Resistance of Pepper Lines to the Movement of Cucumber Mosaic Virus

The multiplication and the migration of cucumber mosaic virus (CMV) were studied in greenhouse conditions in one susceptible ‘Yolo wonder’ and two resistant ‘Milord’ and ‘Vania’ pepper varieties. DAS-ELISA tests have revealed that the virus is replicated in inoculated leaves of the resistant varieties as high as in the susceptible variety. In the susceptible variety ‘Yolo wonder’, CMV migrated from the leaf lamina to the petiole two days after inoculation and it became systemic three days later regardless the season. In ‘Milord’ the virus migrated from the leaf lamina to the petiole five days after inoculation and it became systemic during the winter 16 days after inoculation. Whereas plants of the same genotype were not infected systemically during the summer. In ‘Vania’, during the two seasons, CMV spread from the blade to the petiole five days after inoculation, but the virus was not detected beyond the inoculated leaf. These results show that ‘Milord’ and ‘Vania’ are resistant to CMV migration. Therefore, the resistance to CMV migration is affected by plant genotype and temperature. The study of effect of pepper plant phenology on infection has revealed that resistance to CMV migration is also affected by the development stage of the plants.     

Age-related Resistance in Bell Pepper to Cucumber mosaic virus

We demonstrated the occurrence of mature plant resistance in Capsicum annuum‘Early Calwonder’ to Cucumber mosaic virus (CMV) under greenhouse conditions. When Early Calwonder plants were sown at 10 day intervals and transplanted to 10‐cm square pots, three distinct plant sizes were identified that were designated small, medium and large. Trials conducted during each season showed that CMV accumulated in inoculated leaves of all plants of each size category. All small plants (with the exception of the winter trial) developed a systemic infection that included accumulation of CMV in uninoculated leaves and severe systemic symptoms. Medium plants had a range of responses that included no systemic infection to detection of CMV in uninoculated leaves with the systemically infected plants being either symptomless or expressing only mild symptoms. None of the large plants contained detectable amounts of CMV in uninoculated leaves or developed symptoms. When plants were challenged by inoculation of leaves positioned at different locations along the stem or different numbers of leaves were inoculated, large plants continued to accumulate CMV in inoculated leaves but no systemic infection was observed. When systemic infection of large plants did occur, e.g. when CMV‐infected pepper was used as a source of inoculum, virus accumulation in uninoculated leaves was relatively low and plants remained symptomless. A time‐course study of CMV accumulation in inoculated leaves revealed no difference between small and large plants. Analyses to examine movement of CMV into the petiole of inoculated leaves and throughout the stem showed a range in the extent of infection. While all large plants contained CMV in inoculated leaves, some had no detectable amounts of virus beyond the leaf blade, whereas others contained virus throughout the length of the stem but with limited accumulation relative to controls.     

黄瓜花叶病毒衣壳蛋白基因转化辣椒研究

The plant expression vector of the coat protein(CP) gene of cucumber mosaic virus (CMV) BS strain was used to transform three kinds of pepper (Capsicum annuum) tissues (cotyledon, stem and root) by agrobacterium-mediated co-cultivation. 53%-68.4% of the total tissues (639) can be induced to be calli, but only cotyledon calli can be further regenerated to form shoots (regenerated efficiency 39.7%). 70%(42/60) of the putative transformed plants were confirmed to have CP gene in their genomes by Southern blot. The mRNAs and the CP were respectively found in 80% of transgenic plants by Northern blot and DAS-ELISA. 24 of the transgenic plants expressing CP gene of BS strain showed three kinds of resistant level (severe symptom, delay of symptomatic development, no symptom) to infection of CMV-BS and of CMV-P. However, there was distinctly higher resistance to inoculation of CMV-BS than that with CMV-P in these transgenic plants.     

Recovery from Cucumber Mosaic Virus Infection for ‘Calwonder’ Bell Pepper Plants Does not Counter Negative Impacts on Plant Growth

Cucumber mosaic virus (CMV) accumulation in leaves and stems of infected bell pepper plants at specific symptom stages was evaluated with an emphasis on the transition from full infection to recovery from Cucumber mosaic disease. Four symptom phases occurred in successive order, designated chlorosis (leaves 6–8), mosaic (leaves 9–11/12), leaf distortion (first series of leaves on secondary and tertiary branches) and recovery (progressive recovery with newly emerging leaves in tertiary and younger branches). In situ detection of CMV in leaf tissues revealed widespread occurrence in leaves expressing chlorosis and mosaic symptoms but reduced, localized occurrence in leaves in the recovery phase. Similarly, CMV accumulated to high levels throughout stems expressing chlorosis and mosaic symptoms but with dramatically reduced levels for plants in the recovery symptom phase. Stunting of internodes occurred at all locations above the inoculated leaves by the first expression of systemic symptoms, suggesting an impact on stem growth in response to initial virus invasion of young developing tissues of the stem. Despite the recovery from CMV infection, plant growth was negatively impacted early in the infection process and remained so through the course of the experiment.     

