福州和成都竹花叶病毒的RT-PCR法检测

 竹花叶病毒(Bamboo mosaic virus, BaMV)是马铃薯X病毒属唯一携带有卫星RNA的成员,目前已经在巴西、美国以及中国台湾等地的竹类栽培区产生危害,严重影响竹材的经济价值,而在中国大陆还不曾有相关报道。根据GenBank上报道的BaMV和其伴随卫星RNA(satBaMV)序列以及未公布的序列分别设计了1对特异性引物,在优化RT-PCR条件的基础上,成功建立了BaMV的RT-PCR检测方法。 CpC-F/R用于扩增部分BaMV-CP序列(527 bp),SaC-F/R用于扩增satBaMV部分序列(472 bp)。把所建立的方法用于检测分别采自成都和福州的不同品种竹子病叶,结果均检测出了BaMV和satBaMV,而无症样品未得到任何产物。本研究在基因水平上为BaMV的检测提供了快速、准确、灵敏的新体系,为我国竹类栽培过程中竹花叶病毒的检测和防治提供了有效手段。     

生物素标记cDNA探针杂交检测梨树上3种潜隐病毒研究

 本研究合成了苹果茎沟病毒(ASGV)、苹果褪绿叶斑病毒(ACLSV)和苹果茎痘病毒(ASPV)的生物素标记cDNA探针,对斑点杂交和免疫印迹杂交检测这3种病毒的效果进行了分析。以含ACLSV和ASGV克隆片段的大肠杆菌菌液为样品时,斑点杂交检测灵敏度分别为80 cfu/μL和50 cfu/μL。以离体培养砂梨植株为材料,采用斑点杂交法检测砂梨离体培养植株粗提液中的3种病毒,均产生强的杂交信号,且特异性好。比较斑点杂交和ELISA检测病毒含量相对较低的热处理再生植株中ASGV和ACLSV,结果表明斑点杂交具有较高的灵敏度。组织印迹杂交检测砂梨离体植株ASGV和ACLSV的结果显示,这2种病毒在离体植株的各部位均有分布,自基部至茎尖各部位印迹均产生很强的杂交信号。     

Evaluation of a DNA probe for the detection of Erwinia herbicola strains pathogenic on Gypsophila paniculata

A 7.5-kb DNA fragment carrying genes for indole acetic acid biosynthesis in Erwinia herbicola pv. gypsophilae was used as a DNA probe to detect gall-forming E. herbicola strains. A quick colony hybridization procedure was developed to detect E. herbicola pv. gypsophilae in cuttings of gypsophila, and was compared with ELISA and pathogenicity tests. The sensitivity of the colony hybridization procedure was sufficient to detect less than 100 colony-forming units after enrichment culture. In mixed cultures, with saprophytes associated with the gypsophila plant, about 10⁴ CFU/ml of the pathogen were detectable. The colony hybridization is specific to gall-forming E. herbicola strains, and is relatively easy to perform. The advantages of using the colony hybridization procedure for practical purposes, compared with ELISA and pathogenicity tests, are discussed.     

Contribution of host plant resistance and geographic distance to the structure of Potato virus Y (PVY) populations in pepper in northern Tunisia

The genetic structure of Potato virus Y (PVY) populations was investigated in naturally-infected pepper ( Capsicum annuum ) fields, collected at eight different localities in northern Tunisia, where 23% of the sampled plants were homozygous for the pvr2¹ recessive resistance allele, while the other plants carried the dominant susceptibility allele pvr2⁺ . Restriction fragment length polymorphism analysis at three PVY genome segments revealed a high level of viral diversity, with a majority of cases showing co-infection of individual plants by several PVY haplotypes and a strong genetic differentiation of viral populations collected in the different localities. Geographic distances affected the differentiation of PVY populations and isolation by distance among these populations was significant. However, the occurrence of the pvr2¹ resistance allele did not contribute to the structure of viral populations, suggesting that the virulence properties of the virus did not significantly affect its fitness. Consequently, greater deployment of the pvr2¹ gene would probably not be a suitable strategy to control PVY, and other resistance genes should be preferred.     

