Effects of systemic infections with Tobacco rattle virus on agronomic and quality traits of a range of potato cultivars

Infection of several commercially important potato cultivars with Tobacco rattle virus (TRV) can result in systemic infection with M-type virus, which persists through generations of vegetative propagation, although spraing symptoms in the tubers rarely develop. In field trials of nine such cultivars it was shown that TRV infection can delay plant emergence and retard subsequent growth, reduce tuber yield and mean tuber weight, increase tuber numbers and the proportion of small tubers, increase the incidence of growth cracks and misshapen tubers, diminish dry matter content, and exacerbate after-cooking blackening. Each cultivar was affected differently, showing different combinations and degrees of these effects. Virus concentration in leaf extracts from individual plants was also highly variable. These, and other potato cultivars similarly susceptible to TRV, are grown on large areas of UK and European potato land. The implications of growing such cultivars for the seed, ware and processing sectors of the potato industry are discussed.     

The movement of potato virus Y (PVY) in the vascular system of potato plants

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: PVY^C, PVY^N, PVY^O, PVY^N:O, PVY^NTN, and PVY^N-Wi. Nowadays, PVY^NTN and PVY^N-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 PVY^N is better translocated than PVY^O, 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 PVY^N-Wi translocates more efficiently to progeny tubers than PVY^NTN. 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.     

Comparison between ELISA and bio tin-la belled probes from cloned cDNA of potato virus X for the detection of virus in crude tuber extracts

Diseases caused by potato virus X (PVX) are of significant agronomic importance, and early detection is vital. Biotinylated DNA probes were prepared by random-primed labelling from cDNA inserts and used for the detection of PVX in crude extracts of infected tubers. The minimum detection level in these extracts is in the order of femtograms of PVX RNA. Comparison with ELISA showed that the hybridization method is 100–250 times more sensitive. Probes prepared by this method are highly specific for target RNA even in crude tuber extracts.     

Detection of <Emphasis Type="Italic">Potato virus Y</Emphasis> in industrial quantities of seed potatoes by TaqMan Real Time PCR

Potato (Solanum tuberosum) is the largest crop in Israel. Production is based on the import of seed tubers from Europe for the spring crop. Imported tubers are generally free from virus infection. The most important virus infecting potato is Potato virus Y (PVY), which may cause severe damage to marketable yields. In Israel, tubers from the spring harvest are stored over the summer for planting in the autumn. It is important to be able to determine the infection rate of seed tuber lots from the spring harvest prior to storage. Commonly, infection is measured by sprouting tubers and measuring virus titre in the leaves using ELISA (the “Growing-On test”), which takes at least 6 weeks to give results. There is a need for a faster method to produce results, such as Taqman Real Time PCR (qPCR), for direct analysis of viral infection in tubers at harvest. To use qPCR as a diagnostic tool, it is necessary to demonstrate that both techniques give comparable results on batches of field-grown tubers. Such a comparison was performed on potential seed tuber lots of 14 different cultivars over three Israeli spring harvests (2013–2015). The agreement between the results of the two techniques was not of high statistical significance. However, the qPCR technique can distinguish well, by binary classification, between tuber lots with a low PVY infection rate (<5% by Growing On test; suitable for seed) and those unsuitable for seed (≥5% by Growing On test). Therefore, qPCR is an appropriate technique for determination of the PVY infection rate of seed tuber lots in Israel.     

Partial infection with potato virus YN of tubers from primarily infected potato plants

A field experiment was designed to obtain information on the extent of partial infection of Bintje potato tubers with potato virus Y^N. Data from eight fields, in which plants were artificially infected with the virus, showed that tubers with a weight lower than 30 g became infected only about half as frequently as bigger tubers; the latter were divided into three groups of 30–60 g, 60–90 g and over 90 g, but there were no significant differences in the extent of infection in these groups. In the same experiment it was found that the heel end of a tuber is less frequently infected than the rose end. This means that in testing samples of potato tubers for the presence of potato virus Y^N it is preferable to grow the rose end of the tuber.Samenvatting Een veldproef, waarbij aardappelplanten kunstmatig met aardappel-Y^N-virus werden geïnoculeerd met het doel nadere gegevens te verkrijgen omtrent de gedeeltelijke besmetting van knollen met dit virus, leverde de volgende resultaten op. Het percentage besmette knollen met een lager gewicht dan 30 g bleek ongeveer de helft te bedragen van dat van knollen in de gewichtsklassen 30–60 g, 60–90 g en de klasse zwaarder dan 90 g. Tussen de drie laatstgenoemde groepen traden geen betrouwbare verschillen in besmetting op.Verder bleek dat in alle gewichtsklassen de oogstek genomen van de top van de knol meer kans heeft met Y^N-virus besmet te geraken dan de oogstek genomen van het naveleinde van de knol. Voor de nacontrole van aardappelpoot-goed betekent dit, dat het toetsen van een oogstek van de top van een knol voor dit doel beter geschikt is dan de oogstek van het naveleinde. De knolgrootte speelt hierbij blijkbaar geen rol van betekenis, daar knollen lichter dan 30 g in het algemeen niet voor pootgoed worden gebruikt.     

