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1.
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: PVYO (pathotype and serotype O), PVYNW (pathotype N and serotype O), and PVYNTN (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 PVYNTN isolates, and the lowest ones with PVYO 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.  相似文献   

2.
Two Potato virus Y (PVY) isolates collected in Brazil, PVY‐AGA and PVY‐MON, were identified as recombinants between two parent genomes, PVYNTN and PVY‐NE‐11, with a novel type of genomic pattern. The new recombinants had an ordinary PVYNTN genome structure for approximately 6·7‐kb from the 5′‐end of the genome whereas the 3′‐terminal 3·0‐kb segment had two fragments of NE‐11‐like sequence separated by another small PVYNTN‐like fragment. PVY strains are defined based on the hypersensitive resistance (HR) response in potato indicators. Both PVY‐AGA and PVY‐MON isolates did not induce the HR in potato cultivars carrying Ny, Nc, or (putative) Nz genes and thus were able to overcome all known resistance genes to PVY. Only one of the two isolates, PVY‐AGA, induced a vein necrosis reaction in tobacco. The biological responses of the potato indicators and tobacco defined PVY‐MON as an isolate of the PVYE strain. To distinguish PVY‐AGA and PVY‐MON from other PVYNTN isolates, an RT‐PCR test was developed utilizing new specific primers from the capsid protein gene area and producing a characteristic 955‐bp band. Serological profiling of these PVY isolates with three monoclonal antibodies revealed an unusual reactivity, where one of the two commercial PVYN‐specific monoclonal antibodies did not recognize PVY‐AGA. The ability of these new PVY recombinants to overcome resistance genes in potato producing mild or no symptoms, combined with the lack of serological reactivity towards at least one PVYN‐specific antibody may present a significant threat posed by these isolates to seed potato production areas.  相似文献   

3.
In 2008 and 2009 seasons, a sudden increase in Potato virus Y (PVY) incidence was recorded in foundation seed potatoes in Hokkaido, northern Japan. This increase was obvious during the field inspection and the postharvest indexing. Molecular typing revealed that besides the previously reported strains of PVYO and PVYNA‐N, the most common strain identified was the recombinant PVYNTN, with three characteristic recombinant junctions at the HC‐Pro, VPg and CP regions. No potato tuber necrotic ringspot disease (PTNRD) was observed in foundation seed potatoes in correlation with the presence of PVYNTN. Moreover, an isolate with a typical PVYNTN recombinant genome, namely Eu‐12Jp, did not induce PTNRD in 62 Japanese potato cultivars tested in both primarily and secondarily infected plants. Two cultivars carrying the extreme resistance gene Rychc were resistant to the infection with Eu‐12Jp, which presents potential sources of resistance to PVYNTN. Eu‐12Jp induced systemic mottle in potato cultivars Desiree and King Edward carrying resistance genes Ny and Nc, respectively, but induced a hypersensitive reaction in potato cultivar Maris Bard, with the Nz hypothetical resistance gene typical of the PVYZ strain group. Therefore, based on the genome structure and the reaction of the potato N resistance genes, Eu‐12Jp should be classified as PVYZ‐NTN, as described for isolates from Idaho, USA recently. This is the first report of PVYZ‐NTN in Japan and the sudden and increased occurrence of PVYNTN/PVYZ‐NTN represents a potential risk of PTNRD developing and increases the significance of PVY in Japan.  相似文献   

4.
Differences in the early responses of two potato cultivars, Igor and Nadine, to two isolates of Potato virus Y (PVY), the aggressive PVYNTN and the mild PVYN, were monitored. Microarray and quantitative real‐time PCR analyses were carried out to identify differentially expressed genes after inoculation with each virus isolate. Additionally, symptom severity and development was observed and the amount of virus isolate accumulated in systemically infected leaves was evaluated, where a significantly higher amount of PVYNTN was detected. Microarray analysis revealed 572, 1288 and 1706 differentially expressed genes at 0·5, 12 and 48 h post‐inoculation, respectively in cv. Igor, with a similar pattern observed in cv. Nadine. Microarray and quantitative real‐time PCR results implied an earlier accumulation of sugars and lower photosynthesis in leaves inoculated with the aggressive isolate than in leaves inoculated with the mild isolate. The PVYNTN isolate did not activate early differential expression of the Fe‐superoxide dismutase and pectin methylesterase inhibitor (PMEI) genes, indicating a delay in plant response relative to that following PVYN inoculation. Differences in the expression of the β‐glucanase‐I gene were also observed in early plant responses to inoculation with each virus isolate.  相似文献   

