Experimental infection of the squirrel (Sciurus vulgaris) and the muskrat (Ondatra zibethica) with Tahyna virus (California group, Bunyaviridae)

Two squirrels aged 16 weeks and three muskrats aged 24 weeks were subcutaneously infected with a dose of 400 SMicLD50 of the extraneurally passaged "236" strain of Tahyna virus. Viremia was detected in one squirrel (48 and 96 hours post infection) and in two muskrats (24 and 48 hours p.i.). Seroconversion was demonstrated by plaque-reduction neutralization test (PRNT) 21 days p.i. in all animals.     

Redescription of Andrya cuniculi (Blanchard, 1891) (Cestoda: Anoplocephalidae), a parasite of Oryctolagus cuniculus (Lagomorpha) in Spain

Andrya cuniculi (Blanchard, 1891) (Cestoda: Anoplocephalidae) is redescribed from Oryctolagus cuniculus (L.) from Spain. Large ranges of variability in body length and width, testes number and position of the cirrus sac were observed. An external seminal vesicle covered with small glandular cells is present. The pattern of development of the uterus is similar to that of Andrya rhopalocephala (Riehm, 1881). The only reliable differential characters to distinguish A. cunliculi from A. rhopalocephala are the position of the uterus in gravid segments and the position of the testes in mature segments. The uterus of A. cuniculi occupies the median field and parts of the lateral fields but is restricted to the median field in A. rhopalocephala. Testes are distributed more symmetrically lateral to the female organs in A. cuniculi but are mostly antiporal in A. rhopalocephala.     

Experimental transmission of the mild strain of Tomato yellow leaf curl virus (TYLCV) to Amaranthus dubius by Bemisia tabaci

Tomato yellow leaf curl virus (TYLCV) is a monopartite begomovirus from the Old World. The mild strain of this virus (TYLCV-Mld) was described for South America in Venezuela in 2007. Due to the potential risks of establishment of this virus in the field, six common weeds were evaluated for susceptibility to an isolate of TYLCV-Mld by using adults of Bemisia tabaci (Hemiptera: Aleyrodidae) to mediate viral transmission. In this work, detection based on PCR amplification with TYLCV specific primers showed Amaranthus dubius (Amaranthaceae) as the only infected weed. In A. dubius, viral symptoms were observed from 11.0?±?1.3?days post-inoculation and the transmission rate of TYLCV-Mld to this plant species was 83.3%. The successful back-transmission of TYLCV-Mld from A. dubius to tomato plants was demonstrated.     

Experimental transmission of Caryospora kutzeri (Apicomplexa: Eimeriidae) by rodent hosts

Four laboratory-hatched European kestrels Falco tinnunculus L. were fed on laboratory mice and common voles Microtus arvalis Pallas previously inoculated with different doses of sporulated oocysts of Caryospora kutzeri B?er, 1982. Two kestrels that were fed infected mice shed C. kurtzeri oocysts 6 days after ingesting murine tissues. To compare direct and indirect transmissions, two of the kestrels were subsequently directly inoculated with 10(5) sporulated C. kutzeri oocysts and became patent on days 8 and 9 and shed caryosporan oocysts up to day 25 post inoculation. Additionally, four mice were inoculated with 10(6) oocysts in order to examine mouse tissues for the presence of developmental stages of C. kutzeri. No coccidian stages were found in the tissues of inoculated mice. The experiment showed that developmental stages of C. kutzeri are able to survive in mouse tissues and cause infection of suitable host after their ingestion.     

Experimental infection of pheasants with Lednice (Yaba 1) virus.

Young pheasants (24-hour- and 7-day-old) are capable of producing viraemia and antibodies after experimental infection with Lednice virus even after low doses of virus (0.7-0.9 log mouse LD50/g). Viraemia lasts approximately 3 days, but the titres of virus in the blood are low. The possible role of young pheasants in the circulation of virus in nature is discussed.     

西花蓟马传播番茄斑萎病毒研究进展

西花蓟马Frankliniella occidentalis是世界性重要检疫性害虫之一,不仅直接取食危害作物而且传播病毒,从而造成极为严重的经济损失。由于西花蓟马在我国具有广泛的适生范围,随其入侵我国并随之传播的番茄斑萎病毒(Tomato spotted wilt virus)已在我国不同地域发现,对经济作物已形成严重威胁。本文综述了西花蓟马对番茄斑萎病毒的获取、携带和传播扩散过程及其病毒在蓟马体内的循环过程和机理,总结了影响西花蓟马传播番茄斑萎病毒效率的因素,并评述了西花蓟马-病毒-植物这一互作系统及其对西花蓟马生长发育适合度的影响,以期为我国西花蓟马传播番茄斑萎病毒的基础研究和防控提供理论依据与指导。     

Susceptibility of wild carrot (Daucus carota ssp. carota) to Sclerotinia sclerotiorum

