Virus transmission by aphids in potato crops

This paper reviews the contribution of vector activity and plant age to virus spread in potato crops. Determining which aphid species are vectors is particularly important for timing haulm destruction to minimize tuber infection by potato virus Y (PVY). Alate aphids of more than 30 species transmit PVY, and aphids such asRhopalosiphum padi, that migrate in large numbers before flights of the more efficient vector,Myzus persicae, appear to be important vectors. Differences in methodology, aphid biotypes and virus strains prevent direct comparisons between estimates of vector efficiencies obtained for aphids in different countries in north western Europe. M. persicae is also the most efficient vector of potato leafroll virus (PLRV), but some clones ofMacrosiphum euphorbiae transmit PLRV efficiently toNicotiana clevelandii and potato test plants. The removal of infected plants early in the season prevents the spread of PLRV in cool regions with limited vector activity. The proportion of aphids acquiring PLRV from infected potato plants decreases with plant age, and healthy potato plants are more resistant to infection later in the season. Severe symptoms of secondary leafroll developed on progeny plants of cv. Maris Piper derived from mother plants inoculated with PLRV in June or July of the previous year. Progeny plants derived from mother plants inoculated in August showed only mild symptoms, but the concentration of PLRV in these plants was as high as that in the plants with severe symptoms.     

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.     

Transgenic potato plants expressing the potato virus X (PVX) coat protein gene developed resistance to the viral infection

The gene coding for potato virus X (PVX) coat protein (CP) was expressed in transgenic potato plants obtained byAgrobacterium tumefaciens transformation. One hundred independent clones were analyzed in challenge experiments for resistance to PVX infection under greenhouse conditions as a preliminary test. From this test, 16 clones with the best resistance results were selected for a small-scale field trial. Clones 54, 60, 73 and 91 demonstrated the best values of resistance to PVX in the field. Statistical analysis of the field trial showed significant differences between means of optical density obtained in ELISA from transgenic clones and non-transformed plants (P<0.05). There was correspondence between resistance to virus infection and expression of the CP gene of PVX virus in the analyzed clones. http://www.phytoparasitica.org posting Jan. 21, 2002. Corresponding author [e-mail: vivian.doreste@cigb.edu.cu].     

Virus transmission by aphids in potato crops

This paper reviews the contribution of vector activity and plant age to virus spread in potato crops. Determining which aphid species are vectors is particularly important for timing haulm destruction to minimize tuber infection by potato virus Y (PVY). Alate aphids of more than 30 species transmit PVY, and aphids such asRhopalosiphum padi, that migrate in large numbers before flights of the more efficient vector,Myzus persicae, appear to be important vectors. Differences in methodology, aphid biotypes and virus strains prevent direct comparisons between estimates of vector efficiencies obtained for aphids in different countries in north western Europe.M. persicae is also the most efficient vector of potato leafroll virus (PLRV), but some clones ofMacrosiphum euphorbiae transmit PLRV efficiently toNicotiana clevelandii and potato test plants. The removal of infected plants early in the season prevents the spread of PLRV in cool regions with limited vector activity. The proportion of aphids acquiring PLRV from infected potato plants decreases with plant age, and healthy potato plants are more resistant to infection later in the season. Severe symptoms of secondary leafroll developed on progeny plants of cv. Maris Piper derived from mother plants inoculated with PLRV in June or July of the previous year. Progeny plants derived from mother plants inoculated in August showed only mild symptoms, but the concentration of PLRV in these plants was as high as that in the plants with severe symptoms.     

Effect of temperature on resistance to Potato virus Y in potato cultivars carrying the resistance gene Rychc

The effect of cultivation temperatures on the resistance reaction to three Potato virus Y strains (PVY^O, PVY^N and PVY^NTN) in potato cultivars carrying Ry_chc was examined. When potato plants carrying Ry_chc 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 Ry_chc‐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 Ry_chc. 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 Ry_chc. These results show that Ry_chc confers an extreme resistance to PVY strains occurring in Japan.     

