Powdery Scab Of Potato Research Articles

Potato powdery scab segmentation using improved GrabCut algorithm

Potato powdery scab is a serious disease that affects potato yield and has widespread global impacts. Due to its concealed symptoms, it is difficult to detect and control the disease once lesions appear. This paper aims to overcome the drawbacks of interactive algorithms and proposes an optimized approach using object detection for the GrabCut algorithm. We design a YOLOv7-guided non-interactive GrabCut algorithm and combine it with image denoising techniques, considering the characteristics of potato powdery scab lesions. We successfully achieve effective segmentation of potato powdery scab lesions. Through experiments, the improved segmentation algorithm has an average accuracy of 88.05%, and the highest accuracy can reach 91.07%. This is an increase of 46.28% and 32.69% respectively compared to the relatively accurate K-means algorithm. Moreover, compared to the original algorithm which could not segment the lesions independently, the improvement is more significant. The experimental results indicate that the algorithm has a high segmentation accuracy, which provides strong support for further disease analysis and control.

Morphological and Molecular Detection of Spongospora subterranea on Plant Harvest in Infected Powder Scab Plots in Antioquia

Potato powdery scab is a disease that negatively affects both roots, causing gall formation, and tubers, resulting in brown pustules. Additionally, it leads to the development of resistance structures that can persist in the soil for several years. Globally, it is one of the most limiting diseases for potato cultivation. This study aimed to identify the species present in areas with a historical occurrence of powdery scab and to evaluate their role as alternative hosts for the pathogen. Samples were collected in the municipalities of Santa Rosa de Osos and La Unión (Ant- Col). The presence of structures (plasmodia and cystosori) associated with the pathogen in the roots was determined using trypan blue staining followed by optical microscopy analysis. Morphological identification revealed twenty-six families with pathogen structures, including Acmella mutisii, Amaranthus dubius, Bidens pilosa, Galinsoga quadriradiata, Holcus lanatus, Hypochaeris radicata, Juncus microcephalus, Oxalis corniculata, Pennisetum clandestinum, Phytolacca bogotensis, Poa annua, Polygonum nepalense, Raphanus raphanistrum, Rumex crispus, Sonchus oleraceus, Trifolium repens, Verbena litoralis, along with Fragaria x ananassa, Solanum tuberosum, and Zea mays. Molecular analysis using RT-PCR for the detection of Plasmodiophoromycetes revealed the presence of Spongospora subterranea in Solanum tuberosum; Polymyxa betae in S. tuberosum, O. corniculata, and T. repens; and Polymyxa graminis in Z. mays. This comprehensive study highlights the importance of crop rotation and weed control to disrupt the pathogen’s lifecycle as effective strategies to mitigate the impact of the disease. It emphasizes the role of alternative hosts and their substantial contribution to elevated inoculum levels.

Development and Evaluation of a Loop-Mediated Isothermal Amplification (LAMP) Method for Detection of the Potato Powdery Scab Pathogen Spongospora subterranea.

Spongospora subterranea is the causal agent of powdery scab of potato (Solanum tuberosum), which can significantly reduce potato quality. In this study, we developed and evaluated a loop-mediated isothermal amplification (LAMP) method for the detection of S. subterranea. A set of LAMP primers named PS-LAMP was designed and tested for specificity and sensitivity. In the specificity test, in silico analysis using the NCBI Primer-BLAST tool indicated that PS-LAMP was specific to S. subterranea. The in vitro tests confirmed specificity, showing that PS-LAMP could produce positive signals from DNA isolated from each of three potato tubers with powdery scab symptoms but did not produce positive signals from DNA isolated from 38 nontarget plant pathogens. The sensitivity of PS-LAMP was tested on both gBlocks and DNA isolated from potato samples with powdery scab symptoms. On gBlocks, the lowest number of copies for a positive LAMP reaction was six, which was similar to results obtained via qPCR, but it was 10 times more sensitive than conventional PCR. On a DNA sample from S. subterranea-infected potato, the lowest amount of template DNA for a positive LAMP reaction was 2 pg, which was incomparable with the sensitivity of qPCR. Considering the convenience of the LAMP technique, as well as the high specificity and sensitivity, this assay can be very useful for plant pathology practitioners and diagnostic labs interested in rapid, accurate, and routine detection of S. subterranea and confirmation of powdery scab disease.

