Genetic Resistances to Potato Leafroll Virus, Potato Virus Y, and Green Peach Aphid in Progeny ofSolanum etuberosum

Increasing prevalence of potato leafroll virus (PLRV) and potato virus Y (PVY) has been reported in seed and commercial potato production, resulting in the rejection of potatoes for certification and processing. Host plant resistance to PLRV and PVY and their primary vector, green peach aphid,Myzus persicae, could limit the spread of these viruses. Host plant resistance to PLRV, PVY, and green peach aphid has been identified in non-tuber-bearingSolanum etuberosum (PI 245939) and in its backcross 2 (BC₂) progeny. Resistance to green peach aphid involved a reduction in fecundity and adult aphid size. In addition, one BC₂ individual was identified as possessing a genetic factor that was detrimental to nymph survival. PVY resistance was identified in all five BC₂ progenies evaluated in a field screening under intense virus pressure. PLRV resistance was identified in two of the five BC₂ progeny. This resistance was stable in field and cage evaluations with large populations of viruliferous aphids. Based on the segregation of virus resistances in the BC₂ , PVY and PLRV resistances appear to result from the action of independent genetic mechanisms that reduce the levels of primary and secondary virus infection. Two BC₂ individuals, Etb 6-21-3 and Etb 6-21-5 were identified as having multiple resistances to PLRV, PVY, and green peach aphid derived fromS. etuberosum. This germplasm could prove useful to potato breeders in the development of virus-resistant cultivars.     

Comparison of Straw Mulch,Insecticides, Mineral Oil,and Birch Extract for Control of Transmission of Potato virus Y in Seed Potato Crops

Potato virus Y (PVY) is a major pathogen of potato and transmitted non-persistently by aphids. Aphis fabae is the main vector of PVY in the High Grade Seed Potato Production Area (HG area) in Finland, where the number of aphids and infection pressure with PVY are rather low, but problems with PVY occur in PVY-susceptible cultivars. The aim of the study was to test straw mulch, mineral oil, birch extract, and insecticides for control of PVY in small-scale field experiments and, additionally, at farm level in growers’ fields in the HG area of Finland. The insecticide esfenvalerate reduced the incidence of PVY in the progeny tubers by 29% in one of the 3 years, whereas other chemical treatments or birch extract had no significant effect on PVY incidence. Spraying foliage with mineral oil (Sunoco 11 E/3) reduced the incidence of PVY in 2 years by 43 to 58%, respectively. Straw mulch spread to the field at the time of plant emergence reduced PVY incidence in all 3 years by 50–70%. At farm level, straw mulch reduced the incidence of PVY in the progeny tubers by 25–47%, respectively, in both years tested; however, combining application of straw mulch and mineral oil did not further reduce incidence of PVY. Successful control of PVY in the HG area of Finland using straw mulch may be explained by transmission of PVY early in the growing season at the time of plant emergence and the relatively low number of vector aphids.     

Potato Cultivar and Seed Type Affect the Development of Systemic <Emphasis Type="Italic">Potato virus Y</Emphasis> (PVY<Superscript>N-Wi</Superscript>) Infection

Potato virus Y (PVY) infection is one of the greatest challenges to seed potato production in the United States. To determine how cultivar and seed type affect the development of systemic PVY infection, Russet Burbank and Russet Norkotah Colorado 3 cultivars were grown from two types of pre-nuclear seed (i.e., plantlets and minitubers) and Generation 3 (G3) tubers and challenged with PVY strain Wilga (PVY^N-Wi). Systemic PVY infection was measured by assaying spread of virus from the inoculation site to upper non-inoculated leaves. The Burbank cultivar had a lower incidence of systemic PVY infection compared to the incidence of systemic PVY that developed in the Colorado 3 cultivar. Furthermore, Burbank plants grown from G3 tubers had a lower incidence of systemic PVY infection, as compared to Burbank plants grown from plantlets. Together our results indicate that both cultivar and seed type affect the development of systemic PVY^N-Wi infections post-inoculation.     