Biological control of potato soft rot caused by Dickeya solani and the survival of bacterial antagonists under cold storage conditions

Dickeya and Pectobacterium are responsible for causing blackleg of plants and soft rot of tubers in storage and in the field, giving rise to losses in seed potato production. In an attempt to improve potato health, biocontrol activity of known and putative antagonists was screened using in vitro and in planta assays, followed by analysis of their persistence at various storage temperatures. Most antagonists had low survival on potato tuber surfaces at 4 °C. The population dynamics of the best low-temperature tolerant strain and also the most efficient antagonist, Serratia plymuthica A30, along with Dickeya solani as target pathogen, was studied with TaqMan real-time PCR throughout the storage period. Tubers of three potato cultivars were treated in the autumn with the antagonist and then inoculated with D. solani. Although the cell densities of both strains decreased during the storage period in inoculated tubers, the pathogen population was always lower in the presence of the antagonist. The treated tubers were planted in the field the following growing season to evaluate the efficiency of the bacterial antagonist for controlling disease incidence. The potato endophyte S. plymuthica A30 protected potato plants by reducing blackleg development on average by 58.5% and transmission to tuber progeny as latent infection by 47–75%. These results suggest that treatment of potato tubers with biocontrol agents after harvest can reduce the severity of soft rot disease during storage and affect the transmission of soft rot bacteria from mother tubers to progeny tubers during field cultivation.     

Reaction of three potato cultivars to potato virus S and alteration of miRNAs and mRNA targets in the resistant genotypes

Reactions of three Polish potato cultivars to potato virus S (PVS) were investigated at 22°C. Cultivars Tajfun and Tonacja exhibited partial resistance with systemic infection detected in some inoculated plants; cultivar Bryza was susceptible to PVS with systemic infection detected in all inoculated plants. The virus was not detectable by ELISA at 23 days postinoculation (dpi) but was detected after 40 dpi. Infection rate and viral accumulation were significantly lower in Tonacja and Tajfun than in Bryza, but no statistically significant difference between Tajfun and Tonacja was detected. Both susceptible and resistant genotypes displayed various, either common or cultivar-specific, symptoms. Delayed systemic infection at 56 dpi was observed in some cases in Tonacja and Tajfun. Resistance-related alteration of a set of miRNAs and mRNA targets in the tested cultivars in response to PVS at 22°C exhibited inter- and intracultivar variability. The majority of tested genes were altered only in the partially resistant Tajfun and Tonacja but not in the susceptible Bryza. Enhanced expression of AGO1-2, DCL1, stu-miR482 and its target Gpa2 was observed in Tonacja and plants of Tajfun in which PVS was detected, with the highest induction of Gpa2 in Tajfun (30.2-fold). However, their expression remained unchanged or decreased in plants of Tajfun in which PVS was undetected. Increased expression of stu-miR168a and stu-miR172e was observed in Tonacja and the PVS-undetected plants of Tajfun, respectively, but not in the PVS-detected plants of Tajfun. This is the first report on cultivar-specific alteration of miRNA in a potato–PVS resistance interaction.     

矿物油和维生素B1对马铃薯病毒病的防效研究

多数马铃薯病毒可以借助蚜虫传播, 并通过块茎世代积累, 导致马铃薯种性退化, 严重影响块茎的产量和品质?为了筛选新型?环保的马铃薯病毒病防治药剂, 本研究通过3个季节的田间试验, 对矿物油?维生素B1和杀虫剂吡虫啉在防治马铃薯病毒病中的效果进行了评价?结果表明, 通过马铃薯出苗后间隔10 d连续3次喷施, 矿物油能够控制马铃薯卷叶病(potato leaf-roll virus, PLRV)的发生, 对马铃薯M病毒(potato virus M, PVM)和马铃薯S病毒(potato virus S, PVS)的平均防效也分别达到66.72%和70.40%, 但对马铃薯Y病毒(potato virus Y, PVY)和马铃薯A病毒(potato virus A, PVA)在不同的年份和季节的防效不稳定, 平均防效为27.34%和65.02%?维生素B1对PLRV?PVM和PVS的防效也比较明显, 分别达83.36%?83.33%和73.32%, 而对PVY同样防效不稳定, 对PVA防效不明显?杀虫剂吡虫啉对PLRV?PVS和PVM的防效也不稳定, 且对PVY和PVA的防效均不显著?本研究中马铃薯X病毒(potato virus X, PVX)发生频率极低, 未进行病毒病的防效比较?综上所述, 矿物油和维生素B1对马铃薯主要病毒病的综合防效较吡虫啉好, 同时它们的增产效果更明显, 产投比高于化学药剂, 值得推广?     

