Biological and sequence comparisons of Potato virus Y isolates associated with potato tuber necrotic ringspot disease

The biological and molecular relationships between a large number of Potato virus Y (PVY) isolates were examined, concentrating mainly on isolates associated with potato tuber necrotic ringspot disease (PTNRD). Following detailed analysis of the coat-protein gene, four main groups were identified which broadly corresponded to the phenotype of the different isolates. The groups comprised the ordinary strain (PVY^O), the necrotic strain (PVY^N), the C strain (PVY^C) and a group of recombinant (between ordinary and necrotic) isolates. In the latter group, all members were associated with PTNRD. However, four nonrecombinant isolates were also identified which were associated with PTNRD or tuber necrosis. Three were from tubers showing PTNRD symptoms in the field, while the fourth originated from symptomless tubers, but could cause necrotic rings on tubers under glasshouse conditions. The results show that although coat-protein recombination is always found associated with the PTNRD phenotype, some nonrecombinant isolates have very similar biological properties.     

Production of monoclonal antibodies to potato virus YNTN strain and their use for strain differentiation

Four mouse monoclonal antibodies (MAbs) against potato virus Y (PVY) were produced. MAb 4C1 reacted with four isolates of PVY^NTN and only very weakly with one isolate of the necrotic strain of PVY (PVY^N). It did not react with other isolates of the ordinary strain of PVY tested. MAb 2C9 reacted with all isolates tested and can be used to produce a specific diagnostic kit for routine PVY detection. Other MAbs had different specificities and reacted with isolates of various strains of PVY. MAbs did not react with seven other members of the Potyvirus group including potato virus A. A MAb-based ELISA, using MAb 4C1, was devised and shown to detect PVY^NTN specifically.     

PVYNTN-NW, a novel recombinant strain of Potato virus Y predominating in potato fields in Syria

Detailed characterization of a number of isolates of PVY^SYR, a novel recombinant strain of Potato virus Y (PVY) from Syria, was conducted to elucidate their origin, assess their significance and achieve a final classification of PVY^SYR. Recombination analysis grouped isolates of PVY^SYR into three recombination patterns, SYR-I, SYR-II and SYR-III, which varied in the first 700 nucleotides of their genomes, with the second recombination pattern, SYR-II, the most frequent. PVY^SYR isolates shared highest genomic identity and close phylogenetic relationships with PVY^NTN and PVY^NW isolates from Syria, suggesting a common origin and local emergence of these isolates in Syria. All PVY^SYR isolates (total of 20) induced tobacco veinal necrosis, but reacted to a PVY^O monoclonal antibody, typical characteristics of the previously reported PVY^NW (or PVY^N:O). In potato, however, four isolates tested (one of SYR-I and three of SYR-II) induced potato tuber necrotic ringspot disease (PTNRD), which is the characteristic phenotype of PVY^NTN. Given the shared properties of SYR-I and SYR-II isolates with PVY^NTN and PVY^NW, it was decided that they represent a new recombinant strain of the PVY^N strain group, with the proposed name PVY^NTN-NW. The classification of SYR-III will be possible only after testing the phenotype in potato. The high prevalence of PVY^NTN-NW in potatoes and weeds, as well as its ability to induce PTNRD, demonstrates its importance and the necessity for its control.     

Production of monoclonal antibodies against synthetic peptides of the N-terminal region of Potato virus Y coat protein and their use in PVY strain differentiation

Antibodies were prepared against two synthetic peptides, P19 and P11, derived from the coat protein N-terminal region of two pepper isolates of Potato virus Y from Tunisia (PVY-P21 and PVY-P2, respectively). The peptides were selected by comparing the predicted amino acid sequences of three pepper and four potato PVY isolates on the basis of their polymorphism and hydrophilicity. Sera with high titres were only obtained against P19. Three MAbs, raised in response to P19, reacted with the homologous virus (PVY-P21) in TAS-ELISA. When tested against a broad range of PVY isolates and related viruses, MAb 3C5 proved to be PVY species specific, whereas MAbs 8A4 and 1D6 reacted specifically with standard isolates of PVY^O, PVY^C and PVY^N-W strains, but not with other PVY isolates. Consequently, epitope(s) recognized by 8A4 and 1D6 MAbs may be specific to a PVY group comprising all serologically PVY^non–N isolates. Surprisingly, and unlike isolate PVY-P21, many Tunisian field pepper isolates did not carry this epitope(s), thus revealing serological heterogeneity within the PVY pepper group. As PVY is one of the most economically important plant pathogens in a range of crops, including pepper, these MAbs will provide a useful tool for practical diagnosis and strain identification of PVY.     