Some properties of a virus-like agent found in Brachypodium sylvaticum in the United Kingdom

A spherical virus–like agent ($$32 nm in diameter) was isolated from a plant of Brachypodium sylvaticum (Huds.) Beauv. growing in a botanic garden in England and showing yellow streaks in the leaves. The agent was readily purified and sedimented as a single component in sucrose density rate gradients. The particles had a sedimentation coefficient at infinite dilution of $$122S and a buoyant density of 1.35 g/cm³ in CsCl and 1·33 in CS₂SO₄. The particles were stable at acid pH but above pH 7·0 in the presence of EDTA dissociated. A protein having a major polypeptide with a molecular weight of $$3·76 × 10⁴ and a species of single stranded RN A with a MW of 1·67 × 10⁶ were detected in the particles. The agent was not transmitted by manual inoculation, by the insects Myzus persicae Sulzer, Rhopalosiphum padi L. or Nephotettix virescens Distant, through soil by leakage from roots or by seed. The particles had physicochemical properties in common with tombus– and sobemoviruses but were not serologically related to 10 members of these groups or to 57 other small spherical RNA plant viruses.     

TRANSLOCATION OF 14C-ASSIMILATES AND 3-AMINO-1,2,4-TRIAZOLE AND ITS METABOLITES IN AGROPYRON REPENS

Summary. Translocation of 3-amino-1,2,4-triazole-5-¹⁴C (¹⁴C-aminotriazole) was compared to that of ¹⁴C-assimilates in couch grass ( Agropyron repens (L.) Beauv.) at three different growth stages.
Assimilates of ¹⁴CO₂ were translocated from the treated shoot to other shoots and rhizomes at the 2–3-leaf and 3–4-leaf stages of development. Much less labelled material was translocated into untreated shoots at the 5-leaf stage. More ¹⁴C-assimilates were translocated to the roots than to untreated shoots at all developmental stages. The translocation patterns of ¹⁴C-aminotriazole and ¹⁴C-assimilates were similar.
Two metabolites, A and B, were formed from ¹⁴C-aminotriazole, which chromatographed identically to previously described metabolites in Cirsium arvense (L.) Scop. A was further metabolized into B. Labelled aminotriazole and its two metabolites were translocated throughout the plants. Metabolite A was phytotoxic when concentrated and re-applied to couch grass, but its properties were not those of Unknown II from Cirsium arvense. They were the same as those of Unknown III. Whether or not metabolite A and Unknown III are identical was not established.
Migration des substances assimilables marquées au ¹⁴ C, du 3 amino-1,2,4-triazole et de ses métabolites chez Agropyron repens     

Uptake and metabolism of hexazinone in Rubus hispidus L. and Pyrus melanocarpa (Michx.) Willd

Rooted cuttings of Pyrus melanocarpa (Michx.) Willd. had a 3.5-fold greater tolerance to soil-applied hexazinone than those of Rubus hispidus L. in a greenhouse trial. R. hispidus accumulated four times more ¹⁴C-label in the foliage following root uptake of ¹⁴C-hexazinone than P. melano-carpa . Here, the greater uptake and susceptibility of R. hispidus was related to its greater root:fol-iage (weight) ratio compared to the tolerant P. melanocarpa . However, in whole plant metabolism studies employing younger plants there were no differences in ¹⁴C accumulation in the leaves. Here ¹⁴Chexazinone was converted to a number of hydroxylated and/or demethylated triazinone metabolites in both species following vacuum infiltration into leaf disks and root sections, or following root uptake in whole plants. A major difference in metabolism between the two species was the greater formation of the mono demethylated metabolite, B, [3-cyclohexyl-6-methylamino-l-methyl-l,3,5-triazine-2,4-dione] in P. melanocarpa which may also contribute to its greater tolerance. A loss of total ¹⁴Clabel from all plant parts with time may reflect cleavage of the ¹⁴C-ring-labelled herbicide.     