辣椒上CMV株系鉴别寄主的筛选与应用

根据“基因对基因”理论和日本小室与都凡按寄主的科属关系及被害症状划分株系的方法,研究了辣椒CMV的“基因型株系”和“致病型株系”。从373个甜、辣椒品种(系)中,筛选出一套抗性不同的差别品种,编号为:LS-8501(HR)、LS-8502(R)、LS-8503(T)、LS-8504(S)、LS-8505(HS)。用这套差别品种做“基因型”株系鉴别寄主,将59个CMV分离物划分为5个株系,命名为:CMV-P0,CMV-P1,CMV-P2,CMV-P3,CMV-P4。又从7科39种不同科属寄主值物中,筛选出一套“致病型”株系的鉴别寄主谱7种,用这套鉴别寄主将59个CMV分离物划分为5个株系群,即十字花科株系群,藜科株系群,茄科、葫芦科株系群,豆科株系群,普通黄色花叶株系群。文中比较了两种方法划分的株系致病性与辣椒病症表现型之间的关系,以及各株系的分布。还讨论了“基因型”鉴别寄主谱及“基因型”株系划分方法盼学术价值和实用性,比较了5个株系与国内外已分化的CMV株系的异同点。     

辣椒抗烟草花叶病毒相关基因研究进展

病毒病是危害辣椒生产的主要病害之一。烟草花叶病毒(TMV)是最早被发现的病毒,它引起的烟草花叶病毒病是多种作物的重要病害,给辣椒等茄科作物的生产带来重大损失。文中综述了辣椒抗TMV防御反应中的相关基因及其研究进展,为明确辣椒抗TMV机理,挖掘抗病基因,选育抗病材料提供参考。     

Response of Resistant and Susceptible Bell Pepper (Capsicum annuum) to a Southern California Meloidogyne incognita Population from a Commercial Bell Pepper Field

To determine the presence and level of root-knot nematode (Meloidogyne spp.) infestation in Southern California bell pepper (Capsicum annuum) fields, soil and root samples were collected in April and May 2012 and analyzed for the presence of root-knot nematodes. The earlier samples were virtually free of root-knot nematodes, but the later samples all contained, sometimes very high numbers, of root-knot nematodes. Nematodes were all identified as M. incognita. A nematode population from one of these fields was multiplied in a greenhouse and used as inoculum for two repeated pot experiments with three susceptible and two resistant bell pepper varieties. Fruit yields of the resistant peppers were not affected by the nematodes, whereas yields of two of the three susceptible pepper cultivars decreased as a result of nematode inoculation. Nematode-induced root galling and nematode multiplication was low but different between the two resistant cultivars. Root galling and nematode reproduction was much higher on the three susceptible cultivars. One of these susceptible cultivars exhibited tolerance, as yields were not affected by the nematodes, but nematode multiplication was high. It is concluded that M. incognita is common in Southern California bell pepper production, and that resistant cultivars may provide a useful tool in a nonchemical management strategy.     

Cucumber Mosaic Virus Movement Protein Severs Actin Filaments to Increase the Plasmodesmal Size Exclusion Limit in Tobacco

Plant viral movement proteins (MPs) enable viruses to pass through cell walls by increasing the size exclusion limit (SEL) of plasmodesmata (PD). Here, we report that the ability of Cucumber mosaic virus (CMV) MP to increase the SEL of the PD could be inhibited by treatment with the actin filament (F-actin)–stabilizing agent phalloidin but not by treatment with the F-actin–destabilizing agent latrunculin A. In vitro studies showed that CMV MP bound globular and F-actin, inhibited actin polymerization, severed F-actin, and participated in plus end capping of F-actin. Analyses of two CMV MP mutants, one with and one without F-actin severing activities, demonstrated that the F-actin severing ability was required to increase the PD SEL. Furthermore, the Tobacco mosaic virus MP also exhibited F-actin severing activity, and its ability to increase the PD SEL was inhibited by treatment with phalloidin. Our data provide evidence to support the hypothesis that F-actin severing is required for MP-induced increase in the SEL of PD. This may have broad implications in the study of the mechanisms of actin dynamics that regulate cell-to-cell transport of viral and endogenous proteins.     