Potato Plants Grown from Minitubers are Delayed in Maturity and Lower in Yield,but are not at a Higher Risk of <Emphasis Type="Italic">Potato virus Y</Emphasis> Infection than Plants Grown from Conventional Seed

Potato virus Y (PVY) is the most important virus in North American seed potato (Solanum tuberosum L.) production. Planting virus-free minitubers in place of field-grown seed, which usually has a low PVY incidence, reduces initial PVY inoculum in the field. However, plants grown from minitubers are smaller and emerge later than those grown from conventional seed, which could make them more likely to become infected with PVY. We tested the effects of seed type of three potato cultivars (Dark Red Norland, Goldrush, and Red La Soda) on PVY incidence, tuber yield, and flowering time. The incidence of PVY in plants grown from minitubers did not differ from that of plants grown from conventional seed. Minituber-grown plants produced lower tuber yields than plants grown from conventional seed. Plants from minitubers also emerged and flowered later, but this did not increase their incidence of PVY. Cultivar-specific differences were observed in tuber yield and flowering times, suggesting that this variation may influence PVY incidence more than seed type.     

Factors influencing PVY development and disease expression in three potato cultivars

Studies were performed to investigate factors affecting symptom expression of potato virus Y infection in three potato cultivars, Russet Norkotah, Shepody, and Red LaSoda. Quantitative enzyme-linked immunosorbent assay (ELISA) results revealed few differences in the relative virus titer among cultivars tested. Potato virus Y (PVY) titers developed as rapidly in Russet Norkotah as in Shepody and Red LaSoda. Additional studies were performed to determine the effect of light intensity and infections of PVY and potato virus X (PVX), alone and in combination, on the expression of mosaic symptoms in these three cultivars. Low light intensity (270-330 uE/m²/sec) significantly increased plant heights and severity of mosaic disease among the cultivars compared to high light intensity (100-200 uE/m²/sec). PVX and PVY, as well as the combination of PVX and PVY in the same plant, decreased plant height compared to the uninoculated (healthy) controls. Low light intensity and dual infections of PVX and PVY significantly increased mosaic disease severity in Shepody and Red LaSoda, but not in Russet Norkotah. Results of these studies refute the suggestion that Russet Norkotah is resistant to PVY infection since virus titers in this cultivar are similar to the known susceptible cultivars Shepody and Red LaSoda. These results further suggest that while Russet Norkotah is fully susceptible to infection by PVY, it resists symptom expression.     

Evidence of <Emphasis Type="Italic">Potato virus Y</Emphasis> Spread through Post-Emergence Management Practices in Commercial Potato Fields

Potato virus Y (PVY) transmission was studied in six commercial potato fields in 2015 and 2016 in New Brunswick, Canada. Plants emerged from PVY-positive tubers, or PVY-free plants that were artificially inoculated with PVY shortly after emergence, were used as PVY inoculum plants in the study. In all trials, equal numbers of PVY inoculum plants from each of three strains common in the region, PVY^O, PVY^N:O and PVY^NTN, were used. PVY inoculated into tractor-traffic rows showed 2 to 7 times as much PVY spread to previously virus-free plants by the end of the season (up to 48.5% in one tractor row, compared to a maximum of 16.3% in a distant control row unaffected by tractor traffic). Evidence supporting a hypothesis that tractor traffic enhances PVY transmission through aphid disturbance was observed by PVY spread in both directions along the rows, not biased in the direction of tractor travel, and that the ratio of spread of the three strains was nearly indentical in control and tractor rows. However, the lack of spread to immediately adjacent rows, and statistically significant spatial pattern matching the circumference of tractor wheels specific to each field support the hypothesis that direct mechanical transmission of wounded plant sap could also be a factor in the enhanced PVY transmission.     

Population Growth of Myzus persicae on Potato Plants Infected with Different Strains and Variants of Potato virus Y

Potato virus Y (PVY) is one of the most economically important viruses affecting the potato crop. Several strains of the virus, including PVY^O, PVY^N, recombinant isolates; PVY^N:O (PVY ^N-Wi) and PVY^NTN and several variants of PVY^O have been reported from North American potato-production areas. The green peach aphid, Myzus persicae Sulzer, is a colonizer of potatoes and is considered the most important vector of PVY. The objective of this study was to measure the population growth of M. persicae on potato plants infected with different strains and genetic variants of PVY. The initial population of ten winged adults of M. persicae was allowed to develop on a potted plant for 12 days. Results clearly indicated that infections by different strains and genetic variants of PVY did not influence the population growth of M. persicae on potato plants during this period.     