5.
The effect of cultivation temperatures on the resistance reaction to three Potato virus Y strains (PVYO, PVYN and PVYNTN) in potato cultivars carrying Rychc was examined. When potato plants carrying Rychc were cultivated at 22 °C, a few small necrotic spots developed on inoculated leaves by 5 days after mechanical inoculation (dpi), and systemic infection of a few symptomless plants was confirmed at 28 dpi by IC‐RT‐PCR. At 28 °C, distinct necrotic spots developed on inoculated leaves by 5 dpi, and systemic symptoms occasionally appeared at 28 dpi. Thus, high temperature weakens Rychc‐conferred resistance. However, the incidence of systemic infection and the titre of virus in resistant cultivars at 28 °C were lower than in a susceptible cultivar. In graft inoculation under high summer temperatures, some plants developed necrosis on the leaves and stem, but PVY was barely detected by RT‐PCR in leaves on potato carrying Rychc. When seedlings from progeny tubers of plants that were inoculated with PVY and grown in a greenhouse at >30 °C in the daytime were examined by ELISA and IC‐RT‐PCR, PVY was not detected in cultivars carrying Rychc. These results show that Rychc confers an extreme resistance to PVY strains occurring in Japan.  相似文献   

6.
Surveys were conducted of symptomatic potato plants in late season crops, from the major potato production regions in Northern Tunisia, for infection with six common potato viruses. The presence of Potato leafroll virus (PLRV), Potato virus Y (PVY), Potato virus X (PVX), Potato virus A (PVA), Potato virus S (PVS) and Potato virus M (PVM) was confirmed serologically with virus infection levels up to 5.4, 90.2, 4.3, 3.8, 7.1 and 4.8%, respectively. As PVY was prevalent in all seven surveyed regions, further biological, serological and molecular typing of 32 PVY isolates was undertaken. Only one isolate was shown to induce PVYO-type symptoms following transmission to tobacco and to react only against anti-PVYO-C antibodies. Typical vein necrosis symptoms were obtained from 31 samples, six of which reacted against both anti-PVYN and anti-PVYO-C antibodies showing they contained mixed isolates, while 25 of them reacted only with anti-PVYN antibodies. An immunocapture RT-PCR molecular test using a PVYNTN specific primer pair set in the 5’NTR/P1 genomic region and examination of recombinant points in three genomic regions (HC-Pro/P3, CI/NIa and CP/3’NTR) showed that all 25 serotype-N PVY isolates were PVYNTN variants with similar recombinations to the standard PVYNTN-H isolate. This is the first report of the occurrence of the PVYNTN variant and its high incidence in late season potatoes in Tunisia.  相似文献   

7.
Biological and whole genome properties were compared between eight historical European (1943–1984) and five Australian (2003–2012) Potato virus Y (PVY) isolates. Based on eliciting hypersensitivity genes Nc, Ny or Nz, the former belonged to biological strain groups PVYC (CT, CRM1), PVYO (CRN, KE, RS) or PVYZ (CM2, CRM2, DS). The latter were inoculated to differential and other potato cultivars, tobacco and tomato. Two belonged to PVYO (BL, DEL3), one to PVYZ (ATL1), and one (KIP1) to suggested strain group (PVYD) which elicited putative hypersensitivity gene Nd. Tomato isolate CN1 (and unsequenced CN2), which were poorly adapted to infect potato, were not grouped. Next‐generation sequencing (NGS) of samples containing all isolates except CN2, yielded 13 complete sequences of 9592–9700 nucleotides (nt), and one partial sequence of 9002 nt, none being recombinants. Comparing the former with 60 other PVY complete genomes, found one (CRM2) in phylogenetic subgroup YO, eight in YO5 (CM2, CRN, DS, KE, RS, ATL1, BL, DEL3), three in YC2 (CRM1, CT, KIP1) and one in YC1 (CN1). Thus, biologically defined PVYO (5) and PVYZ (4) isolates were within phylogenetic subgroups YO or YO5, biological PVYC isolates (2) within YC2, biological PVYD isolate KIP1 in YC2 and tomato isolate CN1 in YC1. NGS identified KIP1 and partial sequence KIP from mixed infection. KIP was in YO5. Grouping of four PVYZ isolates within phylogenetic PVYO, and the PVYD isolate within phylogenetic PVYC, reveals disagreement between current biological and phylogenetic PVY nomenclature systems. Using Latinized numerals for phylogenetic group names resolved this.  相似文献   