Diagnosis of potato virus YN: a comparison between polyclonal and monoclonal antibodies and a biological assay

In an investigation conducted over 5 years, tests of samples from the Scottish Seed Potato Classification Scheme showed that when monoclonal antibodies (McABs) were used with the enzyme-linked immunosorbent assay (ELISA), they reliably detected the tobacco veinal necrosis strain of potato virus Y (PVY^N). Polyclonal antibodies used in the first 3 years of the investigation were unreliable in differentiating PVY^N from the ordinary strain (PVY^N). It is suggested that ELISA and McABs be routinely used to diagnose PVY^N and that all samples which give negative results be further assayed biologically to identify the virus or to indicate strains of PVY^N not detectable by the McAB. Problems encountered with both assay systems are discussed.     

Hydroxyproline-rich glycoprotein accumulation in tobacco leaves protected against Erysiphe cichoracearum by potato virus Y infection

Tobacco cv. Havana 425 acquired resistance to a compatible isolate of Erysiphe cichoracearum after infection by a strain of potato virus Y (PVY^N) that causes veinal necrosis; another common strain (PVY^O) that does not cause necrosis gave less protection. Hydroxyproline-rich glycoproteins (HRGPs), believed to be involved in resistance, were determined by analysing hydroxyproline (Hyp) in purified cell walls. Hyp content increased significantly in PVY^N-protected leaves, compared with untreated controls, 2–4 days after necrotic lesion symptoms developed. No further increase in Hyp was noted in PVY^N-protected leaves after E. cichoracearum challenge. Hyp increases were significantly higher in protected leaves of plants showing symptoms on day 7 than on day 10. Infection with the PVY^O strain caused significant decrease in Hyp content, compared with uninoculated controls. Inoculation of virus-free plants with E. cichoracearum induced moderate and transitory Hyp increases on day 2 or 3, followed by a quick decrease associated with a weak response by the compatible host. It is suggested that HRGP accumulation induced by PVY^N (but not by PVY^O) causes changes in the host cell wall that result in resistance to E. cichoracearum .     

Occurrence of the Andean strain of potato virus S in imported potato material and its effects on potato cultivars

Infection with potato virus S Andean (PVS^A) and ordinary (PVS^o) strains was found in potato breeder's selection No. 8163-511 imported from West Germany; the two PVS strains were differentiated by their reactions on Chenopodium quinoa Tests on potato leaf samples using enzyme-linked immunosorbent assay followed by inoculation to C quinoa were subsequently used to detect PVS^A and PVS^o in a large-scale survey of imported and domestic potato material. PVS^A was detected in breeders' selections and cultivars imported from the Netherlands and West Germany, but not in domestic certified seed potato stocks or farmers' once-grown stocks. PVS^o was found in both imported and domestic certified stocks, but infection was commoner in the imported ones. When plants of C. quinoa, C. amaranticolor, C. murale and Nicotiana debneyi were inoculated with four isolates of PVS^A, one induced mild symptoms while the reactions of the others ranged from moderate to severe. When plants of different potato cultivars were inoculated with three isolates, the plants were mostly infected without symptoms. However, when tubers from some were grown on, the progeny plants of most of the different combinations of cultivar and isolate of PVS^A developed one or more of the following symptoms: vein deepening, rugosity, interveinal chlorosis, premature senescence and early loss of lower leaves.     

