Symptom expression of yellow leaf disease in sugarcane cultivars with different degrees of infection by Sugarcane yellow leaf virus

Sugarcane yellow leaf virus (ScYLV) is present in many sugarcane growing areas of the world. It is suspected to cause yellow leaf disease (formerly called YLS, yellow leaf syndrome) of sugarcane. This study investigated symptom expression in a selection of cultivars classified into three groups; ScYLV-susceptible/infected, ScYLV-resistant and intermediately infected cultivars grown in plantation fields in the islands of Hawaii. Incidence of yellow leaf symptoms was correlated, though not tightly, to the presence of ScYLV. The correlation is based on two factors: (i) only ScYLV-infected cultivars (from both susceptible and intermediate groups) showed severe symptom expression, and (ii) ScYLV-infected plants had four times higher symptom incidence than virus-free plants of the same cultivar. The yellow leaf symptom expression fluctuated, peaking at 200, 350, 500 and 600 days after planting. These symptom peaks were correlated with an increase of ScYLV content in the intermediately infected group of cultivars. No nutritional, environmental or field factor could be identified which clearly influenced symptom expression. It is speculated that the symptom expression is elicited by assimilate backup in the stalks and that the fluctuation of symptom expression is caused by the growth rhythm of mature sugarcane stalks.     

Elimination of Sugarcane yellow leaf virus from infected sugarcane plants by meristem tip culture visualized by tissue blot immunoassay

Sugarcane yellow leaf virus (SCYLV), a member of the Luteoviridae , is implicated in the sugarcane disease known as yellow leaf syndrome (YLS), which is characterized by yellowing of the leaf midrib followed by leaf necrosis and possible growth suppression. YLS is distributed worldwide and susceptible cultivars are commonly infected with SCYLV. However, not all cultivars infected with SCYLV show symptoms of YLS and some cultivars that show symptoms do so sporadically. Since it is difficult to obtain virus-free plants of susceptible cultivars, it has not been possible to study the factors involved in SCYLV infection nor the effects of infection on plant growth and yield. A tissue blot immunoassay was used to visualize in vivo presence of the virus so that virus-infected and virus-free plants could be distinguished. Meristem tip cultures were used to produce virus-free plantings of six SCYLV-susceptible sugarcane cultivars. Nearly all of the regenerated sugarcane lines remained virus-free over a period of up to 4 years, whether grown in isolated fields or in the glasshouse. Experimental re-infection of the virus-free plants by viruliferous aphids demonstrated that meristem tip culture did not affect susceptibility of sugarcane to SCYLV. Improved diagnosis and production of virus-free plants of SCYLV-susceptible cultivars will facilitate research to quantify the effect of the virus on yield and to analyse the processes involved in disease development.     

Transmission, characterization, and serology of a luteovirus associated with yellow leaf syndrome of sugarcane

ABSTRACT A previously uncharacterized luteovirus was associated with one form of yellow leaf syndrome (YLS), a widespread disease of sugarcane (Saccharum sp.). The virus was named Sugarcane yellow leaf luteovirus (ScYLV), and was identified in major sugarcane-producing areas of the world. Typical disease symptoms were reproduced when ScYLV was transmitted by Melanaphis sacchari or Rhopalosiphum maidis from infected to healthy sugarcane, suggesting that this virus may be the causal agent of one form of YLS. The only known hosts of ScYLV are Saccharum and Erianthus spp. Virions of ScYLV were 24 to 29 nm in diameter in sodium phosphotungstate at pH 5.0, had a buoyant density of 1.30 g/cm(3) in Cs(2)SO(4), and contained a 5.8-kb genomic ssRNA. The capsid protein had an estimated relative molecular mass of 27 kDa and was not glycosylated. A polyclonal rabbit antiserum raised against ScYLV did not detect any of eight other luteoviruses by enzyme-linked immunosorbent assay or immunosorbent electron microscopy, but in immunoblot assays, antibodies to ScYLV detected the RPV serotype of Barley yellow dwarf luteovirus. It is concluded that ScYLV is a previously undescribed luteovirus that is biologically and serologically distinct from other members of the group and may be the causal agent of one form of YLS of sugarcane.     

Strawberry virus diseases1

To prevent damage to strawberry from virus diseases one must plant only virus-free stock and grow it under insect-proof conditions. Indexing for virus infection to monitor the introduction and spread of viruses should be carried out at every stage of development of nursery stock. Most strawberry viruses are aphid-transmitted, and some nematode-transmitted. Mottle, crinkle and mild yellow edge are the most economically important diseases, especially in combination. Virus infection causes loss of plant vigour, growth, reduced yield, fruit quality, off-colour of leaves, and reduced leaf size. Virus spread is more rapid during spring and autumn, varying greatly by year and place according to aphid populations and weather.     