8.
In the context of an epidemiological study on Potato virus Y (PVY) in potato crops, Solanum elaeagnifolium Cav. was included in the weeds prospected. Surveys were carried out in four seed potato areas: Cap Bon, Manouba, Jendouba and Kairouan. S. elaeagnifolium was found in all areas, except Cap Bon. Virus‐like symptoms were observed on some S. elaeagnifolium plants in the field, i.e. leaf mottling and curling. Aphids were collected on these plants and were identified as Myzus persicae and Aphis fabae, both known to colonize potatoes and to transmit the standard PVYN isolate with transmission efficiencies of 95% and 43%, respectively. Forty‐seven plant samples were tested with ELISA for the presence of PVY. Positive reactions were obtained from 2/6, 5/18, 8/23 samples collected in Manouba, Jendouba and Kairouan, respectively. Virus transmission was carried out using M. persicae as vector from two samples of each region onto plantlets of Nicotiana tabacum cv Xanthi. All inoculated plantlets displayed typical symptoms of the PVYN strain group, confirmed by serological testing using specific antibodies. This is the first report of a PVY natural infection on S. elaeagnifolium in Tunisia. The abundance of this weed, its over‐wintering status and the high rate of PVY‐infected plants (31.9%) allow us to deduce that S. elaeagnifolium must be considered a reservoir species of PVY under natural conditions in Tunisia and probably in other Mediterranean countries. The presence of efficient aphid vectors of PVY on this weed in crops is additional evidence that S. elaeagnifolium may become a problem by acting as a source plant for PVY spread in potato crops.  相似文献   

9.
Two important sources of Capsicum annuum (bell pepper) resistance were evaluated for their response to inoculation with two isolates of Tobacco etch virus strain NW (TEV‐NW, genus Potyvirus). The resistant cultivars were CA4 and Dempsey, which contain the pvr1 and pvr12 resistance genes, respectively. TEV‐NW was maintained by mechanical passage in the susceptible pepper cultivar Early Calwonder and Nicotiana tabacum cv. Kentucky 14. In initial experiments, the TEV‐NW isolate maintained in Early Calwonder infected two of seven CA4 plants; however, none of the CA4 plants inoculated with the TEV‐NW isolate maintained in Kentucky 14 were infected. The infected CA4 plants had low virus titres in non‐inoculated leaves and did not develop visible symptoms. When the infected CA4 plants were used as inoculum of additional CA4 plants, all newly inoculated plants became infected, developed systemic symptoms and accumulated virus in non‐inoculated leaves more quickly than the originally infected CA4 plants. This new NW isolate, referred to as NW‐CA4, was shown to overcome the resistances expressed by both CA4 (pvr1) and Dempsey (pvr12). The potyviral VPg is believed to be the determinant for pvr1 and pvr12 resistance genes, both of which are eIF4E‐encoding genes. The VPg amino acid sequence for NW‐CA4 was determined and compared with that of NW isolates and different TEV strains. No amino acid variation was identified that explained the infectivity of NW‐CA4 in CA4 and Dempsey plants.  相似文献   

10.
Y. You  Y. Shirako 《Plant pathology》2013,62(1):226-232
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11.
In UK, the tobacco veinal necrosis strain of potato virus Y (PVYN), potato virus A (PVA) and potato virus V (PVV) each occur in the field only in limited ranges of potato cultivars in which they mostly cause mild symptoms or even symptomless infection; little is known about incidence of strain C of PVY (PVYC). The ordinary strain of PVY (PVY°), however, is widespread causing symptoms ranging in severity from very severe through to very mild, depending on cultivar sensitivity/tolerance. During field inspections, very mild potyvirus symptoms may be missed, so inspectors are trained to be particularly vigilant when examining problem cultivars which react in this way. PVA is almost invariably treated, along with PVX, as a mild kind of virus infection, but infections with PVY°, PVYN and PVV are treated as severe with stricter tolerances being applied for them (especially for PVYN) regardless of symptom severity. Wide variation within the same cultivar in the behaviour of variants within the PVY° strain group also sometimes causes difficulties in interpretation at inspection. To detect PVY, PVA and PVV in routine serological testing on potato certification samples, it is necessary to employ specific antisera to each of them. PVYN-specific monoclonal antibodies can be used in ELISA to distinguish PVYN from PVY°.  相似文献   