马铃薯Y病毒在种薯中检出率及其株系鉴定

 马铃薯是我国重要粮食和经济作物。马铃薯Y病毒(potato virus Y,PVY)是危害马铃薯生产的重要病害。种植脱毒种薯是防治PVY最有效的途径。马铃薯种薯携带PVY问题严重,但种薯中PVY株系还不清楚。本研究利用PVY特异性抗体检测了7个马铃薯品种362个种薯,发现不同品种种薯带毒率差异较大,最高达12%。通过RT-PCR方法扩增获得了7个PVY分离物编码区全序列。重组分析发现7个分离物基因组均为重组型,根据重组位点的差异可以分为PVY^NTN-NW(SYR-II型)、Rec-1、Rec-2和Rec-3等4种重组类型,后3种为新重组类型。系统进化分析发现,分离物HQH18G3-10与PVY^NTN-NW(SYR-II型)处于同一个大的分支,但与中国PVY大田分离物聚集在一起形成一个相对独立的组,命名为PVY^NTN-NW(CN型);其余6个分离物与数据库中的中国分离物聚集在PVY^N-Wi组。这暗示PVY中国分离物具有相对独立的进化过程,PVY马铃薯大田分离物和种薯分离物进化上相近。所有分离物均能在珊西烟上引起典型叶脉坏死症状,HQH18G3-10引起的坏死症状最为严重。本研究首次报道了我国种薯内PVY发生情况,对分析病毒发生发展规律和防控具有借鉴作用。     

马铃薯Y病毒在种薯中检出率及其株系鉴定

马铃薯是我国重要粮食和经济作物。马铃薯Y病毒(potato virus Y,PVY)是危害马铃薯生产的重要病害。种植脱毒种薯是防治PVY最有效的途径。马铃薯种薯携带PVY问题严重,但种薯中PVY株系还不清楚。本研究利用PVY特异性抗体检测了7个马铃薯品种362个种薯,发现不同品种种薯带毒率差异较大,最高达12%。通过RT-PCR方法扩增获得了7个PVY分离物编码区全序列。重组分析发现7个分离物基因组均为重组型,根据重组位点的差异可以分为PVY^NTN-NW(SYR-II型)、Rec-1、Rec-2和Rec-3等4种重组类型,后3种为新重组类型。系统进化分析发现,分离物HQH18G3-10与PVY^NTN-NW(SYR-II型)处于同一个大的分支,但与中国PVY大田分离物聚集在一起形成一个相对独立的组,命名为PVY^NTN-NW(CN型);其余6个分离物与数据库中的中国分离物聚集在PVY^N-Wi组。这暗示PVY中国分离物具有相对独立的进化过程,PVY马铃薯大田分离物和种薯分离物进化上相近。所有分离物均能在珊...     

Interference between potyviruses during aphid transmission

Single aphids ( Myzus persicae ) were allowed sequential access to two leaves which were either free from infection or infected with potato virus Y° (PVY°). PVY^N. beet mosaic virus (BMV), or tobacco mosaic virus (TMV). Aphids given prior or subsequent access to PVY^N-infected leaves transmitted PVY° and BMV less frequently than aphids given prior or subsequent access to virus-free leaves; those given prior or subsequent access to BMV also transmitted PVY° less frequently. However, prior or subsequent access to PVY° did not decrease transmission of either BMV or PVY^N, and access to BMV did not decrease transmission of PVY^N. Access to the non-aphid-transmissible TMV did not affect transmission of either PVY° or PVY^N. PVY^N had the greatest electrophoretic mobility. BMV was least mobile and PVY° was intermediate, so ability to decrease transmission was not directly related to the total anionic charge on the virus particles.     

一株PVYNTN-NW黑龙江马铃薯分离物的检测鉴定

 马铃薯Y病毒(Potato virus Y,PVY)是马铃薯、烟草等茄科作物上的重要病毒,在与寄主共同进化过程中产生了许多株系。本文从黑龙江马铃薯样品中得到PVY分离物A12。ELISA结果表明A12被PVY^O的单克隆抗体特异性识别。A12开放阅读框为9 186个核苷酸,编码3 061个氨基酸,与SYR-II-Be1分离物的核苷酸和氨基酸序列一致率均最高,分别为98.3%和99.2%。系统发育分析发现A12与PVY^NTN-NW株系SYR-II型的分离物聚类到一起;重组分析表明,A12是N-605和O_z的重组体,重组类型与SYR-II-Be1相同。综合以上结果表明,A12属于PVY^NTN-NW株系SYR-II型。但与常见PVY^NTN-NW株系分离物在珊西烟引起叶脉坏死不同,A12产生花叶症状。A12辅助成分-蛋白酶在182位和245位的氨基酸均为精氨酸,而其它PVY^NTN-NW株系分离物为赖氨酸。本研究结果可为黑龙江马铃薯PVY的早期检测和有效防控提供理论指导。     