The effect of potato leafroll virus on the biology of Myzus persicae

Since potato leafroll virus multiplies in the green peach aphid,Myzus persicae, the effect of the virus on the biology of its vector was investigated. Observations were made regarding the longevity and the reproduction rate of viruliferous and non-viruliferous aphids on leafroll-diseased and healthy plants ofPhysalis floridana. The same matters were investigated for both viruliferous and non-viruliferous aphids on seedlings of Chinese cabbage (Brassica pekinensis). It was shown that on leafroll-diseased plants ofP. floridana the aphids produced more progeny than on healthy ones, although the average number of progeny produced per day in both cases was almost the same. On healthy Chinese cabbage seedlings there was no difference in average length of the larval and adult stages, number of progeny per aphid, and number of progeny per day, between viruliferous and non-viruliferous aphids. Evidence was obtained that the virus does not influence the development of its vector. Measurements of oxygen consumption of both viruliferous and non-viruliferous aphids point in the same direction.     

Direct infection of potato tubers by the root parasite Orobanche aegyptiaca

Parasitic plants of the Orobanchaceae are known as obligate root parasites that develop haustoria that connect to roots of various host plants. This article describes, for the first time, a case where the root parasite successfully connected to potato tubers, i.e. to the swollen portion of an underground stem rather than to a root. The rhizosphere of Orobanche aegyptiaca and of its host Solanum tuberosum (potato) was carefully examined. In anatomical studies, the adventitious roots were directly connected to potato tubers. Numerous secondary haustoria, which developed along the adventitious roots in close vicinity to the potato tuber, penetrated the tuber epidermis and the perimedullary tuber parenchyma and developed xylem strands that are presumably connected to the minor xylem strands within the tuber cortex. These findings indicate that parasites of the Orobanchaceae that normally attack host roots may also parasitise underground stem tubers.     

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。     

Characterization of Pectobacterium brasiliense strains from potato and vegetables in Israel

Pectobacterium brasiliense (Pbr) infects a wide range of crops worldwide, causing potato blackleg and soft rot and vegetable soft rots. This study aimed to characterize the genetic diversity and virulence variability among 68 Pbr strains isolated from either symptomless potato progeny tubers, diseased potato plants, ware potatoes wash water, or vegetables grown in Israel, as well as strains isolated from symptomless seed tubers grown in Europe, or diseased potato plants grown in France. The collection was typed using PCR and TaqMan real-time PCR analyses, dnaX sequence analysis, pulsed-field gel electrophoresis (PFGE), and pectolytic activity. dnaX phylogeny grouped almost all strains in a common genetic clade related to Pbr, which was distinct from the other Pectobacterium species. PFGE analysis identified two main clusters, including one major group of 47 strains with 95%–100% similarity. Maceration assays on two potato cultivars showed significant differences between strains but with no correlations with the source of the strains nor the status of the host (with/without symptoms). Molecular (dnaX sequences and PFGE profiles) and phenotypic analyses (tuber maceration tests) showed that the tested Pbr strains are not a homogeneous group. Analysis of the tested Pbr strains isolated from potato and vegetables grown in fields with a history of potato cultivation suggests that seed tubers imported from Europe may be the main source for Pbr in Israel. To the best of our knowledge, this is the first study that describes biodiversity and population structure of P. brasiliense isolated from potato and vegetables under hot climate conditions.     