竹花叶病毒浙江麻竹分离物全基因组序列及siRNA分析

正已知有3种病毒可在自然条件下侵染竹类植物,即竹花叶病毒(bamboo mosaic virus,BaMV)~[1]、樱桃坏死锈斑驳病毒(cherry necrotic rusty mottle virus,CNRMV)和苹果茎沟病毒(apple stem grooving virus,ASGV)~[2,3]。其中,BaMV是最早在巴西的金竹(Bambusa vulgaris Cv.)和孝顺竹     

Root exudation of diclofop-methyl and triasulfuron from foliar-treated durum wheat and ryegrass

In this study, we evaluated the release of diclofop-methyl and triasulfuron from the roots of foliar-treated ryegrass and wheat. The study with ¹⁴C-diclofop-methyl indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass. No root exudation from ¹⁴C-diclofop-methyl-treated wheat plants was observed, while 20 days after treatment (DAT) 0.2–0.9% of radioactivity absorbed by ryegrass was found exuded in the growing medium. Root exudation was stimulated three to six times by the presence of untreated wheat or ryegrass sharing the growing medium with diclofop-methyl-treated ryegrass. No subsequent uptake of exuded radiolabel by untreated plants (ryegrass or wheat) in the same pot with ¹⁴C-diclofop-methyl-treated ryegrass was observed. The study with ¹⁴C-triasulfuron indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass and also into the growing medium. By 20 DAT, 0.5–4.2% of radioactivity absorbed by wheat or ryegrass was found exuded in the growing medium. The presence of untreated plants (wheat or ryegrass) in the same pot as triasulfuron-treated ryegrass or wheat induced exudation seven to 32 times more. The study also revealed a subsequent uptake of exuded compounds by untreated wheat or ryegrass sharing the medium of ¹⁴C-triasulfuron-treated plants. This study has demonstrated for the first time that the root exudation of exogenous compounds can be related to plant arrangement in pots. The implication is that herbicide root exudation and transfer, a form of allelopathy, could be significant in the field. A precise estimation of environmental fate, unexpected ecological side effects and residual activity of herbicides may require quantification of such exudation.     

Visual and PCR assessment of light leaf spot (Pyrenopeziza brassicae) on winter oilseed rape (Brassica napus) cultivars

Methods to assess light leaf spot ( Pyrenopeziza brassicae ) on winter oilseed rape cultivars were compared in laboratory, controlled-environment and field experiments. In controlled-environment experiments with seedling leaves inoculated at GS 1,4, the greatest differences in percentage area affected by P. brassicae sporulation were observed with inoculum concentrations of 4 × 10³ or 4 × 10⁴ spores mL⁻¹, rather than 4 × 10² or 4 × 10⁵ spores mL⁻¹, but older leaves had begun to senesce before assessment, particularly where they were severely affected by P. brassicae . In winter oilseed rape field experiments, a severe light leaf spot epidemic developed in 2002/03 (inoculated, September/October rainfall 127·2 mm) but not in 2003/04 (uninoculated, September/October rainfall 40·7 mm). In-plot assessments discriminated between cultivars best in February/March in 2003 and June in 2004, but sometimes failed to detect plots with many infected plants (e.g. March/April 2004). Ranking of cultivar resistance differed between seedling experiments done under controlled-environment conditions and field experiments. The sensitivity of detection of P. brassicae DNA extracted from culture was greater using the PCR primer pair PbITSF/PbITSR than using primers Pb1/Pb2. P. brassicae was detected by PCR (PbITS primers) in leaves from controlled-environment experiments immediately and up to 14 days after inoculation, and in leaves sampled from field experiments 2 months before detection by visual assessment.     

