Uneven distribution of two potyviruses (feathery mottle virus and sweet potato latent virus) in sweet potato plants and its implication on virus indexing of meristem derived plants

Abstract

The distribution of two sweet potato potyviruses, FMV and SPLV, was assessed in three plants infected with both viruses and in one plant infected with FMV only. All leaves, the top and basal sections of the main stem, and branch sections were tested by ELISA. Both symptomless leaves and leaves showing symptoms including purple rings, chlorotic spots, mottle or discoloration were found to contain the viruses. However, neither could be detected in every leaf or stem piece. SPLV was found in a lower proportion of leaf and stem samples than FMV. This indicates that the two viruses are either very unevenly distributed within sweet potato plants or that the virus concentration in some parts is below the detectable level. Testing of each leaf is recommended for reliable virus indexing of small, meristem‐derived sweet potato plantlets, if the ELISA method is used. Additional indexing of all ELISA‐negative materials by grafting to susceptible indicator plants is nevertheless still necessary.     

An investigation of the reliability of ELISA as a practical test for detecting potato leaf roll virus and potato virus Y in tubers

Enzyme-linked immunosorbent assay (ELISA), involving mechanical sampling of tubers, was compared with a growing-on test in which virus was assessed visually, and with ELISA on leaves. The percentage infection of potato leaf roll virus and potato virus Y on samples of potential seed tubers sent for advisory test during the winter, was determined by each method. The tuber ELISA underestimated the incidence of both viruses, and was less accurate than the growing-on or leaf ELISA. The effect on the reliability of tuber ELISA of the amount and distribution of virus in the tuber, the compromises made to make the test fast and simple, and the quality of anti-serum and composition of the extraction buffer are discussed.     

甘肃省大丽花病毒病病原鉴定及病生理研究

经对受病毒感染的甘肃省临洮县大丽花进行间接ELISA和鉴别寄主测定,结果表明黄瓜花叶病毒(CMV)是其病原之一。田间调查表明大丽花病毒病在甘肃临洮县发生普遍,发病率达36%;其主要症状有花叶、卷叶花叶、蕨叶和矮缩。不同大丽花品种之间病毒病发病率有一定的差异,在调查的8个品种中‘鹦嘴红’发病率最低,只有7.43%,而‘洮阳荷花’发病率最高,达到42.47%。大丽花感染病毒后叶绿素(a+b)比正常的下降了23.61%;在叶片组织病变观察中,发现叶片感染病毒后叶绿体内的淀粉颗粒含量增多且肿大,油粒增多,几乎占满整个叶绿体结构。     

Detection of Citrus psorosis virus in field trees by direct tissue blot immunoassay in comparison with ELISA, symptomatology, biological indexing and cross-protection tests

Serological detection of Citrus psorosis virus (CPsV) by direct tissue blot immunoassay (DTBIA) and by double (DAS) and triple (TAS) antibody sandwich ELISA, was compared in samples from various citrus varieties growing in the glasshouse and in the field. In young shoots and leaves, CPsV was readily detected by the three procedures, whereas DTBIA detection in old leaves was less consistent. DTBIA detection and ELISA readings in nine different citrus varieties were similar, suggesting that CPsV accumulates to equivalent levels in all of them. In infected field trees from Spain or Italy, CPsV was consistently detected by TAS ELISA, even in samples of old leaves in winter, whereas DTBIA detection in the same trees was reliable only when using young shoots. Detection of CPsV by DTBIA and by DAS and TAS ELISA in previously untested field trees correlated perfectly with psorosis diagnostics based on biological indexing, specifically with the capacity of those sources to cross-protect against challenge inoculation with psorosis B. Some trees without bark scaling were shown to be psorosis-infected by biological indexing and to contain CPsV by serological tests; other trees showing psorosis-like bark or leaf symptoms in the field were shown to be psorosis-free by biological indexing and also CPsV-free by serology. This is the first time that the presence of CPsV has been correlated with psorosis infection as diagnosed by biological indexing.     