Resistance to <Emphasis Type="Italic">Potato virus Y</Emphasis> in a Multitrait Potato Breeding Scheme without Direct Selection in Each Generation

In an experimental breeding scheme to improve late blight (Phytophthora infestans) and white potato cyst nematode (Globodera pallida) resistance of tetraploid potato over three generations of crossing and selection, 15 clones survived the final selection, and these were derived from 15 great-grandparents. There was no direct selection for resistance to Potato virus Y (PVY), but 14 out of the 15 great-grandparents were resistant to PVY and three had extreme resistance. Thirteen of the 15 descendants had PVY resistance and one extreme resistance. This was within the range expected for a random (unselected) sample from the genotypes of the great-grandparents. Hence, we found no evidence for any positive or negative association between PVY resistance and the attributes selected. The conclusion is that laborious selection is not required in every generation when many parents have PVY resistance, including some with more than one copy of a PVY resistance gene or resistance at more than one locus. However, in the future, determining the major virus resistance genes present in potential parents in each generation using diagnostic molecular markers would prevent susceptible × susceptible crosses being made and maximise the number of resistant × resistant ones.     

Representation of Potato Virus Y Control Strategies in Current and Past Extension Literature

The aphid-vectored Potato virus Y (PVY) is currently seen as an important limiting factor in the production of potatoes in many countries. Using a content-analysis approach, we investigated the German extension literature for recommendations regarding the control of PVY. Media included articles from periodicals addressing farmers and agricultural textbooks published in the last five decades (1955–2004). In the current literature (1995–2004), the clearly dominating strategy was found to be insecticidal control, although this strategy has been subject to some criticism in the scientific literature. Over the last five decades we also found a strongly increasing representation of insecticidal strategies. Furthermore, over this period of time, information diversity, measured as the number of different strategies proposed per article or per textbook, decreased consistently. Electronic supplementary material The online version of this article () contains supplementary material that is available to authorized users.     

Priming Potato with Thiamin to Control Potato Virus Y

Potato virus Y (PVY) is a major potato pathogen affecting potato yields worldwide. Thiamin, a water-soluble B vitamin (vitamin B₁) has been shown to boost the plant’s immunity, thereby increasing resistance against pathogens. In this study, we tested different concentrations of thiamin (1 mM, 10 mM, 50 mM, 100 mM) and multiple thiamin applications (once, biweekly and monthly) on potato resistance to PVY in Ranger Russet potatoes. Plants were mechanically inoculated with PVY^N:O. This PVY strain is known for causing well-defined foliar symptoms. We collected leaflets weekly through April and May 2015 and tested them with an enzyme-linked immunosorbent assay specific to PVY as well as by real time quantitative RT-PCR. These assays allowed us to determine the presence and level of PVY in different parts of the plants. We found that the highest thiamin concentration treatment (100 mM) produced the lowest virus level in potatoes across all dates and leaflet samples. Also, it was found that multiple applications of thiamin had a positive effect on reducing virus level, especially when thiamin was applied every four weeks.     

Potato Breeding and Seed Production System Development in Russia

First, an extensive literature review was performed with respect to Potato virus Y (PVY) resistance sources and their further utilization in a breeding programme. On the basis of that review we present a scheme of backcrossing and new cultivar creation on the basis of five detected sources of PVY resistance and one source of Potato virus X resistance. Some cultivar pedigrees are presented reflecting the differences in the breeding strategies. Moreover, results of investigations on some polygenic traits such as field resistance against late blight and starch content are presented. For these purposes progenies were screened for suitable recombinant genotypes which were used in further crossings. Also the results of investigations on resistance to the potato golden nematode and on the selection of cultivars suitable for processing are briefly analysed. We also describe a programme of parallel evaluation of identical hybrid populations in different soils and climatic zones. The development of seed potato production systems facilitated the conditions to improve the quality of potato seed material, to increase potato production and to allow Russia to participate in the international potato market. Systems of virus detection, norms and methods of laboratory tests as well as requirements for quality and tolerance levels of different seed classes (generations) were unified and harmonized with European systems.     

Potato leafroll virus and potato virus Y in seed potatoes used to plant the North Carolina crop

Incidence of potato leafroll virus (PLRV) and potato virus Y (PVY) was determined in seed potatoes (Solatium tuberosum) from Canada, Maine, Minnesota, New York, North Dakota, Nebraska, Pennsylvania, and Wisconsin used to plant the North Carolina crop in 1977, 1978 and 1979. Incidence of PLRV ranged from 0–5.2% (X = 0.57%) and for PVY from 0-5.6% (X = 0.62%) from all sources (112 seed lots). All PVY isolates (177) tested from potato caused a very mild veinbanding and mottling onNicotiana tabacum cultivars NC 95 and NC 2326. No serological difference was detected between these isolates and the common strain of PVY from tobacco in North Carolina. Essentially no spread of PVY occurred in three potato fields observed each year of the study.     