12.
A potyvirus known to be an important agent involved in causing a disease of trailing petunias, was identified as being a member of the necrotic strain of potato virus Y (PVY) using a number of monoclonal antibodies. The sequence of the coat protein gene for the PVY isolate was determined and when compared with sequences for other PVY strains it was shown to cluster closely with isolates of PVYNTN and to have a recombination point present within the coat protein common with other isolates of PVYNTN. When inoculated onto potato tuber necrotic ringspot disease (PTNRD) susceptible potato cultivars the petunia isolate was found to be capable of causing necrotic tuber symptoms, consistent with those caused by other isolates of PVYNTN. Due to the number of similarities it is thought the petunia isolate belongs to the PVYNTN group of isolates. Out of 24 species of bedding and pot plant crops tested, 19 were shown by mechanical inoculation to be susceptible to PVY, highlighting not only a clear risk to a number of commercially important plant species from PVYNTN infected trailing petunias, but also other susceptible crops grown in these areas.  相似文献   

13.
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14.
Verticillium albo‐atrum is responsible for considerable yield losses in many economically important crops, among them alfalfa (Medicago sativa). Using Medicago truncatula as a model for studying resistance and susceptibility to V. albo‐atrum, previous work has identified genetic variability and major resistance quantitative trait loci (QTLs) to Verticillium. In order to study the genetic control of resistance to a non‐legume isolate of this pathogen, a population of recombinant inbred lines (RILs) from a cross between resistant line F83005.5 and susceptible line A17 was inoculated with a potato isolate of V. albo‐atrum, LPP0323. High genetic variability and transgressive segregation for resistance to LPP0323 were observed among RILs. Heritabilites were found to be 0·63 for area under the disease progress curve (AUDPC) and 0·93 for maximum symptom score (MSS). A set of four QTLs associated with resistance towards LPP0323 was detected for the parameters MSS and AUDPC. The phenotypic variance explained by each QTL (R2) was moderate, ranging from 4 to 21%. Additive gene effects showed that favourable alleles for resistance all came from the resistant parent. The four QTLs are distinct from those described for an alfalfa V. albo‐atrum isolate, confirming the existence of several resistance mechanisms in this species. None of the QTLs co‐localized with regions involved in resistance against other pathogens in M. truncatula.  相似文献   

15.
Improved tobacco cultivars introgressed with alleles of the recessive resistance va gene have been widely deployed in France to limit agronomical consequences associated with Potato virus Y (PVY) infections. Unfortunately, necrotic symptoms associated with PVY have been reported on these cultivars suggesting that PVY is able to overcome the resistance. A field survey was performed in France in 2007 to (i) estimate the prevalence of PVY in tobacco plants showing symptoms and (ii) characterize PVY isolates present in susceptible and va‐derived tobacco cultivars. A serological typing procedure, applied to 556 leaves collected from different French tobacco growing areas, was performed using polyclonal antisera raised against different viral species including PVY. Viral species were detected in 80·8% of leaves and PVY was present in 83·5% of infected samples. However, statistical analysis confirmed that the probability of a tobacco plant being infected with PVY is reduced in va hosts. Eighty‐six PVY isolates were mechanically inoculated on one susceptible and three va‐derived tobacco cultivars used as indicator hosts to define virulence of these isolates against alleles 0, 1 and 2 of the va gene. Both qualitative and quantitative analyses showed that 55 PVY isolates were able to overcome the three va alleles. Moreover, the monitored biological diversity of PVY isolates was higher in the susceptible tobacco hosts than in the va‐derived ones. This study helps to understand consequences of the deployment of the va gene in tobacco on diversity and virulence of PVY isolates.  相似文献   