应用单克隆抗体检测香蕉束顶病

应用香蕉束顶病毒（ＢＢＴＶ）的单克隆抗体（ＭｃＡｂ）建立了检测香蕉束顶病的间接ＥＬＩＳＡ方法，其检测香蕉病组织汁液的最大稀释度为１：１２８０，健康香蕉组织汁液无非特异性反应。用间接ＥＬＩＳＡ方法检测了采自广东、广西９个市（县）的香蕉产区的８０个大田香蕉束顶病样本和２５个荫棚香蕉试管苗样本，其中大田样本ＢＢＴＶ的带毒率为７６．５％，试管苗样本的带毒率为８．０％。香蕉束顶病株不同部位ＢＢＴＶ含量检测表     

从葎草中检出复合侵染的多种病毒

采用抗原直接包被酶联免疫吸附测定法（ELISA）对采自重庆近郊的34个葎草样品进行了主要病毒种类的检测。其中马铃薯Y病毒(Potato virus Y, PVY)的侵染最普遍,其阳性检出率达44.12%;马铃薯X病毒(Potato virus X, PVX)的阳性检出率最低,仅为26.47%,其余5种病毒,烟草花叶病毒(Tobacco mosaic virus, TMV)、黄瓜花叶病毒(Cucumber mosaic virus, CMV)、番茄花叶病毒(Tomato mosaic virus, ToMV)、芜菁花叶病毒(Turnip mosaic virus, TuMV)及蚕豆萎蔫病毒2号(Broad bean wilt virus 2, BBWV-2)的阳性检出率均为35.29%。葎草样品受多种病毒的复合侵染现象非常严重,15个阳性样品中病毒复合侵染率为80%,其中75%的样品检测到7种病毒复合侵染。     

Viruses and virus diseases of grapevine in Tunisia

Mature canes were collected from vines in the main grapevine-growing areas in Tunisia (Cape Bon, Bizerte, Ben Arous), from commercial vineyards and mother-plant plots, to assess the presence of virus and virus-like diseases. Biological (mechanical transmission onto herbaceous hosts and grafting onto indicator woody plants) and serological detection (ELISA) methods were applied. ELISA showed that 96.4% of 669 vines tested were infected, most of them (88.1%) by at least two viruses. Grapevine leafroll-associated 3 closterovirus (GLRaV-3) was the most widespread virus (87.9%), followed by grapevine A vitiviras (GVA, 69.4%), grapevine fleck virus (GFkV, 51.9%), grapevine leafroll-associated 1 closterovirus (GLRaV-1, 36.8%), grapevine leafroll-associated 2 closterovirus (GLRaV-2, 19.1%), grapevine fan leaf nepovirus (GFLV, 18.2%) and grapevine B vitiviras (GVB, 14.8%). ELISA tests yielded negative results for grapevine leafroll-associated 7 closterovirus (GLRaV-7) and potato X potexvirus (PVX). The highest infections were found in Bizerte and Cape Bon regions (100 and 99.2%), and in vineyards aged over 20 years (98.5%) as compared with the younger ones (81.1%). Rootstocks in mother-plant plots were practically free from all the viruses tested (1 plant infected out of 81), whereas severe infections were found in Vitis vinifera mother plants (67.4% of 341 samples), in particular table grapes (92.6%) compared with wine grapes (47.9%). In these mother-plant plots, the prevailing viruses were GLRaV-3 (41.3%), followed by GFkV (36.7%), GVA (27.9%), GLRaV-1 (17%) and GLRaV-2 (15.2%). GFLV and GVB were far more limited (1.5 and 0.6%, respectively). The presence of vein necrosis and vein mosaic was ascertained by transmission onto 110R and Vitis riparia indicators, whereas only GFLV was mechanically transmitted onto herbaceous hosts (from about 20% of the samples).     

Cucurbitaceen-Viren und der Nachweis ihrer Saatgutübertragung – ein methodisches Problem

Virus diseases of cucurbitaceae are frequently observed. More than 30 different viruses can cause symptoms on leaves and fruits. Quality as well as yield can be drastically affected. In some cases the source of infection is unknown. Therefore studies to elucidate a possible virus contamination of seeds and seed transmission of viruses were carried out at the Bavarian State Research Center for Agriculture (LfL). Seed samples of cucurbitaceae were sown in the greenhouse and plants were cultivated. The presence of viruses in fruits was checked by DAS-ELISA. A high percentage of samples were tested positive by ELISA, but these results could not be verified by other methods (tests on indicator plants, RT-PCR). Also electron microscopic investigations at the German Federal Authority and Federal Research Centre (BBA), Braunschweig, gave negative results. Thus a virus contamination of the seed samples was not detected.     