Evidence of potato virus Y asymptomatic clones in diploid and tetraploid potato-breeding populations

Potato virus Y (PVY) is a potyvirus affecting potato productivity by reducing yield and quality. To reduce the amount of PVY in potato production systems, state seed certification agencies have established threshold criteria, which simultaneously increase quality. Research has documented several commercial cultivars lacking symptom expression of PVY despite infection. The presence of PVY asymptomatic clones in production and breeding populations is particularly important because it may provide an inoculum source in breeders’ seed and this reduces the efficiency of selection. The objectives of this research were to determine to what extent PVY asymptomatic clones are present in potato-breeding populations, and if PVY expression is influenced by the environment. After exposure to PVY, genotypes from different 2x and 4x populations were evaluated for the presence of PVY both visually and by ELISA assay. PVY asymptomatic genotypes were identified in both 2x and 4x populations. Chi square indicated dependency between PVY symptom expression and (1) ploidy, (2) genetically distinct 4x germplasm enhancement populations, and (3) expression in a north temperatevs. tropical environment using 4x progeny from five half-sib families. Dependency was not found between two 4x genetically related sub-populations and PVY asymptomatic expression. Analysis of variance (ANOVA) indicated that clones within family, families, location, and the interaction of location by clone were significant sources of variation for PVY symptom expression, ELISA, and visual evaluation. PVY asymptomatic clones were present in both 2x and 4x populations with higher frequencies in a north temperate compared to a tropical environment, suggesting that PVY symptom expression may be influenced by the environment.     

马铃薯Y病毒一步RT-PCR检测试剂盒的研制

马铃薯Y病毒(Potato virus Y,PVY)对马铃薯的危害最大,可导致马铃薯退化,降低马铃薯产量。解决这一问题的重要途径就是培养脱毒种薯,但是否完全脱毒需要经过检测才能证实。本研究依据PVY CP基因序列设计合成了一对引物PY1、PY2,以带毒样品植物总RNA为模板,在同一个反应中同时加入反转录和PCR反应所需试剂,反应程序中包括反转录和PCR反应所需条件,进行反应扩增,带毒样品扩增得到340 bp的目的条带,而健康对照无此目的条带,从而建立了PVY的一步RT-PCR检测技术,并组装成试剂盒。该试剂盒具有良好的稳定性和特异性,灵敏度可以检测到带毒植物组织下限的6.25μg,高于ELISA(100μg)和NASH(15μg)的灵敏度,虽然和常规方法的灵敏度相同,但更为快速、简便、易于操作,适合脱毒苗和脱毒种薯生产单位做大量样品的检测。     

Identification of triplex (YYYy) Potato Virus Y (PVY) immune progenitors derived fromSolanum tuberosum ssp.andigena

As part of the International Potato Center’s (CIP) virus resistance breeding strategy, a group of 182 selected clones from intercrosses among duplex Potato Virus Y (PVY) immune progenitors derived fromSolanum tuberosum ssp.andigena (i.e., YYyy × YYyy) was sampled. These clones were test-crossed to the PVY susceptible tester 377964.5 (yyyy) to search for triplex (YYYy) and quadruplex (YYYY) PVY immune potato progenitors. Seedlings of each test-crossed progeny were screened for PVY immunity. Genetic analysis of observed ratios for immunity-susceptibility showed that two of the 182 clones segregated as triplex under the assumption of a random chromatid segregation model. The double reduction coefficient, α, and its standard error were estimated from the experimental data, and had values of 0.1566 and 0.0186 respectively. These results indicated that crossovers take place during meiosis between the locus and the centromere, permitting sister chromatids to migrate to the same pole producing a random chromatid segregation. In the population evaluated, no clone was identified as a quadruplex. The two triplex PVY immune genotypes will produce about 96% of progenies with PVY immunity when mated to PVY susceptible advanced clones or varieties. These progenitors have the potential to provide a durable PVY genetic control and diminish the present impact of this virus on the potato crop. Also, immunity to PVY will significantly simplify the seed production process.     