Factors influencing suppressiveness of soils to powdery scab of potato

Factors influencing suppressiveness of soils to powdery scab of potato

Powdery scab of potatoes

Powdery scab of potatoes

Evaluation of Effects of Chemical Soil Treatments and Potato Cultivars on Spongospora subterranea Soil Inoculum and Incidence of Powdery Scab and Potato Mop-Top Virus in Potato.

Spongospora subterranea is a soilborne plasmodiophorid that causes powdery scab in potato. It also transmits potato mop-top virus (PMTV), which causes necrotic arcs (spraing) in potato tubers. Three field experiments were conducted in naturally S. subterranea-infested soil to investigate the effects of two chemicals, Omega 500F (fluazinam) and FOLI-R-PLUS RIDEZ (biological extract), on powdery scab, PMTV, and changes in S. subterranea inoculum with six different potato cultivars. The efficacy of soil treatment with these two chemicals on tuber lesions, root galling, and pathogen population was also assessed in greenhouse trials. The chemical treatments did not reduce powdery scab, root gall formation, or S. subterranea inoculum in the field or greenhouse trials. Postharvest S. subterranea soil inoculum in fields varied across farms and among potato cultivars but the pathogen population consistently increased by the end of the growing season. The evaluated russet cultivars were more tolerant to powdery scab than the yellow- or red-skinned cultivars but all were susceptible to PMTV. In the field, powdery scab indices and soil inoculum changes were positively correlated, while postharvest S. subterranea inoculum was positively correlated with root galling in both greenhouse trials. Powdery scab and PMTV occurred in noninoculated potting mix, indicating that peat-based potting mix is a source for both pathogens. These results demonstrate that chemical management methods currently used by farmers are ineffective, that S. subterranea and PMTV in potting mix can cause severe epidemics in greenhouses, and that potato cultivar choices impact inoculum increases in soil.

Aerial dispersal of Spongospora subterranea sp. f. subterranea, the causal agent of potato powdery scab

Potato powdery scab caused by Spongospora subterranea subsp . subterranea (Sss) causes extensive damage to the quality and marketability of tubers. Disease outbreaks in potatoes grown in virgin soils in south Israel, lead us to the hypothesis that wind-driven inoculum may also be a source of new infections. Wind and ground traps (13 of each type) were positioned near contaminated commercial potato fields with a history of powdery scab in two plots during 2013–14 (‘Nave 5’ and ‘Nave 89’). Quantification of pathogen density in soil/dust was carried out by DNA extraction and qPCR analysis. In ‘Nave 5’ plot, 58 and 45% (December and January, respectively) and 75 and 50% of the ground and wind traps, respectively, were Sss-positive, with no significant differences in Sss concentrations. In ‘Nave 89’ plot, the percentage of Sss-positive traps increased from 31% and 18% in the ground and wind traps, respectively, in February, to 100% in both trap types, in April, with no significant differences. Evaluation of the dispersal distance of Sss inoculum from contaminated fields was examined in soil samples taken from the top layer of the ground in the uncultivated area adjacent to the contaminated commercial potato fields with a history of powdery scab, in two sites (‘Nave 5’ and ‘Shalom 7’) during 2016. All soil samples, taken from uncultivated areas near the infested fields in various distances of up to 750 m, were Sss positive. This study demonstrated that Sss can be dispersed by wind, particularly in an intensive potato production region where contaminated fields exist.

Control of potato powdery scab caused by Spongospora subterranea by foliage cover and soil application of chemicals under field conditions with naturally infested soil

AbstractPowdery scab (PS), caused by Spongospora subterranea, reduces the quality and marketability of potatoes worldwide. Disease symptoms include lesions on the tuber surface and root galling, which may lead to yield losses. In the current study we report a sustainable approach to reduce PS by manipulating soil temperature during tuber initiation. Plant cover with nonwoven fabric significantly reduced PS on tubers by 54%–69% in 2017 and 84%–93% in 2019, compared to the control, and root galling by 96% in 2019, due to an increased average minimum and maximum soil temperature of 1.8 and 4.2 °C in respective years. Additional preplanting soil treatments were also evaluated in naturally infested soil. In 2017, disease incidence and severity were significantly reduced using 2.5 or 5 L a.i./ha fluazinam in broadcast application or in‐furrow, and by 0.375 or 0.75 L a.i./ha flusulphamide applied in‐furrow. In 2019, disease incidence and severity were significantly reduced by the broadcast application of fluazinam, and 75 kg/ha calcium cyanamide, but the latter had a negative impact on yield. Soil fumigation with metam sodium resulted in a 98% reduction in PS. Root galling was significantly reduced by calcium cyanamide, metam sodium, and fluazinam in the 2019 trial only. Foliar application of resistance‐inducing phosphonates combined with fluazinam application had no additive effect on PS incidence and severity. Integrated approaches such as tolerant cultivars, soil testing, preplanting fungicide application, and sustainable means of control such as foliage cover for a short period may be implemented in order to control the disease and minimize damage.