Effects of removal of leaves and tops on translocation of potato virus X and potato virus YN in potato plants

Removal of leaves from primarily infected plants does not stop translocation of potato virus X and potato virus Y^N from the stem to the tubers in potato plants. In some cases there is evidence that even more virus reaches the tubers. The removal of the top of a potato plant results clearly in a larger extent of infection of the tubers, as was demonstrated in experiments with both viruses. This effect proved to be greater according as the removed top was larger. Removal of leaves and tops apparently changes the physiological behaviour of potato plants in such a way that virus translocation is promoted. This means that in haulm killing, as is applied in seed potato growing, only perfect killing of the stems and leaves can result in stopping virus translocation to tubers; incomplete killing may have the opposite effect.Samenvatting In primair met aardappel-X- en aardappel-Y^N-virus besmette aardappelplanten werd het transport van virus naar de knollen voortgezet na ontbladering van de planten. In enkele gevallen bleek zelfs een zwaardere knolbesmetting op te treden. Het verwijderen van de top van aardappelplanten leidde in proeven met dezelfde virussen tot een sterkere knobesmetting dan in niet getopte planten. Dit gold des te meer naarmate de verwijderde top groter was.Het verwijderen van bladeren en top brengt een zodanige verandering in het fysiologische gedrag van de aardappelplant teweeg dat er een verhoogde mate van virustransport, dus een zwaardere knolbesmetting optreedt. Voor de teelt van pootaardappelen betekenen deze resultaten dat de loofdoding alleen het beoogde doel zal bereiken als een volledige doding van de bovengrondse plantedelen wordt bewerkstelligd.     

Effect of plant genotype, virus isolate and temperature on the expression of the potato tuber necrotic ringspot disease (PTNRD)

The present study shows that a large range of potato cultivars (29/33 tested), widely grown in the world, are susceptible to potato tuber necrotic ringspot disease caused by potato virus Y. The three factors studied in this work, which proved to influence the level of tuber necrosis reaction, were, first, the plant genotype, since varietal behaviour exhibited large differences; second, the virus genotype, since variations of virulence occurred between the four isolates tested; and third, the environmental conditions, as shown by the different rates of tuber necrosis obtained under contrasting conditions of temperature as much during the growing period as during storage. Three of the cultivars tested, Spunta, Maris Piper and Thalassa, failed to produce necrotic tubers, although infected with a virulent tuber-necrosing isolate. This result, following observations on the inheritance of the tuber necrosis trait, suggests that at least a major dominant gene controls this reaction in non-sensitive cultivars. On the other hand, the extreme resistance genes ( Ry ) provide a good resistance to virus infection, thus, preventing tuber necrosis under field conditions.     

甘薯病毒病害SPVD抗性鉴定方法及产量损失估计

为了建立规范、有效的甘薯病毒病害（sweet potato virus disease,SPVD）抗性鉴定方法,于2011—2012连续两年,利用田间人工嫁接病毒接穗的方法对12个甘薯品种进行抗性鉴定和产量损失测定。结果显示,嫁接接种后,接穗成活率接近100%,12个品种都有不同程度发病,病情指数在51.0~95.2之间;感染SPVD的甘薯植株叶绿素含量降低、蔓长缩短;单株薯块产量损失范围在55.1%~97.8%之间。研究表明,供试的12个甘薯主栽品种感染SPVD后均可引起严重的产量损失,且田间人工嫁接病毒接穗是一个有效的SPVD抗性鉴定方法。     

Detection of spore balls of Spongospora subterranea on potato tubers by enzyme-linked immunosorbent assay

A rabbit was immunized with a homogenate of spore balls (cystosori) of Spongospora subterranea which also contained some potato tuber debris. The resultant polyclonal antiserum contained antibodies which reacted against extracts of spore balls and healthy tubers. Antibodies to the tuber debris were removed by incubating the blood serum with an extract from a S. subterranea -free tuber. In enzyme-linked immunosorbent assay (ELISA), the γ-globulin fraction of the absorbed antiserum reacted with dilute tuber extracts containing the equivalent of as little as 0·08 spore balls per ml. The reaction with spore balls was inhibited in high concentrations of tuber sap. Extracts of peel from symptomless tubers which had been stored in contact with scabbed tubers also reacted with the γ-globulin, presumably because the symptomless tubers became contaminated with spore balls. However, spore balls in soil were only weakly detected when high numbers were present. The γ-globulin did not react with the plasmodial stage of the pathogen, or with 15 other micro-organisms tested, including resting spores of Plasmodiophora brassicae.     

