甘薯羽状斑驳病毒分离提纯及血清学特性

从感染有甘薯羽状驳病毒的牵牛（I．Nil）叶片,通过超速离心,Cscl密度梯度离心提纯SPFMV粒子,每千克叶片可得病毒13－15毫克。电镜观察病毒粒子长度范围在820－860nm,也可见到900nm以上的特长粒子。病毒提纯物的紫外吸收曲线呈典型核蛋白吸收曲线,OD260／OD280＝1．21,免疫电镜检查,该病毒与SPFMV抗血清起阳性反应。     

高效价甘薯羽状斑驳病毒抗血清的制备

用嫁接方法将甘薯羽状斑驳病毒（ＳＰＦＭＶ）接种到Ｉ．ｓｅｔｏｓａ上扩繁,以０．２ｍｏｌ／ＬｐＨ７．２ＰＢＫ缓冲液、垫层差速离心、蔗糖密度梯度离心提取纯化ＳＰＦＭＶ。纯化的ＳＰＦＭＶＯＤ２６０／２８０的比值为１．２５。将纯化的ＳＰＦＭＶ免疫家兔制备抗血清,在环状沉淀和微量沉淀试验中,用提纯病毒测定抗血清的效价均为１：４０９６;以ＳＰＦＭＶ－ＩｇＧ为第一抗体,应用Ｄｏｔ－ＥＬＩＳＡ对甘薯和Ｉ．ｓｅｌｏｓａ叶片中的ＳＰＦＭＶ分别作了测定。     

Aspects of resistance to sweet potato virus disease in sweet potato

In field trials during the first and the second rainy season of 1996 in Uganda, whiteflies were similarly abundant and aphids were absent on three clones of sweet potato (NIS-93–63, cv. Tanzania and cv. New Kawogo) although the three clones differed considerably in their resistance to sweet potato virus disease (SPVD), a complex disease resulting from infection by both the aphid-borne sweet potato feathery mottle virus (SPFMV) and the whitefly-borne sweet potato chlorotic stunt virus (SPCSV). This suggests that vector resistance does not determine the relative SPVD resistance of these genotypes. SPFMV alone had only a low virus titre in sweet potato cvs Tanzania and New Kawogo, became increasingly difficult to detect in plants of these cultivars and was seldom acquired by aphids. However, this resistance to SPFMV was not apparent in plants which were also infected with SPCSV. Plants then had a high SPFMV titre, appeared unable to eliminate SPFMV and provided good sources for aphids to acquire it.     

Apparent absence of viruses in most symptomless field-grown sweet potato in Uganda

Heat tolerance of groundnut (Arachis hypogaea L.) genotypes was evaluated by solute leakage and chlorophyll fluorescence techniques in heat-hardened and non-hardened plants. To determine the appropriate hardening treatment, 1-month-old plants of two groundnut genotypes, ICGV 86707 and Chico were conditioned at five combinations of hardening (37°C) and non-hardening (30°C) air temperatures over a 5-day period. Heat injury, was assessed through measurements of electrolyte leakage after stressing leaf discs to 55°C for 15 min. The relative injury was significantly influenced by the conditioning temperatures and by the temperature during 24 h prior to measurement if those involved non-hardening conditions. Relative injury and chlorophyll fluorescence were measured after stressing leaves of six genotypes at a range of temperatures between 49°C and 55°C. Significant genotype × hardening treatment interactions were observed in relative injury and chlorophyll fluorescence. Chico was susceptible to heat stress, the relative injury test identified ICGV 86707 as tolerant, and the chlorophyll fluorescence test identified ICGV 86707 as tolerant under hardened conditions and ICGV 87358 as tolerant when non-hardened. When expressed as percentage of control values, the relative injury and chlorophyll fluorescence measurements over the 49–53°C stress temperature range were strongly correlated. Chlorophyll concentrations were increased by hardening in all genotypes except Chico. In Chico, chl_b concentration was decreased and the chl_a/b ratio increased by hardening, and chlorophyll concentrations were correlated with chlorophyll fluorescence parameters. Chlorophyll concentration may therefore provide an alternative means of screening for heat tolerance.     