以18S rRNA为内参照的多重RT-PCR检测3种百合病毒

 本研究对多重PCR体系各成分和循环参数进行了摸索和优化,建立了以18SrRNA为内参照的同时检测3种百合病毒的多重RT-PCR体系,所检测的3种病毒是黄瓜花叶病毒(CMV)、百合斑驳病毒(LMoV)和百合无症病毒(LSV)。它们为侵染我国百合的主要病毒。在RT反应体系中加入3种病毒和18S rRNA的特异性反向引物的混合物,使反应体系中各反向引物终浓度均为0.5μmol/L,反转录酶(AMV)反转录合成各病毒和18SrRNA的互补第一链cDNAs。多重RT-PCR条件实验显示:将标准RT-PCR体系中的Taq HS DNA聚合酶量改为0.100U/μL,Mg²⁺浓度改为4.0mmol/L,各引物浓度选择0.2μmol/L,那么25个循环反应以上就能在一个反应管中以18SrRNA为内参照同时检测百合中的3种常见病毒。用该体系检测了10个百合样品,同时与³²P同位素标记膜杂交检测作对照,结果显示,该检测体系检测灵敏度更高。     

Viruses and viroids of stone fruits in Syria

Field surveys were carried out in the main stone fruit-growing areas of Syria to evaluate the sanitary status of mother blocks, varietal collections and commercial orchards. The presence of virus and virus-like diseases was checked by enzyme-linked immunosorbent assay (ELISA), sap transmission to herbaceous hosts, testing on the woody indicators Prunus persica cv. GF 305 and Prunus serrulata cv. Kwanzan and dot-blot hybridization tests. A total of 1337 samples was tested by ELISA (444 apricot, 283 peach, 246 cherry, 222 almond and 142 plum). The overall mean infection rate was 13%, and the percentage infection level of single species was: peach 24%, cherry 16%, almond 13.5%, apricot 6%, plum 5%. The following viruses and viroids were detected: PNRSV, PDV, ACLSV, PPV, ApMV, PLMVd and HSVd ¹ .     

Genetics of resistance to cotton leaf curl disease in Gossypium hirsutum

Twenty-two cotton varieties were screened for resistance to cotton leaf curl disease (CLCuD), a disease of viral origin, using three procedures: field evaluation, whitefly transmission assay and graft inoculation. Viral infection of cotton varieties was determined by visual symptom assessment as well as dot-blot and multiplex PCR diagnostic techniques. Crosses were made between the most susceptible variety (S-12) and highly resistant varieties (CP-15/2, LRA-5166 and CIM-443). All F₁ plants of these crosses were resistant, showing dominant expression of the resistance as well as the absence of extrachromosomal inheritance. The F₂ plants of the crosses CP-15/2 × S12, LRA-5166 × S-12 and CIM-443 × S12 exhibited a ratio of 13 resistant (symptomless) to three susceptible (with symptoms). Screening of the F₂ generation for virus infection by multiplex PCR further subdivided the resistant class into those exhibiting a high level of resistance (HR; PCR-negative) and those exhibiting resistance (R; symptomless, yet showing virus replication by PCR analysis). Hence, the final ratio was 3:10:3 (HR:resistant:susceptible). The F₃ progeny of susceptible F₂ plants segregated for resistance, indicating the probable presence of a suppressor gene ( S ). These findings are consistent with three genes being involved in G. hirsutum resistance to CLCuD, two for resistance ( R _1CLCuDhir and R _2CLCuDhir ) and a suppressor of resistance ( S _CLCuDhir ).     

THE INTERRELATIONSHIP BETWEEN TILLERS AND RHIZOMES OF POA PRATENSIS L.—AN AUTORADIOGRAPHIC STUDY

Summary. The main shoot or selected tillers of seedling plants of Poa pratensis L. were supplied with ¹⁴CO₂ and the distribution of ¹⁴C-assimilates was followed by autoradiography. The primary tillers were initially supplied with ¹⁴C-assimilates from the main shoot but, once established, became independent of the parental shoot for carbohydrates. Similarly, developing rhizome-tillers were supported by the main shoot and established primary tillers but soon became self-supporting, Defoliation of all the tillers of the plant but one led to the defoliated primary and rhizome tillers being supplied with radiocarbon from the remaining intact shoot. Thus, although the primary tillers and rhizome-tillers in the intact plant appear to be physiologically independent, the entire tiller-rhizome system may be re-integrated after defoliation, allowing assimilate redistribution. P. pratensis may be regarded as a convenient link between the non-weedy herbage grasses which generally lack rhizomes and the weedy rhizomatous grasses typified by Agropyron repens (L.) Beauv.
Etat des relations entre les talles et les rhizomes de Poa pratensis L. Etude autoradiographique     