Uneven distribution of two potyviruses (feathery mottle virus and sweet potato latent virus) in sweet potato plants and its implication on virus indexing of meristem derived plants

Abstract

The distribution of two sweet potato potyviruses, FMV and SPLV, was assessed in three plants infected with both viruses and in one plant infected with FMV only. All leaves, the top and basal sections of the main stem, and branch sections were tested by ELISA. Both symptomless leaves and leaves showing symptoms including purple rings, chlorotic spots, mottle or discoloration were found to contain the viruses. However, neither could be detected in every leaf or stem piece. SPLV was found in a lower proportion of leaf and stem samples than FMV. This indicates that the two viruses are either very unevenly distributed within sweet potato plants or that the virus concentration in some parts is below the detectable level. Testing of each leaf is recommended for reliable virus indexing of small, meristem‐derived sweet potato plantlets, if the ELISA method is used. Additional indexing of all ELISA‐negative materials by grafting to susceptible indicator plants is nevertheless still necessary.     

腐烂茎线虫在马铃薯不同组织中的数量动态

腐烂茎线虫病是近年来我国马铃薯生产中的一种新病害, 了解腐烂茎线虫的侵染规律对该病害的预防和控制及对马铃薯产量和品质提高具有重要意义。本研究采用盆栽法, 在苗期接种腐烂茎线虫, 研究该线虫在马铃薯不同组织中的数量动态及危害程度。结果显示, 在发芽-幼苗期(播种0 ~ 75 d), 母薯先受到腐烂茎线虫侵染; 在发棵期(播种75 ~ 90 d), 母薯和匍匐茎均检测到腐烂茎线虫; 在结薯期到成熟期(播种90 ~ 105 d), 线虫开始危害新生块茎, 随着块茎膨大危害逐渐加重。在马铃薯成熟期, 症状表现最明显, 新生块茎中线虫数量最多, 可达767.67条/g。不同时期的接种试验表明, 在匍匐茎形成期(播种后70 d)接种, 马铃薯受害最为严重, 发病率达100%, 块茎中线虫密度最高, 达到99.32条/g, 且块茎鲜重最低, 为14.02 g/个。本研究结果可为马铃薯腐烂茎线虫的适时有效防治提供参考。     

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.     

玉米和马铃薯根系分泌物对马铃薯生长的影响

通过溶液培养法获取供体玉米和马铃薯根系分泌物，用来浇灌盆栽受体马铃薯“会-2号”，设单株马铃薯浇玉米根系分泌物（P+M-RE）、单株马铃薯浇马铃薯根系分泌物（P+P-RE）和单株马铃薯浇自来水（CK）3个处理，研究玉米、马铃薯根系分泌物对盆栽马铃薯生长的影响。结果表明：（1）盛花期和成熟期，P+M-RE处理的块茎生物量比P+P-RE增加了42.4%和28.5%，比CK增加了28.8%和8.2%，P+P-R比CK减少了23.7%和28.4%，差异分别为显著和极显著；（2）分枝期、盛花期和成熟期与CK相比，P+M-RE处理地上和地下部分生物量分别提高了8.3%~12.7%和7.5%~45.6%，P+P-RE处理分别降低了1.7%~12.9%和5.5%~20.9%；两处理的茎叶比均比CK低，根冠比在盛花期和成熟期比CK提高了64.1%、42.5%和56.8%、40.0%；(3)观测期内，P+M-RE处理叶片、茎秆、根系和块茎的化感敏感指数RI>0，表现为促进作用，敏感程度为根系>叶>块茎>茎秆；P+P-RE处理根系RI<0，叶片、块茎在分枝期和盛花期RI>0，成熟期为RI<0，整体表现为抑制作用；（4）盛花期马铃薯干物质转移率(DMME)及贡献率（DMCR）P+M-RE处理比CK分别提高了45.6%和48.0%，P+P-RE处理比CK分别提高了30.7%和43.9%。由此说明，玉米根系分泌物对马铃薯地上茎叶和地下根系及块茎生长具有净促进作用，有利于块茎的膨大，而马铃薯根系分泌物对自身地上和地下生长则具有抑制作用，影响了块茎膨大，这为揭示玉米||马铃薯体系增产机制提供了一定的理论依据。     