福建甘薯病毒病病原鉴定及主要病毒多样性

【背景】病毒病是甘薯的一种重要病害,给甘薯生产带来了严重的经济损失,而生产中甘薯病毒病病原种类复杂多样。【目的】明确福建甘薯病毒病种类、分布及流行,对主要病毒进行多样性分析。【方法】从福建主要甘薯种植区采集病毒病样品,利用PCR/RT-PCR的方法对采集的样品进行病原检测,获得病毒序列,利用MEGA 6.0构建系统进化树进行遗传分析。【结果】从福建7个甘薯产区鉴定12种甘薯病毒,包括9种RNA病毒:甘薯羽状斑驳病毒(Sweet potato feathery mottle virus,SPFMV)、甘薯褪绿矮化病毒(Sweet potato chlorotic stunt virus,SPCSV)、甘薯G病毒(Sweet potato virus G,SPVG)、甘薯C病毒(Sweet potato virus C,SPVC)、甘薯2号病毒(Sweet potato virus 2)、甘薯褪绿斑病毒(Sweet potato chlorotic fleck virus,SPCFV)、甘薯潜隐病毒(Sweet potato latent virus,SPLV)、甘薯轻型斑点病毒(Sweetpotatomildspeakingvirus,SPMSV)、黄瓜花叶病毒(Cucumber mosaic virus,CMV),3种DNA病毒:甘薯卷叶病毒(Sweet potato leaf curl virus,SPLCV),甘薯无症状1号病毒(Sweet potato symptomless virus 1,SPSMV-1),甘薯杆状DNA病毒B (SPBV-B)。SPFMV、SPCSV、SPVG和SPLCV检出率最高,分别为50.28%、41.90%、35.75%和24.58%,CMV检出率最低,为2.79%,未检测到甘薯C-6病毒(SweetpotatoC-6)和甘薯轻型斑驳病毒(Sweetpotatomild mottle virus,SPMMV)。福建甘薯主要以2-6种病毒复合侵染为主,单一侵染率占14.39%,2种以上复合侵染占85.61%。福建SPFMV分离物存在EA、O和RC3种株系,SPCSV分离物存在WA1种株系,未发现EA株系,甘薯卷叶病毒分属于2个不同的株系群。【结论】福建甘薯病毒种类多样,以复合侵染为主,且存在多种株系,遗传结构复杂。     

The Effect of the Sequence of Infection of the Causal Agents of Sweet Potato Virus Disease on Symptom Severity and Individual Virus Titres in Sweet Potato cv. Beauregard

Sweet potato virus disease (SPVD) is caused by dual infection of plants with Sweet Potato Feathery Mottle Virus (SPFMV) and Sweet Potato Chlorotic Stunt Virus (SPCSV). Because SPFMV and SPCSV are transmitted by aphids and whiteflies, respectively, infection in nature occurs independently rather than simultaneously. To investigate the effect of consecutive infection on symptom development and individual virus titres, plants infected with a single virus were later inoculated with the second virus. Symptoms were significantly more severe in plants infected with SPCSV followed by SPFMV compared to plants infected with SPFMV followed by SPCSV. Virus titres were not significantly different for SPCSV, but SPFMV titres, in plants infected with SPCSV followed by SPFMV, were significantly higher than all other treatments. The results indicate that the sequence of infection of sweetpotato plants with the causal agents of SPVD influence the severity of symptoms and SPFMV titres in SPVD affected plants.     

湖南甘薯种质资源曲叶病毒检测分析初报

本研究依托\"第三次全国农作物种质资源普查与收集行动\",利用巢式PCR(Nested PCR)检测技术,对从湖南各地区采集的甘薯种质资源进行甘薯曲叶病毒的调查、检测、统计与分析,获得该地区甘薯种质资源曲叶病毒的感染和分布情况。对收集的246份甘薯种质资源进行了甘薯曲叶病毒病症状的调查,记录了每份种质资源的田间生长特性;建立了一种甘薯曲叶病毒巢式PCR检测技术,该技术相对其他技术具有特异性强、灵敏度高、检测通量大、检测成本低的特点。利用建立的巢式PCR检测技术对选取的样品进行甘薯曲叶病毒检测,分析检测结果发现:(1)巢氏PCR共检测出14份甘薯种质资源感染甘薯曲叶病毒,根据病毒基因测序结果分析湖南省至少存在2种曲叶病毒株系。(2)田间调查共发现8份甘薯种质资源的叶片具有甘薯曲叶病毒病典型的卷曲症状,但是其中仅有4份资源与曲叶病毒巢氏PCR检测结果一致;另外4份资源虽然具有明显的卷叶现象但是未检测出曲叶病毒。(3)曲叶病毒检测呈阳性的14份甘薯种质资源分别来源于邵阳市、长沙市、永州市和株洲市4个地区,占种质资源总数的5.7%;4个地区甘薯种质资源的病毒感染率分别为17.6%、14.5%、7.1%和6.7%;全省范围内的种质资源染病情况具有较大的地域差异性;综合甘薯种植情况和地理环境分析,商品薯的跨区域流通和农民自留种的种植习惯是影响甘薯病毒传播的主要因素。本研究首次利用巢式PCR技术对湖南地区甘薯曲叶病毒进行检测和调查,为甘薯种质资源的保存、繁殖、鉴定与利用提供了重要的技术支撑,也为湖南地区甘薯曲叶病毒侵染情况及相关的分子生物学研究提供了数据参考。     