16.
The method currently used for testing potato tubers for viruses following harvest involves a growing‐on test. This takes up to 6 weeks to complete, and there is therefore a demand for more rapid test results. The sensitivity and reliability of direct tuber testing by DAS‐ELISA and real‐time RT‐PCR (TaqMan) were compared with the growing‐on test. In addition, the reliability of all three methods for the detection of Potato Y potyvirus (PVY) in tubers was compared over post‐harvest intervals of 6, 10, 14 and 18 weeks. The test material came from plots of tubers (cv. ‘Maris Piper’) containing a primary infection of strains PVYN and PVYO, following aphid transmission from marked infector plants grown during the 2003 season. Sample material was homogenized and divided, to provide comparative test material for detection of PVY by ELISA and real‐time RT‐PCR. Tuber eye‐plugs were then taken and subjected to the growing‐on test. The remainder of the tuber was also grown on and tested, to ensure infection was not missed as a consequence of an uneven distribution of virus throughout the tuber material. The results obtained using the two methods for direct testing of the tubers, and those results obtained from the traditional growing‐on test, are compared. The advantages and disadvantages of each method are discussed.  相似文献   

17.
P. Abad  C. Jord 《EPPO Bulletin》2000,30(2):281-287
A disease caused by potato Y potyvirus (PVY) affects tomato plantations with variable severity in Tenerife Island. Affected plants show diverse symptoms such as necrotic lesions or mild to severe mosaic in leaves and whitish spots in green fruits that remain after ripening. Tomato PVY isolates and few potato and capsicum PVY isolates have been characterized on the basis of biological, serological and molecular criteria. All PVY isolates reacted positively to monoclonal antibodies specific for PVYO/C or PVYN strains, and nearly 50% of tomato PVY isolates were recognized by both. Differentiation of PVY strains according to the response of inoculated experimental plants was confusing due to the variability of viral aggressiveness and symptomatology induced. RFLP analysis of the CP gene and 3’untranslated region (UTR) revealed high variability. In addition to mixed infection by different PVY strains, the biological and molecular properties of those tomato PVY isolates that react to both monoclonal antibodies could be explained as the result of RNA recombination between distinct PVY strains which infect the same host plant.  相似文献   

18.
Stem nodes of the potato virus YNTN(PVYNTN) susceptible potato cultivar (Solanum tuberosum cv. “Igor”) were studied to investigate whether alterations in shoot morphology caused by infection with PVYNTNare related to changes in structure and activity of the shoot apical meristem. The PVYNTNcauses severe disease symptoms known as the potato tuber necrotic ringspot disease (PTNRD) in susceptible potato plants grown in the field. Although in stem node culture the symptoms are mildly expressed, in systemically PVYNTN-infected plants the shoot height stem diameter, number of leaves and the total leaf area were lower than in the healthy control plants at day 18 and 35 of culture. Histological analysis of the longitudinal sections of the shoot tip revealed that the infected plants had smaller shoot apical meristems due primarily to a lower cell number in different meristem zones. One of the most affected zones of the apical shoot meristem was the peripheral zone, the region in which leaf primordia are induced. The data is consistent in showing that the infection of potato plants with PVYNTNleads to alterations in the shoot apical meristem structure and mitotic activity. These changes are, in turn, reflected in altered overall morphology of the infected plant.  相似文献   

19.
Potato virus Y (PVY) is responsible for major viral diseases in most potato seed areas. It is transmitted by aphids in a non-persistent manner, and it is spread in potato fields by the winged aphids flying from an infected source plant to a healthy one. Six different PVY strains groups affect potato crops: PVYC, PVYN, PVYO, PVYN:O, PVYNTN, and PVYN-Wi. Nowadays, PVYNTN and PVYN-Wi are the predominant strains in Europe and the USA. After the infection of the leaf and accumulation of the virus, the virus is translocated to the progeny tubers. It is known that PVYN is better translocated than PVYO, but little is known about the translocation of the other PVY strains. The translocation of PVY occurs faster in young plants than in old plants; this mature plant resistance is generally explained by a restriction of the cell-to-cell movement of the virus in the leaves. The mother tuber may play an important role in explaining mature plant resistance. PVY is able to pass from one stem to the other stems of the same plant through the vascular system of the mother tuber, but it is unknown whether this vascular link between stems is permanent during the whole life of the plant. Two greenhouse trials were set up to study the spread of PVY in the vascular system of the potato plant. The PVY-susceptible cultivar Charlotte was used for both trials. It was demonstrated that all stems growing from a PVY-infected tuber will become infected sooner or later, and that PVYN-Wi translocates more efficiently to progeny tubers than PVYNTN. It was also demonstrated that the progressive decay of the mother tuber in the soil reduces the possibility for virus particles to infect healthy stems through the vascular system of the mother tuber. This new element contributes to a better understanding of the mechanism of mature plant resistance.  相似文献   

20.
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