马铃薯微型薯粉痂病综合防治技术

马铃薯微型薯粉痂病综合防治技术

Susceptibility of opium poppy and pyrethrum to root infection by Spongospora subterranea

AbstractSpongospora subterranea, which causes powdery scab of potato, infects a diverse range of plant species. Crop rotation as a powdery scab management tool will be compromised if pathogen hosts exist between potato crops. Opium poppy (Papaver somniferum) and pyrethrum (Tanacetum cinerariifolium) are important crops within intensive vegetable production rotations in NW Tasmania. Measurements of S. subterranea soil inoculum within a commercial field showed pathogen amounts were substantially elevated following an opium poppy crop, which suggested host status. In glasshouse testing, opium poppy and pyrethrum were confirmed as hosts of S. subterranea, with opium poppy the more susceptible of the two. Both species were less susceptible than tomato, a known host. Observations of early growth suggested inoculation impacts on all three plant species, although at 16 (tomato and opium poppy) or 26 (pyrethrum) weeks postinoculation, only tomato had significantly reduced shoot and root development. The role of rotation crops in inoculum persistence and the possible role of S. subterranea as a minor pathogen of nonpotato crops are discussed.

Towards biological control of Spongospora subterranea f. sp. subterranea, the causal agent of powdery scab in potato

Powdery scab of potato, caused by the obligate biotrophic protozoan pathogen Spongospora subterranea f.sp. subterranea (Sss), is a major problem in potato growing areas throughout the world. It results in lesions (scabs) on the surface of the tubers which renders them unmarketable. In recent years there has been an increasing number of reports of the disease, many from new areas. Management of the disease has proved difficult and relies on the integrated application of a range of methods. Biocontrol is not currently used for the management of powdery scab although the results of preliminary studies have been encouraging. This review evaluates the potential for developing a biocontrol strategy for powdery scab.

First Report of Potato Powdery Scab, Caused by Spongospora subterranea f. sp. subterranea, in Cyprus

First Report of Potato Powdery Scab, Caused by <i>Spongospora subterranea</i> f. sp. <i>subterranea</i>, in Cyprus

Effect of Soil Moisture Management on the Development of Potato mop-top virus-Induced Tuber Necrosis.

Potato mop-top virus (PMTV), transmitted by Spongospora subterranea f. sp. subterranea, the causal agent of powdery scab in potato, has become one of the most important tuber necrosis viruses in the United States. The virus has been confirmed in six major potato-producing states in the United States since its identification in 2003. Currently, no control methods are available for PMTV or its vector. A growth-chamber experiment was conducted to investigate the potential of using moisture regime adjustments to manage tuber necrosis caused by PMTV. Two commercial potato cultivars with varying levels of sensitivity to PMTV, 'Dakota Crisp' and 'Ivory Crisp', were grown in soil obtained from a PMTV-infested field. Over the course of the plant growth cycle, plants of each cultivar were subjected to moisture regimes of wet throughout (WT), wet early/dry late (WEDL), dry early/wet late (DEWL), and dry throughout (DT). Soil moisture levels of 90 and 60% field capacity were considered wet and dry, respectively, while early and late refer to first and last 50 days after planting, respectively. Results of visual assessment conducted 3 months after storage showed significant differences in root gall formation, powdery scab on tubers, and PMTV tuber necrosis among moisture regimes. Powdery scab incidence was significantly higher in the WT and DEWL regimes than WEDL and DT regimes. PMTV tuber necrosis incidence did not differ between the WT and DEWL or between DEWL and WEDL moisture regimes. However, PMTV tuber necrosis incidence was significantly higher in WT than under WEDL and DT regimes. The incidence of PMTV tuber necrosis was significantly lower in the DT regime than in the other three moisture regimes. Severity of PMTV tuber necrosis was significantly higher in the WT than the other regimes, which did not differ statistically among themselves. A significant interaction was found between cultivar and moisture regime on root gall formation, with the highest number of galls found on Ivory Crisp grown in the WT moisture regime. A significant correlation was found between powdery scab incidence on tubers and PMTV-induced tuber necrosis incidence. The results of this study provide useful basic information upon which further work can be built for formulating irrigation management schemes that have the potential of reducing the likelihood of powdery scab infection and PMTV-induced tuber necrosis development in potato.