一株PVYNTN-NW黑龙江马铃薯分离物的检测鉴定

 马铃薯Y病毒(Potato virus Y,PVY)是马铃薯、烟草等茄科作物上的重要病毒,在与寄主共同进化过程中产生了许多株系。本文从黑龙江马铃薯样品中得到PVY分离物A12。ELISA结果表明A12被PVY^O的单克隆抗体特异性识别。A12开放阅读框为9 186个核苷酸,编码3 061个氨基酸,与SYR-II-Be1分离物的核苷酸和氨基酸序列一致率均最高,分别为98.3%和99.2%。系统发育分析发现A12与PVY^NTN-NW株系SYR-II型的分离物聚类到一起;重组分析表明,A12是N-605和O_z的重组体,重组类型与SYR-II-Be1相同。综合以上结果表明,A12属于PVY^NTN-NW株系SYR-II型。但与常见PVY^NTN-NW株系分离物在珊西烟引起叶脉坏死不同,A12产生花叶症状。A12辅助成分-蛋白酶在182位和245位的氨基酸均为精氨酸,而其它PVY^NTN-NW株系分离物为赖氨酸。本研究结果可为黑龙江马铃薯PVY的早期检测和有效防控提供理论指导。     

马铃薯Y病毒中国分离物的分子株系组成

 马铃薯Y病毒(potato virus Y,PVY)主要侵染马铃薯和烟草等茄科作物,给世界农业造成巨大经济损失。本文对测定的23个及GenBank中注册的52个中国PVY分离物ORF序列进行了系统发育、重组和选择压等分析。系统发育分析表明,根据ORF序列可把我国75个PVY分离物和国外30个参比分离物分成O、C、E、NTN-NW(SYR-I型)、NTN-NW(SYR-II型)、NTN(NTN-a型)、NTN(NTN-b型)、NA-N/NTN、Eu-N、N-Wi(N:O型)和N-Wi(N-Wi型)等11个分子株系,其中中国PVY分离物属于除E和C株系外的9个分子株系。除ME162、guiyang、PVYzu、SD-G、WA-13和CN:JL-1:17等 6个分离物基因组中未检测到重组,其余69个分离物均存在明显重组。根据重组位点的不同,中国PVY可分为11种重组类型,其中5种为新的重组类型。选择压分析表明,中国PVY分离物的11个基因均处于负选择,其中核内含体b基因受到的选择压最大,PIPO受到的选择压最小。基因流分析表明,黑龙江、河南和山东PVY分离物间基因交流频繁,马铃薯与烟草PVY分离物之间基因交流频繁。本研究的结果明确了中国PVY分离物的分子株系组成,对指导PVY的检测和防控具有积极作用。     

Characterization of potato Y potyvirus isolates from tomato crops in Islas Canarias (Spain)*

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 PVY^O/C or PVY^N 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.     

Significance of weed hosts for Potato virus Y protection in Syria

A survey of Potato virus Y (PVY) was carried out on weeds growing in and around potato fields in Syria during the autumn growing seasons of 2002, 2004 and 2006. A total of 59 samples of eight weed species and three tobacco ( Nicotiana tabacum ) samples were tested by ELISA using PVY antisera. Among them 15 samples belonged to Solanum nigrum (7 samples), Physalis sp. (6 samples) and tobacco (2 samples) were PVY infected. This suggests that weed hosts and neighbouring tobacco fields are natural reservoirs of PVY in Syria. According to their biological, serological and molecular characteristics, the majority of weed PVY isolates belonged to the PVY^SYR variant indicating a possible correlation between the high incidence of PVY^SYR in potato and weed hosts. This is the first report on the occurrence and characterization of weed PVY isolates from Syria.     