Characteristics of a resistance-breaking isolate of potato virus Y causing potato tuber necrotic ringspot disease

An Austrian isolate of potato virus Y^NTN, the causal agent of potato tuber necrotic ringspot disease (PTNRD), was serologically compared with seven Dutch PVY^N isolates. Using polyclonal and monoclonal antibodies, it was found indistinguishable from PVY^N. Determination of the nucleotide sequence of the coat protein cistron and comparison of the deduced amino acid sequence with coat protein sequences of other potyviruses revealed a high level of homology with PVY^N coat protein sequences. This confirmed the close taxonomic relationship of PVY^NTN with the PVY^N subgroup of potato virus Y. PVY^NTN is able to overcome all resistance genes known so far in commercial potato cultivars. Remarkably, transgenic PVY-protected tobacco plants are also resistant to PVY^NTN infection upon mechanical and aphid-mediated inoculation. These experiments indicate that genetically engineered resistance offers great potential in protection of potato to new aggressive strains of PVY^N.     

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。     

Incidence of potato viruses and characterisation of <Emphasis Type="Italic">Potato virus Y</Emphasis> variability in late season planted potato crops in Northern Tunisia

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 PVY^O-type symptoms following transmission to tobacco and to react only against anti-PVY^O-C antibodies. Typical vein necrosis symptoms were obtained from 31 samples, six of which reacted against both anti-PVY^N and anti-PVY^O-C antibodies showing they contained mixed isolates, while 25 of them reacted only with anti-PVY^N antibodies. An immunocapture RT-PCR molecular test using a PVY^NTN 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 PVY^NTN variants with similar recombinations to the standard PVYNTN-H isolate. This is the first report of the occurrence of the PVY^NTN variant and its high incidence in late season potatoes in Tunisia.     

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,...     

Root infection of potato by Spongospora subterranea: knowledge review and evidence for decreased plant productivity

Information is reviewed on root infection of potato by the plasmodiophorid Spongospora subterranea f. sp. subterranea. This pathogen has long been recognized as the cause of root galls (hyperplasia) and the economically important disease powdery scab on tubers (modified stolons). The significance for plant productivity of the zoosporangium stages of the pathogen in potato roots has only recently begun to be documented. Two experiments are described that assessed effects of S. subterranea root infection on potato plant root function and productivity. A greenhouse experiment measured root function and plant parameters for eight potato cultivars with markedly different susceptibilities to tuber powdery scab. Water uptake and plant growth were reduced by S. subterranea inoculation in all eight cultivars. The magnitudes of these negative effects, and intensities of root hyperplasia, differed among the cultivars, but were not related to respective susceptibilities to tuber powdery scab. A field trial assessed root function and plant productivity for a cultivar (Iwa) that is very susceptible to Spongospora tuber and root diseases. Soil water content beneath uninoculated plants was consistently less than for inoculated plants, indicating that inoculation reduced water uptake (root function). Inoculation reduced shoot and root dry weights, and reduced weight of tubers per plant by 42%. Spongospora subterranea causes three diseases of potato: root membrane dysfunction, root hyperplasia and tuber powdery scab. The root diseases caused by the pathogen are likely to be important both for powdery scab management and for deleterious effects on potato crop yields.     

甘肃省马铃薯主要病毒病发生情况调查

2015年-2016年,在甘肃省10个地市24个马铃薯主栽县(区)146个生态区域(乡镇)采集了757份具有典型症状的马铃薯样品,应用DAS-ELISA法进行检测,筛查6种主要病毒(PVX、PVY、PLRV、PVA、PVS和PVM)。结果表明:631份样品检测到病毒,PVS的检出率最高,达47.03%,PVY次之,为33.82%,PVA最低,只有0.63%;发生复合侵染的病毒主要为PVY+PVS,复合侵染率达到10.13%,三种病毒复合侵染主要是PVY+PVS+PVM;病毒种类和感病程度与品种、地域有关。