Effect of Powdery Scab Root Galls on Yield of Potato.

Powdery scab of potato, caused by Spongospora subterranea f. sp. subterranea, has increased in incidence since 1981 to become a major concern for potato production in the Columbia Basin of south-central Washington and north-central Oregon. Disease symptoms consist of pustules on the tuber surface and wart-like galls on roots, stolons, and tubers. In the current study, the effect of powdery scab root galls on potato yield was quantified by comparing yields of cultivars susceptible and resistant to root galling grown on soil naturally infested and noninfested with the powdery scab pathogen. Potato tuber yields for the three yield components of yield per plant, number of tubers, and weight of tubers were not negatively affected by powdery scab galls on roots of Umatilla Russet and Shepody, as indicated by yield ratios ≥1.0 in 3 of 4 years, and also by regression analyses in all 3 years. Regression lines with a nonsignificant slope or slopes that significantly increased with gall index also indicated that root galls did not negatively affect yield. Mean tuber weight increased as gall index increased for Umatilla Russet in 2 of 3 years. Consequently, control tactics directed solely at reducing powdery scab galls on roots are not justified economically under conditions encountered in the Columbia Basin of Washington and Oregon states. Effort has been made to develop resistant cultivars and search for soil applied chemicals to reduce root galls.

First Report of Potato mop top virus Causing Potato Tuber Necrosis in Colorado and New Mexico.

Potato mop top virus (PMTV) is considered the type member of the genus Pomovirus. PMTV is an important pathogen of potato vectored by the plasmodiophorid Spongospora subterranea f. sp. subterranea (Sss), which causes powdery scab of potato (1). Sss and PMTV are usually associated with cool and humid environments. PMTV-infected potato tubers generally exhibit internal hollow necrotic spots or concentric rings, and the virus is known to cause significant economic losses in Northern Europe, North and South America, and Asia (4). PMTV in the United States was first reported in Maine (2). Potato (Solanum tuberosum L.) tubers cv. FL2048 and cv. Atlantic were sent to our laboratory from fields in Saguache County in Colorado and in San Juan County in New Mexico, respectively, during the spring of 2013. The tubers from both locations had multiple, internal, concentric, necrotic arcs and circles. Internal tissue with necrotic lesion from six symptomatic tubers from each location were crushed in liquid nitrogen followed by ribonucleic acid extraction using a Total RNA Isolation kit (Promega Corp., Madison, WI). These extracts were tested by reverse transcription (RT)-PCR using three different sets of previously published primers for molecular detection of PMTV. The primer set H360/C819 targeting the coat protein (CP) on RNA 3 of PMTV yielded an amplicon (H360-CO and H360-NM) of 460 bp (4). The second set of primers, pmtF4/pmtR4 (5), amplified a 417-bp product (PMTF-CO and PMTF-NM) in RNA 2, and the third set, PMTV-P9/PMTV-M9 (3), designed to amplify the region encoding an 8-KD cysteine-rich protein in RNA 3 of PMTV, yielded a 507-bp amplicon (PMTV9-CO and PMTV9-NM). The amplicons generated from RT-PCR using all three sets were cloned (PGEMT-easy) and sequenced. Since the sequences from symptomatic tuber extracts from each location were identical to their respective primer sets, a consensus sequence from each primer set was submitted to National Center for Biotechnology Information (NCBI) GenBank. Sequences obtained from the H360/C819 primer set (GenBank Accession Nos. KM207013 and KM207014 for H360-CO and H360-NM, respectively) were 100% identical to the corresponding CP regions of PMTV isolates from North Dakota (HM776172). Sequences from the pmtF4/pmtR4 primer set (KM207015 and KM207016 for PMTF-CO and PMTF-NM, respectively) were 100% identical to the corresponding protein in RNA2 of PMTV isolates from North Dakota (GenBank HM776171), and sequences from the PMTV-P9/PMTV-M9 primer set (KM207017 and KM207018 for PMTV9-CO and PMTV9-NM respectively) were 99% identical to the corresponding protein in RNA3 of PMTV isolates (AY187010). The 100-99% homology of the sequences from this study to the corresponding PMTV sequences published in NCBI confirmed the occurrence of symptoms in the tubers from both Colorado and New Mexico due to PMTV. None of the symptomatic tubers tested positive for Tobacco rattle virus, Tomato spotted wilt virus, Alfalfa mosaic virus, Potato leafroll virus, or the necrotic strains of Potato virus Y by RT-PCR. To our knowledge, this is the first report of PMTV in potato in states of Colorado and New Mexico.

