Dissemination of rhizomania by soil,beet seeds and stable manure

Polymyxa betae, the vector of beet necrotic yellow vein virus (BNYVV), (the causal agent of rhizomania of sugar-beet), forms cystosores which are very persistent and might be dispersed by soil, beet seeds, plant material and stable manure. Research has been carried out into the risk of dissemination; relative importance was not determined. Inoculation with diseased soil in a field caused rhizomania in sugar-beets within one year. This implies that even small amounts of soil adhering to plant roots constitute a potential danger. Direct transmission of BNYVV by sugar-beet seeds could not be demonstrated, but, after processing and cleaning seed lots originating from infested fields, the seed waste proved to be contaminated. Cystosores ofP. betae and, to a lesser extent, BNYVV could pass through the intestine of sheep in fodder experiments carried out with heavily infested sugar-beet tails.Samenvatting De vector van het bieterhizomanievirus,Polymyxa betae, vormt zeer persistente ruststructuren (cystosoren) die verspreid worden met grond, bietezaad, plantmateriaal en stalmest.Onderzoek is uitgevoerd naar de risico's van verspreiding, maar door het ontbreken van kwantitatieve methoden kon de relatieve belangrijkheid niet worden vastgesteld.Wanneer een gezond perceel werd besmet met geïnfecteerde grond (20 ng dm^–3 op bouwvoor), werd binnen één jaar aantasting door rhizomanie waargenomen. Dit wijst erop dat geringe hoeveelheden grond, die meekomen met wortelmateriaal van plantgoed, een potentieel gevaar vormen.Directe overdracht van het bieterhizomanievirus door bietezaad kon niet worden aangetoond, maar na het schonen en bewerken van zaadpartijen afkomstig van zieke percelen bleek dat schoningsafval en in het bijzonder de grondfractie daarvan, wel was besmet.Cystosoren vanP. betae en in mindere mate het bieterhizomanievirus konden het maag-darmkanaal van schapen passeren, hetgeen werd aangetoond in enkele voederproeven, uitgevoerd met zwaar besmette suikerbietestaartjes.     

利用PCR-SSCP对新疆甜菜坏死黄脉病毒RNA2变异的研究

应用反转录-聚合酶链式反应(RT-PCR)和单链构象多态性(SSCP)分析技术,对新疆不同地区的甜菜坏死黄脉病毒(BNYVV)RNA2的区间进行分析,12个BNYVV分离物和美国的BN-TX及我国黑龙江的He分离物通过RT-PCR扩增后都能得到一段590bp左右大小的片段;通过SSCP分析,12个分离物既不同于美国的BN-TX分离物,也不同于黑龙江的He分离物,可分为4个变异类型,S1和S2归为Ⅰ类,T3、T6、T7和T8归为Ⅱ类,K1、K2、K4和K5归为Ⅲ类,Q1和Q2归为Ⅳ类,初步明确了新疆BNYVV分离物存在着分化,而且有明显的地域分布性。     

甜菜丛根病研究概况

从引发甜菜丛根病的致病病毒BNYVV、传播介体P.betae及环境影响因素等方面,对甜菜感染丛根病后的病症、鉴定、生理生化反应及其防治等研究进行了全面的综述。     

Ecological aspects of transgenic sugar beet: transfer and expression of herbicide resistance in hybrids with wild beets

Summary An increasing number of genetically engineered cultivars of several crops is being experimentally released into the environment. In future, crops with new transgenic traits will probably play an important role in agricultural practice. The long-term effect of transgenes on community ecology will depend on the distribution and establishment of transgenic plants in the wild, on the sexual transfer of their new genes to the environment and on the potential ecological impact of the transgenic trait. The starting point was the use of transgenic sugar beet lines, Beta vulgaris subspec. vulgaris var. altissima DÖLL (Helm 1957), with transgenes coding for rhizomania and herbicide (BASTA^®) resistance. The first two questions to answer were: Can the transgenes be transferred via pollen to wild beets, Beta vulgaris subspec. maritima (L.) ARCANG. or cultivated relatives such as red beet or spinach beet and are they expressed in the hybrids? Can transgenes be monitored in young Beta vulgaris-hybrids? The experimental transfer of transgenes was conducted in 1993 at a field location in northern Germany. The beets were hand-pollinated with transgenic pollen. In a non destructive biotest, the hybrid seedlings were tested for herbicide resistance. Transgenic plants showed no noxious phenotypic effects whereas control plants developed leaf necroses. All herbicide resistant hybrids within the biotest were assumed to be transgenic.     

Horizontal spread of beet necrotic yellow vein virus in soil

Horizontal dispersal of beet necrotic yellow vein virus (BNYVV) by means of viruliferous zoospores ofPolymyxa betae was studied in greenhouse experiments. BNYVV was not detected in roots of sugar beet plants grown in silver sand for 4 weeks at a root-free distance of 5 cm from eitherP. betae- and BNYVV-infected plants or BNYVV-infested soil. Spread of BNYVV from inoculum sources in the field was studied in the absence and presence of tillage practices. Active dispersal in combination with root growth from and towards point sources of inoculum contributed only little to horizontal dispersal of viruliferous inoculum and spread of disease during the season, as determined for one soil type, two different years and in the absence of tillage and tread. In the second beet crop after application of inoculum to whole field plots, more BNYVV-infected plants were detected at 2 m than at 8 m distance from the infested plots in the tillage direction. In the third year, disease incidence at 8 m was high and equivalent to that at 2 m.     