Spread of <Emphasis Type="Italic">Sugarcane yellow leaf virus</Emphasis> in initially disease-free sugarcane is linked to rainfall and host resistance in the humid tropical environment of Guadeloupe

Sugarcane yellow leaf virus, the causal agent of yellow leaf, is transmitted from plant to plant by aphids. Understanding and evaluating the epidemic risks due to spread of yellow leaf by aphids is an important feature for sugarcane production. Four distinct sugarcane trials were set up with disease-free plants to study the relationship between spread of yellow leaf, the vector dynamics and environmental conditions that may favour yellow leaf epidemics. The study was performed by surveys of vector populations and determination of plant infections. Sugarcane cultivar SP71-6163, highly susceptible to yellow leaf, was analyzed spatially at different dates in all four trials and compared to commercial cultivars in two of the four trials. These surveys allowed us to identify a correlation between the aphid dynamics in the field and yellow leaf progress. Additionally, a negative correlation was found between rainfall during the first weeks after transferring sugarcane plants to the field and aphid dispersal within the field. This later result revealed an impact of rainfall on aphid invasion and subsequent plant infection by SCYLV. If aphids are the key factor for disease spread, plant response varied also according to cultivar resistance with high variation depending on rain conditions.     

The Use of Molecular Beacons Combined with NASBA for the Sensitive Detection of Sugarcane Yellow Leaf Virus

Sugarcane yellow leaf virus (ScYLV) is widely distributed in Brazil and other sugarcane producing countries causing significant yield losses. Due to the high incidence of the aphid vector, the virus is widespread in the field and in parental clones used in sugarcane breeding programmes. Aiming to present a sensitive and reliable detection of ScYLV, we have adapted an AmpliDet RNA system, compared it with the currently available detection methods and discussed its applicability for routine diagnosis. AmpliDet RNA consists of nucleic acid sequence-based amplification (NASBA) of the target RNA with specific primers and simultaneous real-time detection of the amplification products with molecular beacons. The results showed that the system produced a detection level of at least 100fg of purified virus. Virus was readily detected in plant tissues with low levels of infection (without the need of previous RNA extraction) and in the hemolymph of aphids. The method showed to be virus-specific, testing negative for other species of the Luteoviridae. In conclusion, the system has potential to become a diagnostic method for the detection of sugarcane viruses.     

人工饲料条件下大麦黄矮病毒GAV株系对麦长管蚜种群适合度的直接影响

植物病毒与介体蚜虫存在复杂的互作关系。前人关于植物病毒对蚜虫调控作用的研究主要集中在植物病毒通过寄主植物对蚜虫的间接影响上,未见植物病毒对介体蚜虫适合度直接调控的报道。鉴于此,我们以麦长管蚜Sitobion miscanthi (Takahashi)为试虫,以其传播的大麦黄矮病毒-GAV(Barley yellow dwarf virus GAV,BYDV-GAV)为测试病毒,以全纯人工饲料加入BYDV-GAV病毒提取液饲养麦长管蚜4 d,使之在不接触寄主植物条件下获毒,然后分别在全纯人工饲料和无毒小麦叶片上继续饲养,直至死亡。利用生命表技术分析麦长管蚜生长发育和繁殖参数。研究结果表明:在无毒小麦叶片饲养条件下,与未获毒对照麦长管蚜相比,获毒后麦长管蚜生活史参数成虫历期和产仔天数显著降低,繁殖力显著增加;种群参数内禀增长率、净繁殖率、周限增长率显著增加,平均世代周期显著降低。在全纯人工饲料条件下,与未获毒对照相比,获毒后麦长管蚜仅成虫历期和产仔天数显著下降,而其他生活史参数及种群参数均无显著差异。说明BYDV-GAV使得介体麦长管蚜在小麦叶片上的适合度显著提高,这是由麦长管蚜与寄主植物互作引起的,而病毒对介体麦长管蚜的适合度无直接调控作用。     

6种病毒抑制剂对西藏青稞上大麦黄矮病的防治效果

通过田间小区试验,开展了6种病毒抑制剂对西藏青稞上大麦黄矮病防治效果的研究.采用带毒蚜虫人工接种法,于青稞起身拔节期每株接种10～15头带毒麦长管蚜,7 d后灭蚜,灭蚜后3d喷施病毒抑制剂,在成株期出现黄矮病症状后调查病株率、病情指数、防治效果,以及长势和产量.结果表明,6种病毒抑制剂对青稞上大麦黄矮病有不同程度的防治...     