Sclerotinia soft rot, caused by Sclerotinia sclerotiorum, is a severe disease of cultivated carrots (Daucus carota ssp. sativus) in storage. It is not known whether Sclerotinia soft rot also affects wild carrots (D. carota ssp. carota), which hybridise and exchange genes, among them resistance genes, with the cultivated carrot. We investigated the susceptibility of wild carrots to S. sclerotiorum isolates from cultivated carrot under controlled and outdoor conditions. Inoculated roots from both wild and cultivated plants produced sclerotia and soft rot in a growth chamber test. Two isolates differed significantly in the ability to produce lesions and sclerotia on roots of both wild carrots and cv. Bolero. Flowering stems of wild carrots produced dry, pale lesions after inoculation with the pathogen, and above-ground plant weight was significantly reduced 4 weeks after inoculation in a greenhouse test. Wild and cultivar rosette plants died earlier and fewer plants survived when inoculated with the pathogen under outdoor test conditions. Cultivar plants died earlier than wild plants, but survived as frequently. Plants inoculated in the crown died earlier and at a lower frequency than plants inoculated on leaves. Wild carrots may thus serve as a host of S. sclerotiorum and thus eventually benefit from any uptake of resistance genes, among them transgenes, via introgression from cultivated carrots.     

Chloroplastic resistance to triazine herbicides in Sinapis arvensis L. (wild mustard)

Leaf chlorophyll fluorescence (LCF) of atrazine-susceptible Sinapis arvensis L. (wild mustard) biotype was greatly increased (119–181%)and the Hill reaction activity of isolated chloroplasts was inhibited by 10⁴ M of either atrazine, metribuzin or diuron. In contrast the LCF as well as photochemical activity of the chloroplasts of resistant biotype remained unaffected by 10⁴ M atrazine. However, in response to 10⁴ M metribuzin, LCF of the resistant biotype increased by 43% and Hill reaction activity of the chloroplasts was partially blocked. Complete inhibition of the Hill reaction and a 96% LCF increase in response to diuron indicated that the atrazine-resistant S. arvensis biotype had no tolerance to diuron. Similar chloroplast photoreaction responses were observed when the known atrazine-susceptible and resistant Brassica campestris L. (bird's rape) biotypes and B. napus L. cv. Laurentian (rutabaga) genotypes were subjected to the triazine and urea herbicides. These results indicate that resistance to atrazine, in the resistant S. arvensis biotype, is based in the chloroplasts and could involve a selective modification of the PS II complex with respect to the triazine herbicides. Résistance chloroplastique aux herbicides de la famille des triazines chez Sinapsis arvensis L. (moutarde des champs) Chez un biotype de Sinapis arvensis L. (Moutarde des champs) sensible à l'atrazinc. la fluorescence chlorphyllienne des feuilles était fortement augmentée (de 119 à 181%), et la réaction de Hill des chioroplastes isolés, fortement diminuée, par des traitements à l'atrazinc. la métribuzine ou le diuron 10⁴ M. Par contre, ni la fluorescence chlorophyllienne ni la réaction de Hill n'étaient affectées par de l'atrazine 10⁴ M chez un biotype résistant. Toutefois, en réponse à de la métribuzine 10⁴ M, la fluorescence chlorophyllienne du biotype résistant était augmentée de 43%, et la réaction de Hill chez les chioroplastes était partiellement bloquée. L'inhibition complète de la réaction de Hill et une augmentation de 96% de la fluorescence chlorophyllienne après traitement au diuron indiquaient que le biotype de S. arvensis résistant à l'atrazine ne manifestait pas de tolérance à l'égard du diuron. Par comparaison, des réponses chloroplasliques similaires ont été obtenues lorsque des biotypes de Brassica campestris L. (navette des oiseaux) et des génotypes de B. napus L. cv Laurentian (rutabaga) sensibles ou résistants à l'atrazinc ont été traités par des herbicides de la famille des triazines et des urées substituées. Ces résultats montrent que la résistance à l'atrazine, chez le biotype S. arvensisétudié, est un caractère chloroplastique et implique probablement une modification sélective du complexe PS II à l'égard des triazines. Chlaraplastenresistenz gegen Triazinherbizide bei Sinapis arvensis L. (Ackersenf) Bei atrazinempfindlichen Biotypen von Sinapis arvensis L. wurde die Blattchlorophyll-Fluores-zenz (LCF) in isolierten Chloroplasten durch 10⁴m Atrazin, Metribuzin oder Diuron stark gesteigert (119–181%), die Hillreaktion aber gehemmt. In resistenten Biotypen hingegen blieben LCF und die photochemische Aktivität durch 10^?4m Atrazin unbeeinflusst. Resistente Biotypen reagierten auf 10^?4m Metribuzin mit einer Erhöhung der LCF um 43% während die Hillreaktion in den Chloroplasten teilweise blockiert wurde. Eine komplette Hemmung der Hillreaktion und eine um 96% gesteigerte LCF durch Diuron weisen darauf hin, dass atrazinresistente Biotypen von S. arvensis gegenüber Diuron nicht resestent sind. Aehnliche Veränderungen der Photoreaktionen in Chloroplasten konnten beobachtet werden, wenn atrazinemp-findliche und -resistente Brassica campestris L., Biotypen (Ackerkohl) und B. napus L. cv. Laurentian, Genotypen (Kohlrübe) Triazin- und Harnstoffherbiziden exponiert wurden. Diese Ergebnisse weisen darauf hin, dass die Ursache der Unempfindlichkeit gegenüber Atrazin bei den resistenten S. arvensis-Biotypen in den Chloroplasten liegt und dass eine selektive Veränderung des PS II Komplexes in Bezug auf die Triazinherbizide eingeleitet werden kann.     