甜菜坏死黄脉病毒（BNYVV）的快速检测技术及在抗病育种上的应用

应用ＢＮＹＶＶ抗体球蛋白，建立了快速检测ＢＮＹＶＶ的间接酶跌免疫吸附技术（Ｉｎｄｉｒｅｃｔ－ＥＬＬＳＡ），该法检测含抗原材料仅需４．５小时，较国际通用程序缩短２０余小时。主要程序包括：抗原经３７℃包被２小时后，加ＢＮＹＶＶ抗体球蛋白ＩｇＧ，３７℃孵育１小时，然后加过氧化物酶标记的单抗兔ＩｇＧ，３７℃孵育１小时，最后加底物液邻笨二胺，常温下反应１５～３０分钟，应用该法对采集的４份标样进行测定，其中两份测出含有ＢＮＲＶＶ，对不同抗感丛根病性品种（系）经室内病土盆栽或病田栽培，调查病情并取样测定根部ＢＮＹＶＶ含量，结果表明。品种间存在显著差异，ＢＮＹＶＶ含量、病情与品种（系）抗病性表现基本一致。     

Effect of conditions during storage of infested soil on infection of bait plants by Polymyxa betae and beet necrotic yellow vein virus

Infectivity of resting spores ofPolymyxa betae in soil stored air-dry or moist was determined by assessing infection of bait plants that were exposed to the soil. Storage of soil under air-dry conditions at room temperature resulted in a delayed onset of germination of resting spores compared to germination in soil stored under moist and cool conditions, as inferred from the infection of the bait plants. Bait plants had to be exposed for more than 12 h to flooded infested soil before germination and infection had occurred. However, when soil was prewetted for 24 h before exposing bait plants, germination, infection and transmission of beet necrotic yellow vein virus (BNYVV) were accomplished within 12 h, but only with the moistly stored soil. When resting spores isolated from roots were stored for 4 and 8 weeks under dry conditions at 22°C, germination of viruliferous spores, as measured by detection of BNYVV in bait plants exposed for 48 h to the spores, was less than that of spores stored in moist soil at 22°C. Approximately 100% of bait plants were infected after exposure to resting spores that were frozen in demineralized water or stored cool (5°C) in water or moist soil for 42 weeks. Air-dry cool storage for 42 weeks resulted in a low percentage of infection. Storage conditions of soil influence the results of bioassays for detection of rhizomania when short baiting periods are applied, whereas differences in infectivity were not detected using a bioassay with long duration.     

甜菜多粘菌传带甜菜坏死黄脉病毒的细胞定位研究

 利用砂培体系继代培养不同病区甜菜多粘菌(Polymyxa betae),经酶联检测,分离得到2个带毒率高的分离株N,HR₁₂。应用甜菜坏死黄脉病毒(BNYVV)抗血清和免疫金标记技术分析了甜菜根中P.betae不同发育阶段与病毒的关系。在初生原质体、游动孢子囊以及未成熟的游动孢子中观察到被金颗粒标记的病毒粒子,在休眠孢子外围也观察到金标记的病毒粒子,但在休眠孢子内未直接观察到病毒粒子,只是在其内壁及液泡中常见有标记上的金颗粒。     

Effect of sugar beet cultivars with different levels of resistance to beet necrotic yellow vein virus on transmission of virus byPolymyxa betae

The effect of resistance of sugar beet cultivars to beet necrotic yellow vein virus (BNYVV) on virus content of resting spore clusters of the vectorPolymyxa betae was studied in controlled environments and in naturally infested fields. The total number of resting spore clusters formed in roots of a partially resistant and a susceptible cultivar did not differ when assessed 6 and 12 weeks after inoculation with viruliferous resting spores. Transmission experiments showed that in partially resistant plants, having a low virus content in the roots, the population of resting spores formed was less viruliferous than that in susceptible plants with a high virus content. Consequently, growing a resistant cultivar can be expected to delay the build-up of virus inoculum in soil.In a trial field sampled in 1991, the inoculum potential of BNYVV (most probable number of viruliferousP. betae propagules) in soil was lower after growing a partially resistant cultivar than after growing a susceptible one. On the other hand, in four sites sampled in 1990, inoculum potential in soil was hardly increased by growing sugar beet and was not significantly affected by the cultivar grown.     

Pathogenetic roles of beet necrotic yellow vein virus RNA5 in the exacerbation of symptoms and yield reduction,development of scab-like symptoms,and Rz1-resistance breaking in sugar beet

Beet necrotic yellow vein virus (BNYVV) generally has a four-segmented positive-sense RNA genome (RNAs 1–4), but some European and most Asian strains have an additional segment, RNA5. This study examined the effect of RNA5 and RNA3 on different sugar beet cultivars using a Polymyxa-mediated inoculation system under field and laboratory conditions. In field tests, the degree of sugar yield served as an index for assessing the virulence of BNYVV strains. Japanese A-II type isolates without RNA5 caused mostly 15%–90% sugar yield reductions, depending on the susceptibility of sugar beet cultivars, whereas the isolates with RNA5 induced more than 90% yield losses in the seven susceptible cultivars, but small yield losses in one Rz1-resistant and Rizor cultivars. However, a laboratory-produced isolate containing RNA5 but lacking RNA3 caused higher yield losses in Rizor than in susceptible plants, and induced scab-like symptoms on the root surface of both susceptible and resistant plants. In laboratory tests, A-II type isolates without RNA5 had low viral RNA accumulation levels in roots of Rizor and Rz1-resistant plants at early stages of infection, but in the presence of RNA5, viral RNA3 accumulation levels increased remarkably. This increased RNA3 accumulation was not observed in roots of the WB42 accession with the Rz2 gene. In contrast, the presence of RNA3 did not affect RNA5 accumulation levels. Collectively, this study demonstrated that RNA5 is involved in the development of scab-like symptoms and the enhancement of RNA3 accumulation, and suggests these characteristics of RNA5 are associated with Rz1-resistance breaking.