Seed Potato Production in Poland

The aim of this research was to analyze the regional distribution and quality of potato seed production in Poland from 2007 to 2011. The research was based on 10,559 tuber samples taken for the official post-harvest inspection assessment of seed potato lots. A very detailed map of seed plantation locations in Poland was created at the municipality level. The greatest concentration of seed production was from the northern and southern parts of Pomorskie Province, where many seed potatoes were cultivated, and in the north of the Zachodniopomorskie Province, around the towns of Koszalin and Ko?obrzeg. In both provinces, cultivars which were highly susceptible to PVY were cultivated on nearly half of the area. Over time a clear increase in the production of elite material and a decrease in those certified as the lowest category, CB, were observed. The quality of seed potato material was poorest following the harvest in 2008, because of high levels of virus infection; 30 % of the seed lots were not certified. Potato leaf roll virus (PLRV) was recorded occasionally and it is at present of no economic importance in Poland. The role of potato virus Y (PVY), increased, probably because of the growth in the share of foreign cultivars (mainly Dutch) which are more susceptible to PVY. There were also changes in the populations of PVY strains. The share of Polish cultivars in potato seed production decreased to 36.3 % in 2012.     

How Long can Rogued Potato Plants Left in the Field Be a Source of <Emphasis Type="Italic">Potato Virus Y</Emphasis> for Aphids?

Removal of diseased plants (roguing) is commonly practiced in seed potato production. Diseased plants left to desiccate in fields could possibly serve as sources of Potato virus Y (PVY). PVY acquisition by three aphid species (Myzus persicae, Rhopalosiphum padi, Aphis fabae) was evaluated with leaflets from rogued plants for seven days. Results showed greater PVY acquisition rates in non-colonizing aphids species compared to colonizing ones. The proportion of aphids leaving leaflets increased with time (i.e. days after plants were uprooted) and some aphids were carrying PVY in their stylets on each of the seven days of the experiment, suggesting that aphids were able to probe and acquire PVY even when plants wilted. These results confirmed that diseased plants left in fields can serve as a source of PVY for aphids even after they wilted and emphasises that proper actions must be taken to efficiently remove diseased plants from fields.     

Soybean aphid,Aphis glycines Matsumura, a new vector ofPotato virus Y in potato

Soybean aphid (Aphis glycines Matsumura), an exotic species first discovered in the North Central region of the United States in 2000, is a competent vector of severalPotyviridae. Soybean aphid has high fecundity and produces alatae (winged morphs) readily, characteristics typical of proficient virus vectors. When soybean aphids were exposed toPotato virus Y (PVY)-infected potato plants and then clip-caged on healthy potato plants in groups of five or as single aphids, PVY transmission ranged from 14% to 75% across all experiments. PVY^o, PVYⁿ, and PVP^ntn strains were transmitted by soybean aphid.     

马铃薯病毒外壳蛋白融合基因转化马铃薯及其抗病性分析

将多种病毒的有效核酸片断拼接成融合基因转入马铃薯可获得多抗马铃薯材料。针对马铃薯生产中分布广泛、危害严重并经常混合感染的马铃薯X病毒(PVX)、马铃薯Y病毒(PVY)、马铃薯卷叶病毒(PLRV)和马铃薯S病毒(PVS),开展了利用基因工程方法获得兼抗4种马铃薯病毒转基因马铃薯材料的研究。试验在前期获得含4种马铃薯病毒外壳蛋白基因片段的质粒pART27-XSYV-rh的基础上,通过根癌农杆菌(Agrobacterium tumefaciens)介导转化马铃薯(Solanum tuberosum)品种‘陇薯3号’,PCR扩增和PCR-Southern杂交证明,4价融合基因已整合到马铃薯基因组中。qRT-PCR分析表明,该融合基因在转基因植株中能正常表达。3株转基因植株的抗病性鉴定结果表明,2株对4种病毒同时具有抗性;1株对PLRV侵染表现阳性,对另外3种病毒同时具有抗性。     

Advantages of a soluble dye in blot immunobinding assays for virus detection in potatoes

Summary A technique is described in which plant sap is blotted onto small pieces (8×11 mm) of nylon membrane and virus particles bound to the paper are detected by a modification of the enzymelinked immunosorbent assay (ELISA). The detectable product of the assay is a soluble yellow dye, the absorbance of which increased with the virus content of the plant sap. Leaf or tuber sap from plants secondarily-infected with either potato leafroll virus or potato virus Y could be clearly distinguished from that of healthy plants and a majority of tubers primarily infected with PVY were also detected.