Characterization of a potyvirus from eggplant (Solanum melongena) as a strain of potato virus Y by N-terminal serology and sequence relationships

A potyvirus (eggplant mottle virus, EMoV) causing mosaic mottling in eggplant ( Solanum melongena ) was characterized on the basis of biological, serological and partial nucleotide sequence properties. EMoV infected Chenopodium amaranticolor and members of the Solanaceae. Polyclonal antiserum against EMoV showed antigenic relationship with henbane mosaic potyvirus (HMV) and potato Y potyvirus (PVY). Virus-specific antibodies directed to the N-terminal region of EMoV cross-reacted only with PVY. Determination and comparison of nucleotide sequence of the coat protein (CP) and the 3'-untranslated region (UTR) of EMoV with other potyviruses showed that the level of homology was highest with PVY isolates. Comparative sequence analyses of the CP amino acid and 3'-UTR sequences with distinct PVY isolates placed EMoV within the PVY^O subgroup.     

马铃薯Y病毒HC-Pro第182位赖氨酸残基参与引起烟草叶脉坏死

马铃薯Y病毒(potato virus Y,PVY)是侵染烟草的最重要病毒之一.不同PVY株系侵染烟草可引起不同症状,有些PVY株系可引起烟草叶脉坏死,严重影响烟草的产量和品质.PVY A12分离物属于NTN-NW株系,但侵染珊西烟(Nicoti-ana tabacum cv.Xanthi)不能引起叶脉坏死.分析发现,...     

Impact of the potato inoculation date on potato virus Y load and viral distribution in daughter tubers at harvest

Aged plants are more difficult to infect than young plantlets. This modification of susceptibility is described as mature plant resistance (MPR). For potato virus Y (PVY), MPR is known to lead to low infection rates of plants inoculated at the postflowering stage and a decrease in the number of infected daughter tubers. However, the impact of inoculation date on the capacity of PVY to accumulate in daughter tubers has not been studied so far. Field and greenhouse experiments were carried out to better understand PVY epidemiology and to help potato growers to evaluate consequences of early/late infections on the quality of their crops. In field trials, potato plants (cv. Bintje) were covered by insectproof nets from planting to harvest except for a 14-day period to expose plants to natural PVY infections. Under controlled conditions, potato plants were mechanically inoculated with PVY at different dates from preflowering stages (early inoculations) to postflowering stage (late inoculations). At harvest, daughter tubers were individually collected and analysed to define proportions and viral load of infected tubers according to the time between virus inoculation and harvest. Our results showed that although the age of plants at the time of inoculation can modify their susceptibility to PVY infection, in return, early and late PVY inoculations lead to similar rates of infected tubers at the plant scale and equivalent viral accumulation in infected tubers. All together, these data revealed that both early/late infections are high risks for the sanitary quality of potato tubers.     

In vitro somatic growth and reproduction of phenylamide-resistant and -sensitive isolates of Phytophthora erythroseptica from infected potato tubers in Idaho

Pink rot of potato, most commonly caused by Phytophthora erythroseptica , is a major field and post-harvest problem in southern Idaho, USA, particularly since 1998 when isolates resistant to the phenylamide fungicide metalaxyl-M (mefenoxam) were detected. Isolates of P. erythroseptica were collected from infected tubers in 2001 and 2002 from six Idaho counties and tested for resistance to metalaxyl-M on amended agar. Metalaxyl-M resistant (MR) and metalaxyl-M-sensitive (MS) isolates were identified in six counties; 160 isolates were highly resistant, seven moderately resistant and 57 sensitive to metalaxyl-M with mean EC₅₀ values of 182, 23 and 0·5 mg L⁻¹ ai metalaxyl-M, respectively. Mycelial growth rates and oospore production in agar were assessed for 20 MS and 20 MR isolates at 10, 15, 20, 25 and 30°C. Growth rates of MR isolates were between 2·5 and 3·1 times greater ( P  < 0·05) than those of MS isolates at 10, 15, 20 and 25°C, and oospore production was between 6·8 and 20·5 times greater ( P  < 0·0001) for MR than for MS isolates at the same temperatures. Colony growth in V8 broth at 18°C was greater for MR than MS isolates ( P  < 0·0032). However, zoospore production at 18°C was greater for MS than for MR isolates ( P  < 0·0109), and zoospore production m m ⁻¹ of colony circumference was also greater for MS than for MR isolates, 14 191 and 9959, respectively ( P  = 0·0109). Sexual reproduction of MR isolates in nature may be greater than MS isolates, but MS isolates may be more asexually fit based on the fitness parameters studied.