湖南省马铃薯病毒病发生情况调查

为了解湖南省马铃薯种薯质量和主要病毒病发生情况,2019年-2020年马铃薯秋作和冬作期间,对长沙、益阳、湘潭、澧临等马铃薯生产区的155个马铃薯样品,运用反转录-聚合酶链式反应(RT-PCR)和双抗体夹心酶联免疫吸附检测(DAS-ELISA)技术,筛查6种主要马铃薯病毒,包括马铃薯X病毒Potato virus X(PVX)、马铃薯Y病毒Potato virus Y(PVY)、马铃薯M病毒Potato virus M(PVM)、马铃薯S病毒Potato virus S(PVS)、马铃薯A病毒Potato virus A(PVA)、马铃薯卷叶病毒Potato leaf roll virus(PLRV)。检测结果表明:6种马铃薯病毒病在湖南均有不同程度的发生,单一和两种病毒复合感染植株占比最高,其次是3种病毒复合感染,存在极少数植株复合感染4～5种病毒病情况。在秋作马铃薯中,PVY检出率达到29.41%;PVS和PVA检出率均为27.94%;PVM、PVX、PLRV的检出率分别为20.59%、19.12%、17.65%。在冬作马铃薯中,PVX检出率最高,达到31.03%;其次是PLRV,...     

Reaction of potato cultivars to primary and secondary infection by potato mop-top furovirus and strategies for virus detection1

Potato cultivars in elite seed production in Finland were tested for susceptibility to primary and secondary infection by potato mop-top furovirus (PMTV) in field and pot experiments during 1987 and 1988. The tubers of all 22 cultivars tested became infected under favourable conditions in naturally infested soil, and most of them showed external and internal spraing symptoms when stored first at 18°C for 2 weeks and then 2 weeks at 8°C. The second incubation cycle increased the percentage of tubers manifesting symptoms and the halving of tubers also favoured symptom development. The cultivars most tolerant to primary infection were Pito, Hertha and Record, and the most susceptible were Sabina, Olympia, Saturna and Matilda. The same cultivars, excluding Saturna, were also the most susceptible to secondary infection, which decreased tuber yield up to 37%. The virus could be detected fairly reliably in soils by the bait-plant method, and in the tubers after a repeated cycle of incubation at 18 and 8°C. Electron microscopy and serological methods are useful in both virus detection and identification but they still have severe limitations.     

Direct tuber testing for Potato Y potyvirus by real‐time RT‐PCR and ELISA: reliable options for post‐harvest testing?*

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 PVY^N and PVY^O, 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.     

Detection of the root lesion nematode Pratylenchus penetrans in potato tubers

The root lesion nematode Pratylenchus penetrans parasitizes a wide range of economically important crops, including potato (Solanum tuberosum). Damage by P. penetrans impacts not only the potato yield but can also reduce the tuber quality. Detailed information on tuber infection by P. penetrans is scarce for most cultivars and molecular detection of nematodes from infected tubers is needed. The objective of this study was to assess tuber symptomatology due to P. penetrans infection in 10 potato cultivars and to provide an accurate molecular methodology for nematode detection using tuber peels. Sprouts of certified potato seed from cultivars Agata, Agria, Camel, Désirée, Dirosso, Kennebec, Laura, Picasso, Royata, and Stemster were planted in 2 L pots, and soil was inoculated with 4 P. penetrans/g of soil. Sixty days after inoculation, tubers were harvested, inspected for lesions, and the number of nematodes/g of potato peel assessed. Observations of tubers with symptoms showed the presence of P. penetrans in superficial layers of peels around the lenticels and injured necrotic tissue. Different nematode stages were detected in tubers of all inoculated cultivars, varying from 4 to 46 nematodes/g of potato peel. Species-specific primers showed suitable sensitivity and reproducibility for the detection of P. penetrans in tuber potato peel samples. The molecular detection of P. penetrans directly from tuber peels can facilitate routine nematode inspections of potato seed tubers or cull potatoes for nematode detection, and prevent further dissemination of this species.     

Stem and bulb nematode, Ditylenchus dipsaci, associated with a dry rot of potato tubers

About 10% of the ware-sized tubers from a 1990 potato crop were found to have dry rot. The affected tubers had well defined circular patches of dry rot, either with the tuber surface depressed and cracked, or with deep, open cavities where the tuber surface had disintegrated. The rotted tissues contained large numbers of the stem and bulb nematode, Ditylenchus dipsaci. This is the first recorded case in the UK; dry rot of potato tubers is usually caused by the potato tuber nematode D. destructor.