Seed transmission of Sweet potato leaf curl virus in sweet potato (Ipomoea batatas)

Sweet potato leaf curl virus (SPLCV) infects sweet potato and is a member of the family Geminiviridae (genus Begomovirus). SPLCV transmission occurs from plant to plant mostly via vegetative propagation as well as by the insect vector Bemisia tabaci. When sweet potato seeds were planted and cultivated in a whitefly‐free greenhouse, some sweet potato plants started to show SPLCV‐specific symptoms. SPLCV was detected by PCR from all leaves and floral tissues that showed leaf curl disease symptoms. More than 70% of the seeds harvested from SPLCV‐infected sweet potato plants tested positive for SPLCV. SPLCV was also identified from dissected endosperm and embryos. The transmission level of SPLCV from seeds to seedlings was up to 15%. Southern blot hybridization showed SPLCV‐specific single‐ and double‐stranded DNAs in seedlings germinated from SPLCV‐infected seeds. Taken altogether, the results show that SPLCV in plants of the tested sweet potato cultivars can be transmitted via seeds and SPLCV DNA can replicate in developing seedlings. This is the first seed transmission report of SPLCV in sweet potato plants and also, to the authors' knowledge, the first report of seed transmission for any geminivirus.     

The effects of co‐infection by different Potato virus Y (PVY) isolates on virus concentration in solanaceous hosts and efficiency of transmission

The influence of co‐infection on concentration and accumulation of genetically different isolates of Potato virus Y (PVY) in potato and tobacco plants and the efficiency of transmission by Myzus persicae of PVY isolates from doubly versus singly infected plants were evaluated. The vector ability to simultaneously transmit two virus isolates was examined. Eight PVY isolates represented three strain groups: PVY^O (pathotype and serotype O), PVY^NW (pathotype N and serotype O), and PVY^NTN (pathotype and serotype N). Different diagnostic methods, including DAS‐ELISA, multiplex RT‐PCR, aphid transmission tests and bioassays, were applied to detect the presence of PVY isolates in source and assay plants. Significant reductions in concentrations of certain PVY isolates during co‐infection with other isolates were found both in potato and tobacco plants. The observed effects were both isolate‐ and host‐dependent in form. The highest rates of virus transmission by single aphids were recorded with PVY^NTN isolates, and the lowest ones with PVY^O isolates. Individual aphids of M. persicae were able to simultaneously transmit two PVY isolates. The frequency of transmission was generally low, but it reached as high as 20% for one of the isolate combinations. The findings presented in the work provide proof for antagonistic within‐plant interactions between isolates of PVY, with some implications of these interactions for virus transmission by aphid vectors. Consequently, this research contributes to a better understanding of the epidemiology of the disease caused by PVY.     

Identification and transmission of Piper yellow mottle virus and Cucumber mosaic virus infecting black pepper (Piper nigrum) in Sri Lanka

Sri Lankan black pepper with symptoms of yellow mottle disease contained a mixture of viruses: Piper yellow mottle virus (PYMV) particles (30 × 130 nm), Cucumber mosaic virus (CMV, 30 nm diameter isometric particles), and unidentified, isometric virus-like particles (30 nm diameter). An effective purification procedure is described for PYMV. Immunosorbent and conventional electron microscopy successfully detected badnavirus particles only when at least partially purified extracts were used. PYMV was confirmed as the cause of the disease, with the other two viruses apparently playing no part in producing symptoms. PYMV was transmitted by grafting, by the insect vectors citrus mealy bug ( Planococcus citri ) and black pepper lace bug ( Diconocoris distanti ), but not by mechanical inoculation or through seeds. The CMV isolate was transmitted to indicator plants by mechanical inoculation and by the vector Aphis gossypii , but not by Myzus persicae ; but neither mechanical nor insect transmission of CMV to black pepper was successful. A sensitive polymerase chain reaction assay was developed to detect PYMV in black pepper.     

植物源病毒抑制剂VFB对烟草抗烟草花叶病毒的诱导作用研究

为揭示植物源病毒抑制剂VFB的抗病毒机理,本研究以普通烟和烟草花叶病毒(TMV)为材料,测定了VFB进行预防和治疗处理后烟草中与抗病性相关的部分生理生化指标变化。结果表明:VFB可明显抑制病毒侵染后导致的细胞膜通透性增大;SOD、CAT、β-1,3-葡聚糖酶和几丁质酶等细胞防御酶活性增强,且预防处理的效果优于治疗处理;与抗病性呈正相关的脯氨酸和总游离氨基酸的含量有显著的提高。表明VFB可诱导植物产生抗病性,增强烟草对TMV侵染的抵抗能力。