Interference between potyviruses during aphid transmission

Single aphids ( Myzus persicae ) were allowed sequential access to two leaves which were either free from infection or infected with potato virus Y° (PVY°). PVY^N. beet mosaic virus (BMV), or tobacco mosaic virus (TMV). Aphids given prior or subsequent access to PVY^N-infected leaves transmitted PVY° and BMV less frequently than aphids given prior or subsequent access to virus-free leaves; those given prior or subsequent access to BMV also transmitted PVY° less frequently. However, prior or subsequent access to PVY° did not decrease transmission of either BMV or PVY^N, and access to BMV did not decrease transmission of PVY^N. Access to the non-aphid-transmissible TMV did not affect transmission of either PVY° or PVY^N. PVY^N had the greatest electrophoretic mobility. BMV was least mobile and PVY° was intermediate, so ability to decrease transmission was not directly related to the total anionic charge on the virus particles.     

Symptoms, aetiology and serological analysis of sweet potato virus disease in Uganda

Sweet potato virus disease (SPVD) is the name used to describe a range of severe symptoms in different cultivars of sweet potato, comprising overall plant stunting combined with leaf narrowing and distortion, and chlorosis, mosaic or vein-clearing. Affected plants of various cultivars were collected from several regions of Uganda. All samples contained the aphid-borne sweet potato feathery mottle potyvirus (SPFMV) and almost all contained the whitefly-borne sweet potato chlorotic stunt closterovirus (SPCSV). SPCSV was detected by a mix of monoclonal antibodies (MAb) previously shown to react only to a Kenyan isolate of SPCSV, but not by a mixture of MAb that detected SPCSV isolates from Nigeria and other countries. Sweet potato chlorotic fleck virus (SPCFV) and sweet potato mild mottle ipomovirus (SPMMV) were seldom detected in SPVD-affected plants, while sweet potato latent virus (SPLV) was never detected. Isolates of SPFMV and SPCSV obtained by insect transmissions together induced typical symptoms of SPVD when graft-inoculated to virus-free sweet potato. SPCSV alone caused stunting and either purpling or yellowing of middle and lower leaves when graft-inoculated to virus-free plants of two cultivars. Similarly diseased naturally inoculated field plants were shown consistently to contain SPCSV. Both this disease and SPVD spread rapidly in a sweet potato crop.     

广东甘蔗黄叶病田间调查及病原病毒的分子检测

 广东省粤北和粤西蔗区多个县市的田间甘蔗上观察到甘蔗黄叶病(Sugarcane yellow leaf disease,SYLD)典型症状,目前该病仅局部分布,但部分田块病株率为5%~80%,发病品种有青皮果蔗、黑皮果蔗、新台糖系列品种、粤糖79/177和粤糖93/159等。采集发病田间显症叶片、无症叶片和在病叶上取食的甘蔗绵蚜(Ceratovacuna lanigera)样品,抽提总RNA,以基于甘蔗黄叶病毒(Sugarcane yellow leaf virus,SCYLV) CP基因序列的特异引物进行一步RT-PCR和巢式PCR扩增,并对扩增产物进行核苷酸序列测定和BLAST比对。结果显示,RT-PCR及巢式PCR产物核苷酸序列与分离自巴西的SCYLV B1株系相应区段同一率为100%;一步RT-PCR可从约70%的显症叶片样品中检测到SCYLV,而病田中的无症叶片样品以及在病叶上取食的单头甘蔗绵蚜样品需经巢式PCR扩增方可检测到SCYLV,阳性率分别为1%~5%和83%。本研究表明,广东省栽培甘蔗已受到SCYLV侵染,甘蔗绵蚜携带SCYLV。     

Wind-mediated spread of Rice yellow mottle virus (RYMV) in irrigated rice crops

A study was carried out to demonstrate that Rice yellow mottle virus (RYMV), a virus known to be transmitted by beetles, can spread between rice plants by direct leaf contact caused by wind. Almost all healthy plants surrounding an infected plant became infected when exposed to a fan blowing for 15 min at a distance of 50 cm. Spread of RYMV by plant contact, mediated by wind, was also demonstrated in field experiments, the extent of spread depending on plant density. Infection was almost 10 times higher in plots with a density of 33 plants m⁻² than in plots with 16 plants m⁻². Less spread was observed in plots protected by 1·5 m high windscreens. It is suggested that wind-mediated spread of RYMV may result from abrasive contact between leaves of plants.     