Field evaluation of systemic imidacloprid for the management of avocado thrips and avocado lace bug in California avocado groves

BACKGROUND: The efficacy of systemic applications of imidacloprid for the management of avocado thrips and avocado lace bug was determined in field trials. Following insecticide treatment by chemigation, leaves of appropriate age for each insect were sampled over a 6 month period and used for bioassays. Imidacloprid residues were measured by ELISA in leaves used for bioassays to determine concentrations of insecticide that were toxic to both pests. RESULTS: The uptake of imidacloprid into treated trees was extremely slow, peaking in the current year's leaf flush at only 8 ng cm^?2 leaf tissue after 15 weeks. Avocado thrips mortality in bioassays with young flush leaves, the preferred feeding substrate for this insect, was minimal, indicating that imidacloprid concentrations were below threshold levels needed for effective control. Residues present in older leaves, which are preferred by the avocado lace bug, were higher than in young flush leaves, and provided good control of this pest. Probit analysis of bioassay data showed that the avocado lace bug (LC₅₀ = 6.1 ng imidacloprid cm^?2 leaf tissue) was more susceptible to imidacloprid than the avocado thrips (LC₅₀ = 73 ng imidacloprid cm^?2 leaf tissue). CONCLUSIONS: In spite of the slow uptake of imidacloprid into avocado trees, the levels of imidacloprid would be sufficient to control avocado lace bug infestations. In contrast, the slow uptake would be problematic for avocado thrips control because inadequate levels of insecticide accumulate in new flush foliage and would allow avocado thrips populations to build to levels that would subsequently damage developing avocado fruit. Copyright © 2010 Society of Chemical Industry     

云南、福建、湖南烟区烟草花叶病主要病毒种类检测及黄瓜花叶病毒亚组鉴定

 采用抗原直接包被和双抗体夹心酶联免疫吸附测定法(ELISA)对采自云南、福建、湖南烟区烟草花叶病样品进行了病毒种类检测,利用三抗体夹心ELISA对黄瓜花叶病毒(Cucumber mosaic virus,CMV)的亚组类型进行了鉴定。在云南采集的520个花叶病样品中,烟草花叶病毒(Tobacco mosaic virus,TMV)、CMV和马铃薯Y病毒(Potato virus Y,PVY)总检出率分别为71.74%、55.01%和6.35%;在福建采集的150个花叶病样品中,TMV、CMV和PVY的总检出率分别为94%、24.66%和8.00%;在湖南采集的74个花叶病样品中,TMV、CMV和PVY的总检出率分别为58.11%、51.35%和2.70%。部分样品为2种以上病毒复合侵染。云南、福建和湖南采集的64个CMV阳性样品中,属亚组Ⅰ的样品为57个,占89.1%;属亚组Ⅱ的样品为10个,占15.6%;其中3个样品为亚组Ⅰ和亚组Ⅱ的复合侵染。     

Effect of pokeweed antiviral protein (PAP) on the infection of plant viruses

At a concentration of 0.4 μg purified pokeweed antiviral protein (PAP)/ml, the formation of local lesions on tobacco leaves caused by tobacco mosaic virus infection was completely inhibited and at 25 ng PAP/ ml. 68% inhibition was still obtained. PAP protected plants from infection by viruses from seven virus groups-five RNA viruses: tobacco mosaic virus, cucumber mosaic virus, alfalfa mosaic virus, potato virus X and potato virus Y; and two DNA viruses: African cassava mosaic virus (ssDNA) and cauliflower mosaic virus (dsDNA). Virus infection was probably blocked by PAP at a very early stage. PAP infiltrated into the intercellular spaces through the lower surfaces of leaves inhibited infection by virus inoculated on the upper leaf surface, and partially prevented PVY transmission by aphids. However. PAP did not show any activity against two bacterial and six fungal pathogens.     