Parietaria mottle virus, a possible new ilarvirus from Parietaria officinalis (Urticaceae)

A previously undescribed virus, probably a new member of the ilarvirus group, was isolated from Parietaria officinalis showing symptoms of yellow mosaic or mottling. This virus, for which the name parietaria mottle virus (ParMV) is proposed, differs in host range from other ilarviruses. ParMV was purified from Chenopodium quinoa by sap clarification with chloroform, and differential and sucrose density gradient centrifugation.
Purified particles were quasi-isometric to ovoid with diameters of about 24, 29 and 36 nm; no bacilliform particles were detected. Buoyant density in caesium chloride, determined on glutaraldehyde-fixed virus, was 1.35 g/cm³.
An antiserum to ParMV was obtained with a titre of 1:32 in agar gel double-diffusion tests. ParMV did not react with eight other viruses or virus strains belonging to the ilarvirus group or to pelargonium zonate spot virus.
Polyacrylamide gel electrophoresis indicated that ParMV contains a single major protein species of estimated molecular weight 24300 Da and four RNA species of estimated molecular weight 1 37, 1.19, 0.86 and 0.36 × 10⁶ Da.     

Uptake and translocation of imazethapyr in peas as affected by parasitism of Orobanche crenata and herbicide application methods

[¹⁴C]-Imazethapyr was applied as a seed treatment and at plant pre-emergence and post-emergence to peas ( Pisum sativum L.) parasitized by Orobanche crenata Forsk. Herbicide uptake increased with time regardless of the application method. Uptake reached about 98%, 89%, 81% and 94% of the total herbicide applied for the seed coating, seed soaking, pre-emergence and post-emergence treatments respectively. Herbicide translocation within the host plants consistently differed between O. crenata -infected and non-infected plants. High levels of ¹⁴C activity were accumulated by parasitic plants from the host. In non-infected pea plants, pods were stronger sinks for imazethapyr than the other parts of the plant, regardless of the application method. The herbicide distribution in the pea plant: O. crenata complex showed the same pattern regardless of the application methods. However, accumulation of radioactivity in the parasite was lower with pre-emergence and post-emergence application than with the seed treatments. In addition, radioactivity concentration in O. crenata plants was slightly higher when [¹⁴C]-imazethapyr was applied to pea seeds by coating than by soaking.     

TRANSLOCATION OF AMINOTRIAZOLE AND DALAPON IN AG ROPY RON REPENS (L.) BEAUV.

Summary. Tracer studies using single drops of solutions containing 3–amino-1,2,4–triazole-5–¹⁴C (aminotriazole-¹⁴C) or 2,2–dichloropropionic acid-2–¹⁴C (datapon-¹⁴C) revealed that in couch plants (Agropyron repens (L.) Beauv.) growing under field conditions in the autumn and at the stage where the aerial shoots were 40–50 cm long, both compounds moved in both symplast and apoplast. Dalapon was less mobile in the symplast than aminotriazole and only negligible amounts of dalapon were translocated to the rhizomes. The nodes of the treated shoots appeared to act as barriers to translocation, a phenomenon more pronounced for dalapon than for aminotriazole.
Application to a basal green leaf led to a more uniform distribution of the compounds within plants and rhizomes than when the application was made to the youngest fully-expanded leaf.
In couch plants with aerial shoots 10–15 cm long treated in the stubble, the distribution of both aminotriazole and dalapon was mainly restricted to the treated shoots. Even 15 days after application only trace amounts of radioactivity could be found in the rhizomes and untreated shoots.