CMV抑制PVYN CP基因沉默及其介导的抗病性

以前曾报道用RNA介导的抗病毒策略,获得了高度抗病的表达马铃薯Y病毒坏死株系外壳蛋白基因(PVY^N CP)的转基因烟草,并对T1、T2代转基因植株进行了遗传和抗病性分析。此次以T,代转基因植株为试验材料,在筛选高度抗病植株并证明其抗病性是基于转基因沉默的基础上,采用Northern杂交的方法,证明CMV侵染抑制了转基因植株中PVY^N CP基因的沉默,而且CMV对PVY^N CP基因沉默的抑制部位是发生在接种后的新生叶上,接种叶及其下部叶片中PVY^N CP基因沉默则未受到影响。采用ELISA方法对CMV PVY^N复合接种的转基因植株进行PVY^N检测,结果表明,接种叶及下部叶没有检测到PVY^N,植株叶片对PVY^N表现为抗病。而在CMV接种后植株新生叶中则检测出了高滴度的PVY^N,植株叶片对PVY^N表现为感病。该文报道了在表达PVY^N CP基因的RNA介导抗性转基因植株中,异源病毒侵染抑制了转基因的沉默,并导致转基因植株的抗病性丧失。     

2个玉米抗矮花叶病分子标记的有效性评价

玉米矮花叶病是玉米重要的病毒病害,培育抗病品种是防治该病最经济有效的方法,将常规育种方法与分子育种技术相结合可以大大提高抗病育种的效率。本研究利用前期研究开发的2个分子标记Indel186-9和SCAR112,检测100份常用玉米自交系的标记基因型,结合100份玉米自交系抗性表型鉴定结果进行2个分子标记辅助选择的有效性分析。结果表明,目前种质资源中高抗病材料较少,亟待进行抗病改良。本试验所用的自交系包括不同血缘,抗源主要来源于PB和四平头种质。Indel186-9标记和SCAR112标记的选择符合率均达到80%,同时使用两者选择符合率达到91.67%,其中抗病选择符合率达到100%。Indel186-9和SCAR112标记分别可以使抗病级别从平均7.26级提高到平均2.4级,平均7.63级提高到平均4.27级。试验证明2个标记均可用于对玉米抗矮花叶病材料的选择,正确组合使用可提高对玉米抗矮花叶病材料的选择效率。     

Soil Solarization and Gliocladium virens Reduce the Incidence of Southern Blight Sclerotium rolfsii in Bell Pepper in the Field

The timing of solarization with clear plastic mulch in relation to the planting of pepper and the timing of soil amendment with a bran prill formulation of Gliocladium virens were evaluated for the control of southern blight and the survival of sclerotia of the pathogen Sclerotium rolfsii in bell pepper in the field. Solarization during crop growth increased the incidence of southern blight, and G. virens was not effective under the mulch. In addition, pepper yields were low when the soil was solarized during crop growth. In contrast, the solarization of fallow soil in raised beds for 6 weeks prior to crop growth significantly reduced disease incidence in the pepper crop. In addition, in 2 years, G. virens alone reduced southern blight in non-solarized soils and reduced the survival of sclerotia of S. rolfsii to depths of 30 cm at all locations in soil in both years. These data demonstrate two effective biological control strategies for the management of southern blight in the southeastern US.     

Field Evaluation of Natural Enemies ofTamarixspp. in Southern France

During 1993, potted plants ofTamarix ramosissimaC. F. Ledebour (saltcedar) from the United States of America andT. gallicaL. from France were placed underTamarix gallicatrees at Sète and Vendémian, southern France, and the natural enemies that attacked these plants were recorded. The most promising natural enemies found were three species ofPsectrosema(Diptera: Cecidomyiidae);Hypophyes pallidulus(Gravenhorst),Corimalia tamarisci(Gyllenhal), andConiatus tamarisciF. (Coleoptera: Curculionidae);Stylosomusprob. tamaricis (Herrich-Schaffer) (Coleoptera: Chrysomelidae); andAgdistis tamaricis(Zeller) (Lepidoptera: Pterophoridae). The host specificity of these insects was studied in a field test during 1994. Of the 11 plant species tested, none of the economically important plants and neitherTamarix aphylla(L.) nor any of the nine genera of plants outside the family Tamaricaceae were attacked. The above mentioned natural enemies seem to be specific feeders on saltcedar and are recommended as prospective agents for biological control ofT. ramosissimain the United States.     

Phloem-Specific Expression of the Tobacco Mosaic Virus Movement Protein Alters Carbon Metabolism and Partitioning in Transgenic Potato Plants

The tobacco mosaic virus movement protein (TMV-MP) has pleiotropic effects when expressed in transgenic tobacco (Nicotiana tabacum) plants. In addition to its ability to increase the plasmodesmal size-exclusion limit, the TMV-MP alters carbohydrate metabolism in source leaves and dry matter partitioning between the various plant organs. In the present study the TMV-MP was expressed under the control of a phloem-specific promoter (rolC), and this system was employed to further explore the potential sites at which the TMV-MP exerts its influence over carbon metabolism and transport in transgenic potato (Solanum tuberosum) plants. Immunohistochemical analyses indicated that the TMV-MP was localized mainly to phloem parenchyma and companion cells. Starch and sucrose accumulated in source leaves of these plants to significantly higher levels compared with control potato lines. In addition, the rate of sucrose efflux from excised petioles was lower compared with control plants. Furthermore, under short-day conditions, carbon partitioning was lower to the roots and higher to tubers in rolC plants compared with controls. These results are discussed in terms of the mode(s) by which the TMV-MP exerts its influence over carbon metabolism and photoassimilate translocation.     