Purification and properties of closterovirus-like particles associated with a whitefly-transmitted disease of sweet potato

A virus causing sunken veins on ‘Georgia Jet’ sweet potato, and yellow brittle leaves and stunting on Ipomoea setosa, was purified and a specific antiserum was prepared. Flexuous particles with a normal length of 850 nm and a diameter of 12 nm with an open helical structure typical of closteroviruses were observed. The virus particle protein has an apparent mol. wt of c. 34 kD. Double-stranded RNA isolated from SPSVV-infected I. setosa and subjected to electrophoresis in agarose consisted of one major band with an estimated M_r of 10.5 kbp and two minor bands with M_r of 9.0 and 5.0 kbp. Fibril-containing vesicles in phloem cells were observed in ultrathin sections of infected leaf tissues. The virus was transmitted by the whitefly Bemisia tabaci in a semi-persistent manner and by grafting, but not mechanically. The virus could be transmitted to various Ipomoea species, to Nicotiana clevelandii, N. benthamiana and Amaranthus palmeri. The virus did not react with an antiserum to lettuce infectious yellows virus. Based on particle morphology, serology and symptom expression, the virus appears unique and different from all other reported whitefly-transmitted closteroviruses. We propose it be named “sweet potato sunken vein virus” (SPSVV).     

Sweet Potato Virus Disease in Sub-Saharan Africa: Evidence that Neglect of Seedlings in the Traditional Farming System Hinders the Development of Superior Resistant Landraces

Sweet potato virus disease (SPVD) occurs in sweet potato at all localities on the perimeter of Lake Victoria areas surveyed in Uganda and Tanzania, and was particularly common in Kagera District in Tanzania and in Rukungiri District in Uganda. All fields were planted with landraces and the most important control practices, as perceived by farmers, were the planting of cuttings derived from only symptomless parents and destroying diseased plants. Although SPVD-resistant landraces were available, they were perceived by most farmers to have poor and late yields. Most farmers considered that their greatest need was new, more acceptable, SPVD-resistant genotypes. Few farmers had seen either sweet potato seeds (15%) or sweet potato seedlings (11%) and, of those that had, most had ignored them. The lack of seedlings and their neglect by farmers is likely to be hindering the evolution of more acceptable, SPVD-resistant landraces, and is probably responsible for SPVD being a long-term disease problem.     

Synergistic interactions of begomoviruses with Sweet potato chlorotic stunt virus (genus Crinivirus) in sweet potato (Ipomoea batatas L.)

Three hundred and ninety‐four sweet potato accessions from Latin America and East Africa were screened by polymerase chain reaction (PCR) for the presence of begomoviruses, and 46 were found to be positive. All were symptomless in sweet potato and generated leaf curling and/or chlorosis in Ipomoea setosa. The five most divergent isolates, based on complete genome sequences, were used to study interactions with Sweet potato chlorotic stunt virus (SPCSV), known to cause synergistic diseases with other viruses. Co‐infections led to increased titres of begomoviruses and decreased titres of SPCSV in all cases, although the extent of the changes varied notably between begomovirus isolates. Symptoms of leaf curling only developed temporarily in combination with isolate StV1 and coincided with the presence of the highest begomovirus concentrations in the plant. Small interfering RNA (siRNA) sequence analysis revealed that co‐infection of SPCSV with isolate StV1 led to relatively increased siRNA targeting of the central part of the SPCSV genome and a reduction in targeting of the genomic ends, but no changes to the targeting of StV1 relative to single infection of either virus. These changes were not observed in the interaction between SPCSV and the RNA virus Sweet potato feathery mottle virus (genus Potyvirus), implying specific effects of begomoviruses on RNA silencing of SPCSV in dually infected plants. Infection in RNase3‐expressing transgenic plants showed that this protein was sufficient to mediate this synergistic interaction with DNA viruses, similar to RNA viruses, but exposed distinct effects on RNA silencing when RNase3 was expressed from its native virus, or constitutively from a transgene, despite a similar pathogenic outcome.     