西藏昌都市卡若区蔬菜主要病毒检测及番茄斑萎病毒鉴定

为明确西藏昌都市卡若区高原条件下的蔬菜主要病毒种类, 对温室、大棚和露地栽培的主要蔬菜进行了病毒病调查, 采集典型病毒病症状样品进行ELISA检测, 明确病毒种类; 并利用电子显微镜观察, RT-PCR扩增克隆与测序分析对主要病毒进行鉴定分析。ELISA检测结果表明, 西藏昌都市卡若区温室及大棚栽培的番茄、辣椒和莴苣上的主要病毒有番茄斑萎病毒(tomato spotted wilt virus, TSWV)、马铃薯Y病毒(potato virus Y, PVY)及凤果花叶病毒(pepino mosaic virus, PepMV)。其中TSWV检出率最高, 为45%。进一步对检出TSWV的蔬菜样品进行电子显微镜观察, 发现其中含有典型的正番茄斑萎病毒属Orthotospovirus病毒粒体, 应用TSWV-N基因特异性引物进行RT-PCR扩增克隆和序列分析, 发现西藏昌都市卡若区蔬菜感染的TSWV与云南TSWV分离株亲缘关系最近。本研究结果明确了西藏昌都市卡若区蔬菜的主要病毒种类。综合抗体检测、病毒粒体形态观察与分类相关基因的克隆测序结果, 明确了西藏昌都市卡若区蔬菜感染的主要病毒为TSWV。这也是TSWV在西藏的首次报道, 为了解TSWV的发生分布及其防控提供了依据。     

Toxicity of systemic neonicotinoid insecticides to avocado thrips in nursery avocado trees

The efficacies of four systemic neonicotinoid insecticides applied to potted avocado trees at manufacturer-recommended rates were assessed against the avocado thrips, Scirtothrips perseae Nakahara. At the time of treatment, fully expanded first-flush young leaves were tagged for identification, and a proportion of these leaves was used in bioassays with second-instar thrips. At 7 weeks post-treatment, a second flush of leaves had fully expanded on the trees, and these leaves were included in additional bioassays comparing avocado thrips mortality on both first- and second-flush leaves. In bioassays with first-flush leaves, imidacloprid (273 mg AI pot(-1)) was the most effective insecticide, providing at least 70% mortality of thrips for 14 weeks. Thiamethoxam (137 mg AI pot(-1)), clothianidin (109 mg AI pot(-1)) and dinotefuran (241 mg AI pot(-1)) provided good control in bioassays that were conducted within 4 weeks of treatment, but thereafter their efficacies were inconsistent. In bioassays with second-flush leaves, imidacloprid provided at least 70% mortality up to 9 weeks after the insecticide application. Thereafter, mortality declined to 30% or lower. Bioassays with second-flush leaves collected from trees treated with thiamethoxam, clothianidin and dinotefuran resulted in unacceptably low thrips mortality. Monitoring of imidacloprid and thiamethoxam residues by ELISA showed that the greater persistence of imidacloprid in both first and second leaf flushes was due to a steadier uptake of this material. Although thiamethoxam residues rose quickly within the first leaf flush, levels had already begun to dissipate by the time the second leaf flush had started to develop.     

国家种质广州甘薯圃病毒种类鉴定及分析

为明确引起国家种质广州甘薯资源圃中病毒病的病毒种类及优势种,为甘薯种质安全保存提供支持,2017年从甘薯资源圃中未脱毒更新的盆栽苗和大田苗中采集155份具有不同病毒病症状的甘薯资源样品,利用PCR和RT-PCR检测技术对这些样品进行了17种病毒的分子检测.155份样品均有病毒检出,包括甘薯羽状斑驳病毒Sweet pot...     