Effects of virus infection of faba bean on subsequent infection by Uromyces viciae-fabae

Prior infection of faba bean with bean yellow mosaic virus (BYMV) and bean leaf roll virus decreased pustule density on leaves subsequently infected by Uromyces viciae-fabae. Changes were most marked on young leaves showing conspicuous symptoms of systemic virus infection and in plants virus-infected for at least 2-4 weeks. Pustule density progressively decreased when inoculations were made with uredospore generations successively produced on and inoculated to BYMV-infected leaves.
Uredospore germination and germ tube length were similar on virus-free and BYMV-infected leaves and on agar seeded with spores produced for one or several generations on BYMV-infected or virus-free plants. Formation of appressoria was slightly reduced on BYMV-infected leaves but changes in the post-penetration development of the rust probably accounted for much of the decreased pustule production encountered.     

甘蔗黄叶病毒运动蛋白的原核表达和抗血清制备

甘蔗黄叶病毒(Sugarcane yellow leaf virus,ScYLV)属于黄症病毒科(Luteoviridae)、马铃薯卷叶病毒属(Polerovirus),主要由蚜虫传播,能够侵染甘蔗、玉米等多种作物,引发严重的植物病害。本研究将编码ScYLV运动蛋白(Movement protein,MP)的基因连接到pDB-His-MBP原核表达载体上,转化到大肠杆菌菌株Rosetta中,经IPTG诱导,表达分子量大小约为70 kDa的融合蛋白,将纯化后的融合蛋白制备多克隆抗血清。利用western blot检测抗血清的效价为1∶128 000,灵敏度为1∶256,抗血清不与马铃薯卷叶病毒属(Polerovirus)的其它病毒以及黄症病毒属(Luteovirus)病毒发生交叉反应,具有很好的特异性。本文制备的ScYLV MP抗血清可以用于ScYLV的检测,并为深入研究ScYLV与寄主的相互作用等问题提供材料基础。     

一种蚜虫持久性传病的长豇豆黄化型病毒

 1983年6月,在南京郊区的长豇豆上采到1株表现植株矮缩症状的C-7病毒分离物。接种试验证明,它不能摩擦接种传病,但可以由豆蚜(Aphis craccivora)、棉蚜(A.gossypii)和桃蚜(Myzus persicae)以持久性方式传病。寄主范围测定的结果表明:分离物可以侵染长豇豆、豇豆、蚕豆、大豆、菜豆、豌豆、赤豆、利马豆、苜蓿、红三叶、地三叶、绛三叶、葫芦巴,紫云英和苕子等15种豆科植物和曼陀罗1种茄科植物。这些植物大都出现植株矮化,叶片扭曲,卷缩或僵缩,不能开花结实等症状。豆蚜的传病性状中,获毒饲育的最短传病时间为3小时,接毒饲育最短传病时间为10分钟,循回期是24小时左右。但是,传病率最高的获毒饲育时间是2~3天,接毒饲育时间在1天以上。接种1头蚜虫就具有传病能力,5头蚜虫能达到100%的传病率。蚜虫可以终身传毒,蜕皮不影响其传毒力,但传毒有间歇性。根据它的基本性状,病毒C-7分离物是一种豆科植物的黄化型病毒,可能是属于大麦黄矮病毒组(Luteovirus Group)的成员。     

灰飞虱传播的一种小麦病毒病鉴定

 在实验室中利用灰飞虱接种小麦时出现一种新的病毒病症状,鉴定表明其病原为大麦黄条点花叶病毒(Barley yellow striate mosaic virus, BYSMV)。采用生物学测定、电镜观察、RT-PCR检测和序列分析的方法,明确了该病毒的粒体特性、危害症状及田间发生情况。接种试验表明该病毒通过灰飞虱传播,接种7~10 d后小麦新生叶片出现黄色斑点、斑驳,继而发展成黄色条纹,叶片对生且细而窄,重病株新叶扭曲,叶鞘不能伸长,病株矮化。对小麦病叶超薄切片电镜观察,发现细胞质中存在大量弹状病毒粒子,病毒粒体大小为（315~353）nm×（46~57） nm。利用特异性引物从病株总RNA中扩增出 565 bp基因片段,序列同源性分析显示与大麦黄条点花叶病毒(Barley yellow striate mosaic virus, BYSMV) Zanjan-1分离物聚合酶（L）基因对应序列的一致性为97 %,与北方禾谷花叶病毒(Northern cereal mosaic virus, NCMV) L基因对应序列的一致性为78 %~79 %。对采自河北邯郸、石家庄、保定、唐山的31株样品进行RT-PCR检测,25株检测到BYSMV,7株检测到水稻黑条矮缩病毒(Rice black streaked dwarf virus,RBSDV),其中5株为2种病毒复合侵染,结果表明BYSMV的田间分布较广。系统发育分析表明BYSMV-Lab/TS/ZX/QY 4个分离物与本研究的BYSMV亲缘关系密切。BYSMV是我国小麦上新发现的一种弹状病毒,并已形成危害,暂定名为小麦黄条纹矮缩病,应加强流行动态监测。     