The incidence of sweet potato virus disease and virus resistance of sweet potato grown in Uganda

Sweet potato virus disease (SPVD) was common (25–30% average incidences), and farmers recognised it as an important disease, in sweet potato crops in southern Mpigi, Masaka and Rakai Districts in Uganda, but SPVD was rare in Soroti and Tororo Districts. Whiteflies, which are the vector of sweet potato chlorotic stunt crinivirus (SPCSV) a component cause of SPVD, were correspondingly common on sweet potato crops in Mpigi and rare on crops in Tororo. However, aphids, which are the vectors of sweet potato feathery mottle potyvirus (SPFMV), the other component cause of SPVD, were not found colonising sweet potato crops, and itinerant alate aphids may be the means of transmission. Different sweet potato cultivars were predominant in the different districts surveyed and four local cultivars obtained from Kanoni in S. Mpigi, where whiteflies and SPVD were common, were more resistant to SPVD than four cultivars from Busia in Tororo District, where whiteflies and SPVD were rare. However, nationally released cultivars were even more resistant than the local cultivars from Kanoni. Yield results and interviews with farmers indicated that farmers in S. Mpigi were making compromises in their choice of cultivars to grow, some key factors being SPVD susceptibility, and the yield, taste, and marketability, duration of harvest and in-ground storability of the storage roots. These compromises need to be included in an assessment of yield losses attributable to SPVD.     

云南甘薯病毒的检测及主要病毒的多样性分析

[目的]明确云南甘薯病毒的种类,并对主要病毒进行遗传多样性分析.[方法]利用PCR/RT-PCR技术,对采自云南16个县、市的279个甘薯样品进行扩增、测序,对所得序列应用分子生物学软件MEGA 5进行系统发育分析.[结果]除普洱和祥云的样品中未检测到任何病毒外,其余14个县、市的123个甘薯样品中共检测到甘薯褪绿斑病毒(SPCFV)、甘薯羽状斑驳病毒(SPFMV)、甘薯卷叶病毒(SPLCV)、甘薯C病毒(SPVC)、甘薯G病毒(SPVG)和甘薯病毒2号(SPV2)等6种病毒.其中SPVG的检出率最高,达39.1％,为云南甘薯病毒的优势种,SPFMV和SPVC的检出率分别为26.9％和24.7％,而SPLCV检出率最低,仅为0.4％.在所检测的样品中未发现甘薯褪绿矮化病毒(SPCSV)和甘薯轻斑驳病毒(SPMMV).云南甘薯病毒多数为2-5种病毒复合侵染,占总样品数的31.9％,其中2-3种病毒复合侵染现象最为常见,单一病毒侵染占总样品数的12.2％.检出率比较低的SPCFV、SPLCV和SPV2未发现单独侵染现象.[结论]云南甘薯上发生的SPFMV分离物存在EA株系和O株系,未发现RC株系,另有两个分离物同EA、O、RC之间的亲缘关系均较远,有可能是一个新的株系;SPVC和SPVG分离物均可分为3个不同的组,大部分SPVG云南分离物属于Ⅰ组.     

Virus content of seed potato stocks produced in a unique seed potato production scheme

Western Australia has a unique seed potato production scheme which has remained virtually unchanged for more than 60 years, consisting of summer plantings of predominantly one cultivar in wind-exposed coastal swamplands. No rotation is used and the scheme relies on natural winter flooding and 'grazing' by sheep to eliminate unharvested tubers. Stocks are recycled every year with only limited inputs of pathogen-tested seed tubers in recent times. Virus spread in the crop is controlled by selecting large tubers for planting, roguing, aphicide application and growing season inspections. Potato viruses X and S were commonly detected in old seed stocks produced by this scheme attaining 100% infection in some. Both viruses were less frequently found in newly introduced seed stocks. By contrast, potato virus Y was never detected and potato leaf roll virus rarely found.