Survival analysis of time to abscission of blueberry leaves affected by septoria leaf spot

ABSTRACT In the southeastern United States, Septoria leaf spot, caused by Septoria albopunctata, can result in premature defoliation of blueberry plants during summer and fall, thereby reducing yield potential for the following year. The effects of disease severity and leaf attributes (leaf age and leaf location in the canopy) on the dynamics (timing and extent) of defoliation were quantified in field plots of Premier rabbiteye blueberry (Vaccinium ashei) in 2002 and 2003. In each year, 50 shoots were selected for assessment in early spring, and all leaves on these shoots (n = 410 and 542 in 2002 and 2003, respectively) were monitored individually for disease progress and time of abscission at 3- to 10-day intervals throughout the season. In both years, disease progress was characterized by an exponential increase in disease severity up to late September, followed by a decline toward the end of the assessment period in late November. Defoliation was sporadic up to late August, followed by more rapid and sustained levels of leaf loss. Abscission of severely infected leaves could explain the decline in disease severity toward the end of the season. Final disease severity (i.e., disease severity on the last assessment date before leaf drop) was highest for leaves that abscised early and lowest for leaves that had not abscised by the end of the assessment period. Survival analysis revealed that older leaves (located on the lower halves of shoots) and leaves with high levels of disease (>/=5 spots/leaf at the time of fruit harvest in mid-June) abscised significantly (P < 0.0001) earlier than younger leaves and leaves with lower disease severity. Relative to their respective reference groups, mean times to abscission were approximately 2 weeks shorter for the older leaf group and approximately 3 weeks shorter in the leaf group afflicted by high disease severity. When an accelerated failure time model was fitted to the data, the resulting parameter estimates indicated that each additional leaf spot present at harvest accelerated time to leaf abscission (expressed using late August as a starting point) by 1.9 and 4.5% in 2002 and 2003, respectively. Leaf location in upper or lower portions of the canopy had no significant effect on time to abscission (P > 0.05).     

侵染四川辣椒的番茄斑萎病毒和辣椒轻斑驳病毒的小RNA测序检测及鉴定

 调查发现四川省汶川县当地辣椒的病毒病严重且症状多样,病样粗提液摩擦接种辣椒、矮牵牛和三生烟,出现辣椒系统性花叶焦枯和茎尖坏死,指示植物表现局部枯斑。对3个不同症状的病果进行sRNA深度测序鉴定,发现均含有番茄斑萎病毒(Tomato spotted wilt virus,TSWV)和辣椒轻斑驳病毒(Pepper mild mottle virus,PMMoV)。通过RT-PCR技术进行验证,结果显示所有病样的果皮和部分新鲜种子以及回接寄主的病叶均检测到TSWV和PMMoV,表明该地辣椒病毒病是由TSWV和PMMoV复合侵染引起。这是TSWV侵染四川辣椒的首次报道。分别基于TSWV N基因序列和PMMoV CP基因序列构建系统发育树,汶川分离物TSWV-WC(MK468469)与贵州分离物(KP684518)亲缘关系最近,PMMoV-WC(MK408614)与北京分离物(AY859497)亲缘关系最近。推测该地辣椒病毒病可能与品种引进有关。     

Simultaneous detection and identification of eight stone fruit viruses by one-step RT-PCR

A sensitive and reliable one step RT-PCR reaction with an internal control has been developed to detect and differentiate eight important viruses that affect stone fruit tress: Apple mosaic virus (ApMV), Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV), American plum line pattern virus (APLPV), Plum pox virus (PPV), Apple chlorotic leaf spot virus (ACLSV), Apricot latent virus (ApLV) and Plum bark necrosis stem pitting associated virus (PBNSPaV). In addition, we investigated the detection limit and the efficiency of three different nucleic acid extraction methods that avoid the use of organic solvents, for both multiplex RT-PCR and dot-blot hybridisation assays. The primer cocktail was used to analyse 38 stone fruits originating from nine different countries and six species. A large number of virus combinations was detected and up to three different viruses were observed in five samples. A decrease in sensitivity was observed when the primer cocktail contained more than five different pair primers. However, comparative analyses showed that the multiplex RT-PCR containing the eight virus pair primers was even more sensitive than the ELISA or molecular hybridisation assays. The use of the multiplex RT-PCR technology in routine diagnosis of stone fruit tree viruses is discussed.     

北京月季病原病毒的高通量测序鉴定和RT-PCR检测

本研究利用高通量测序技术对北京地区的月季染病样品进行了病毒鉴定,通过序列比对和拼接获得了李属坏死环斑病毒(prunus necrotic ringspot virus,PNRSV)、苹果茎沟病毒(apple stem grooving virus,ASGV)、柑橘碎叶病毒(citrus tatter leaf viru...