV, two reliable serological assays for BYDV GAV detection were established.MethodsWe purified virion from a confirmed BYDV GAV source and used it as the immunogen to produce monoclonal antibodies against the virus. Using the hybridoma technology, three highly specific murine monoclonal antibodies were produced and two serological assays [antigen-coated-plate enzyme-linked immunosorbent assay (ACP-ELISA) and dot enzyme-linked immunosorbent assay (dot-ELISA)] were established for the BYDV GAV detection.ResultsAll three monoclonal antibodies reacted strongly and specifically with the BYDV GAV strain in crude leaf extracts. Titers of the monoclonal antibodies in ascitic fluids were up to 10−7 by indirect-ELISA. These three monoclonal antibodies (18A1, 18A9 and 12A11) all belonged to the isotype IgG1, kappa light chain. The highest dilution points for the three antibodies during the ACP-ELISA using infected crude leaf extracts were 1:163,840, 1:81,920 and 1:81,920 (w/v, g · mL−1), respectively. Result of dot-ELISA showed a successful detection of BYDV GAV strain in 1:5,120 (w/v, g · mL−1) diluted wheat leaf crude extracts. Analysis of 22 field wheat leaf samples and 33 aphid samples from the Shaanxi Province in China, using the two newly developed assays confirmed the presence of BYDV GAV in about 80 % of the wheat samples and 18 % of the aphid samples.ConclusionsAll three monoclonal antibodies are highly sensitive and specific to the BYDV GAV. The two newly developed serological assays are simple and effective. These two assays, particularly the dot-ELISA, are useful for high throughput detection of BYDV GAV in host plants and aphid vectors.

Do Secondary Bacterial Endosymbionts of Aphids Affect the Vector Specificity or Transmission Efficiency of Plant Viruses?

Several vectoring insects, such as aphids and white fly, harbour secondary bacterial endosymbionts. When an insect vectors a persistently transmitted plant virus, this virus should pass through the insect gut into the haemolymph. The secondary bacteria, however, may affect the movement, persistence and replication of the viruses, thereby influencing the vectoring efficacy or specificity of the insect in respect to these plant viruses. This issue, however, has not yet been fully investigated. Hence, the aim of this primary study is to investigate the effect of secondary bacterial endosymbionts of Sitobion avenae clones in respect of the vector specificity and transmission efficiency of barley yellow dwarf virus, as well as to highlight in general the role of secondary bacteria in virus transmission. The experiments were performed according to standard protocols using one virus strain, BYDV-PAV, and four S. avenae clones harbouring different bacterial and genetic profiles. We found that all tested clones we...

Environmentally dependent host–pathogen and vector–pathogen interactions in the Barley yellow dwarf virus pathosystem

Summary Understanding environmentally dependent variation in interspecific interactions is needed for evaluating how agroecosystems respond to abiotic stressors, including climate change. Both biotic and abiotic conditions shape crop responses to stress events, but interactions between environmental conditions and insect borne plant pathogens remain poorly understood. We tested the hypothesis that drought stress, as applied by experimental water deprivation, drives conditional outcomes in host–pathogen and host–vector interactions using a cereal–aphid–virus association and greenhouse experiments. Under conditions of ample water supply, infection of wheat plants with Barley yellow dwarf virus (BYDV) resulted in reduced above‐ground growth, seed set, seed yields and seed germination compared with plants exposed only to non‐infected (non‐viruliferous) aphids or control plants not subjected to aphid infestation. However, when water was chronically limiting, infection with Barley yellow dwarf virus did not significantly affect plant performance. When wheat was subjected to acute drought stress, plants infected with Barley yellow dwarf virus surpassed both control plants and plants exposed to non‐infected aphids in all measured performance traits. Feeding experiments with aphid vectors (Rhopalosiphum padi) and subsequent life table analysis revealed that aphid fecundity improved by 47% when feeding on Barley yellow dwarf virus‐infected plants when water inputs were chronically low. However, when plants received ample water, aphid fecundity was enhanced by only 23% from feeding on BYDV‐infected plants. Synthesis and applications. Collectively, our experiments suggest that wheat– Barley yellow dwarf virus interactions shift along gradients of water stress severity and duration. When Barley yellow dwarf virus infection preceded water deprivation, plant performance was not reduced from virus infection, and infected plants recovered from severe stress events more readily than non‐infected plants. However, vector–pathogen mutualism resulting in enhanced reproduction of aphids on virus‐infected plants is likely to amplify direct plant injury from herbivory in the field. Our findings indicate that during periods of drought, management of Barley yellow dwarf virus infection may not be needed and infection could benefit wheat under conditions of acute water stress.