The Basis for Thinopyrum-Derived Resistance to Cereal yellow dwarf virus

ABSTRACT Incorporation of Thinopyrum intermedium-derived resistance genes into improved wheat germ plasm generated a wheat substitution line (P29) which is completely resistant to Cereal yellow dwarf virus (CYDV). The undetectable CYDV titer in P29 led many to conclude that resistance prevented viral replication. To determine whether CYDV replication or movement is inhibited, we examined inoculated leaves for replication and uninoculated leaves for systemic spread. CYDV subgenomic RNA, produced only during replication, was found within the inoculated area of P29 and T. intermedium leaves, demonstrating that viral replication occurred. Absence of CYDV from uninoculated, newly emerging leaves of inoculated P29 and T. intermedium plants indicated resistance via inhibition of viral systemic infection. Resistance was not effective if P29 was inoculated with 50 to 100 viruliferous aphids per plant at the first-leaf stage or younger, resulting in a systemic spread of CYDV. As these infected P29 seedlings continued to grow, the resistance phenotype was recovered. Our data suggested that T. intermedium-derived resistance to CYDV was primarily dosage dependent and could be developmentally regulated if the amount of inoculum was large enough.     

Biomolecular relationships among isolates of<Emphasis Type="Italic">Tomato Yellow Leaf Curl Tanzania Virus</Emphasis>

An investigation of the biological properties of the virus causing tomato yellow leaf curl disease in Tanzania was initiated to compare it with other known tomato yellow leaf curl viruses. Properties relating to acquisition and inoculation feeding time, persistence, mechanical inoculation, seed transmission and host range were studied. Results obtained indicate that the virus was transmitted persistently byBemisia tabaci Genn., but it was not mechanically, sap- or seed-transmissible. Minimum acquisition and inoculation feeding time was 30 min.Capsicum annuum, Datura stramonium, Nicotiana glutinosa, N. tabacum andLycopersicon esculentum were found to be hosts of the virus among the plant species tested, whereasPhaseolus vulgaris was not. It is concluded that the properties of the agent causing yellow leaf curl symptoms in tomato plants from different regions in Tanzania are similar to those ofTomato yellow leaf curl Sardinia virus species studied elsewhere. http://www.phytoparasitica.org posting Feb. 20, 2003.     

地黄脱毒技术及增产效果

对地黄脱毒技术进行了研究.从6种不同浓度激素组合的培养基中,筛选出地黄茎尖培养较适宜的培养基为MS 6-BA 1mg/L NAA 0.1mg/L,不同地黄品种在该培养基上的茎尖培养成苗率为76.6%～90.5%;适宜的快繁培养基为MS 6-BA 0.3mg/L NAA 0.02mg/L GA 0.1mg/L.建立了地黄茎尖苗的病毒检测技术,培育出4个地黄品种的脱毒苗,茎尖苗的平均脱毒率为52.3%.对地黄脱毒苗与非脱毒苗的生育性状、田间发病率及产量进行了比较,脱毒地黄种苗的株高、叶面积和叶片数明显高于非脱毒苗;脱毒地黄地上部病毒病的显症率明显下降,新生叶片数增加;脱毒地黄的增产幅度为16.5%～45.5%,平均31.0%.     

毒株、苗龄及温度对烟草苗期接种TMV试验的影响

病毒株系、苗龄、接种后培养条件是影响烟草病毒病发生发展的关键因素,为确保烟草接种TMV抗性鉴定和药效生测试验的准确性,在NV基因烟草和普通烟草上接种TMV,采用病毒生物学、qRT-PCR和Western blot技术,研究病毒的分离纯化、株系、稀释限点、传导路径、病害症状,以及N基因抗TMV的温敏性.结果显示,TMV为...