Detection of the 3a Protein of Cucumber Mosaic Virus in a Cell Wall Fraction from Infected Nicotiana clevelandii Plants

The 3a protein of cucumber mosaic virus was expressed in Escherichia coli and, after purification, used to produce an antiserum. The 3a protein was detected in a cell wall fraction obtained from infected Nicotiana clevelandii leaf tissue by immunoblotting using the 3a antiserum. The 3a protein reached a maximum level 4 days after inoculation and remained at this level for a further 8 days before slowly declining. In contrast, the virus capsid protein, detected in an 80 000 g pellet byimmunoblotting using a virus particle antiserum, reached a maximum 5 days after inoculation and remained at this level for at least a further 16 days.     

Induction of Resistance in Tobacco Leaves to Tobacco Mosaic Virus by Dodecylbenzenesulfonate

Application of dodecylbenzenesulfonate (DBS) to half leaves of Nicotiana tabacum cv. Xanthi nc. before TMV inoculation resulted in a marked decrease in lesion number and size as well as in virus content of the lesions in the untreated half leaves. Systemic induction of resistance in untreated leaves of the plants was not detected.     

Detection of the 3a Protein of Cucumber Mosaic Virus in a Cell Wall Fraction from Infected Nicotiana clevelandii Plants

The 3a protein of cucumber mosaic virus was expressed in Escherichia coli and, after purification, used to produce an antiserum. The 3a protein was detected in a cell wall fraction obtained from infected Nicotiana clevelandii leaf tissue by immunoblotting using the 3a antiserum. The 3a protein reached a maximum level 4 days after inoculation and remained at this level for a further 8 days before slowly declining. In contrast, the virus capsid protein, detected in an 80 000 g pellet by immunoblotting using a virus particle antiserum, reached a maximum 5 days after inoculation and remained at this level for at least a further 16 days.     

Influence of Environmental Stress on Biomass Partitioning in Transgenic Tobacco Plants Expressing the Movement Protein of Tobacco Mosaic Virus

The influence of various environmental factors on biomass partitioning between shoots and roots in transgenic tobacco (Nicotiana tabacum) plants expressing the movement protein (MP) of tobacco mosaic virus (TMV) was investigated. TMV-MP-expressing transgenic plants exhibited a root-to-shoot ratio that was approximately 40% below that of transgenic vector control plants. When transgenic plants expressing the TMV-MP were subjected to water-stress conditions, the root-to-shoot ratio was increased to a value comparable to that of control plants subjected to the same water-stress treatment. Although the root-to-shoot ratio was increased by N or P deficiencies, the TMV-MP-induced alteration in biomass partitioning was not overcome. Surprisingly, under K+-deficient growth conditions, both TMV-MP-expressing and control plants exhibited reduced root-to-shoot ratios when compared with plants grown in the presence of sufficient K+. Furthermore, plant growth under K+-deficient conditions did not alleviate the influence of the TMV-MP over resource allocation to the roots. These results are discussed in terms of possible mechanisms by which stress signals could cause an alteration in biomass partitioning between shoots and roots in control and transgenic tobacco plants expressing the TMV-MP.     

Induced Resistance in Hypersensitive Tobacco Against Tobacco Mosaic Virus by Injection of Intercellular Fluid from Tobacco Plants with Systemic Acquired Resistance

Acquired resistance in hypersensitive tobacco plants against tobacco mosaic virus (TMV) was induced by components occurring in the intercellular fluid (IV) obtained from virus-infected plants or by plant cell wall components. Induced resistance could be transmitted through seed to the progeny. Lesion size and number were reduced significantly when the progeny was tested by TMV-inoculation. IV was extracted from the upper uninoculated leaves of four times TMV-inoculated Nicotiana tabacum cv. ‘Xanthi’ nc plants. Injection of IV from induction-inoculated plants (SAR-IV) into leaves of healthy plants followed by TMV-infection reduced lesion size significantly. A concentration of 5 × 10^?7 g SAR-IV/ml was still active. IV from healthy plants was inactive. The IV's were partly purified by gel filtration on a Sephadex G-50 column. Some fractions were active in inducing resistance as expressed in reduction of lesion size. Fractions of control-IV were inactive. It is still unknown whether the active substances in SAR-IV are in fact cell wall fragments acting as regulatory molecules in disease resistance.