Analysis of Carbohydrate Metabolism Genes of Spongospora subterranea Using 454 Pyrosequencing

Spongospora subterranea, the causal agent of Potato powdery scab, is an important soil-borne obligate protozoan commonly found in Andean soils. This is a serious problem that causes cosmetic damage on the skin of tubers and induces root gall formation, diminishing the yield and commercial value of the potato. Genetic studies on S. subterranea are difficult due to its obligate parasitism, which explains the lack of available knowledge on its basic biology. S. subterranea is a member of the Plasmodiophorida order, a protist taxa that includes other important plant pathogens such as Plasmodiophora brassicae and Spongospora nasturtii. Little is known about the genomes of Plasmodiophorida; however, with the use of Next-Generation Sequencing technologies combined with appropriate bioinformatic techniques, it is possible to obtain genomic sequences from obligate pathogens such as S. subterranea. To gain a better understanding of the biology of this pathogen and Plasmodiophorida in general, DNA sequences from a cystosori-enriched sample of S. subterranea were obtained using 454 pyrosequencing technology. As a first step in understanding the nutritional requirements of S. subterranea as well as its infective and resistance structures, we present a bioinformatic analysis of 24 contigs related to genes involved in the glycolysis, starch, celullose and chitin metabolism. Intron structure and codon usage is also discussed. The genes analyzed in this study are a good source of information for studies aimed at characterizing these enzymes in vitro, as well as the generation of new methods for the molecular detection of S. subterranea in either soils or infected plants.

Genetic variance models for the evaluation of resistance to powdery scab (Spongospora subterranea f. sp. subterranea) from long-term potato breeding trials

Breeding for resistance to soil-borne powdery scab in potato is an important component of the integrated management of this disease. Different genetic variance models within a mixed model framework were applied to data from long-term potato breeding trials, for the genetic evaluation of breeding lines. The multi-environment trial (MET) data came from 12 growing seasons (“years”, synonymous with environments) of New Zealand field trials screening for resistance to powdery scab on potato tubers. Pedigree information on a total of 1,031 genotypes was available. Additive components of the genetic effects were important with narrow-sense heritability estimates (and 95 % confidence intervals) from single-year analyses ranging from 0.26 (0.20, 0.44) to 0.57 (0.53, 0.85). Spatial components estimated from the residual plot effects were not important for most years and even when they were significant, estimates were small. In MET analyses, different variance structures for the genetic effects were tested; a homogeneous correlation model (CORH) gave a better fit to the data than a factor analytic FAk model of order (k), 1 and 2. The year-to-year genetic correlation estimate from CORH was 0.81 and compared with a range of 0.59–0.95 estimated from the FA1 model. There was no strong evidence of non-additive genetic effects with zero or boundary estimates for most years. Models which included the pedigree provided a better fit to the data than models that did not include this relationship information. There was no evidence for genetic improvement in resistance for powdery scab on tubers in the breeding population studied. This suggests that selection pressure for resistance in the past has been weak and greater consideration should be given to selecting parents on empirical breeding values to genetically improve breeding populations for resistance to powdery scab.

First Report of Powdery Scab, Caused by Spongospora subterranea f. sp. subterranea, on Potatoes in Crete, Greece.

In February 2013, severe symptoms of the powdery scab canker type were observed during harvesting at the Mallia area of Heraklio, Crete, Greece, on approximately 20% of the tubers of two commercial smooth skinned potato (Solanum tuberosum L.) field crops (cv. Spunta), of which the seeds had been imported from the Netherlands. Initially, small (up to 2 mm diameter), sunken, purple-brown lesions appeared before harvest on the tubers, followed by pimple-like swellings, which increased in size. As lesions matured, they broke through the tuber skin and developed into shallow depressions. Lesions often expanded in depth and width, forming deep pits and open cankers, eventually destroying considerable amounts of tuber tissue. Light microscopic preparations showed the presence of spongy spore balls with a honeycomb-like spore wall structure. Spore balls were golden brown to brown, oval, circular, elongate, pyriform or irregular in shape, and 54.2 ± 0.93 (36.3 to 79.9) × 47.8 ± 0.82 (31.5 to 72.6) μm. These were composed of aggregates of hundreds of spores that were circular to polygonal in shape, and 4.5 ± 0.06 (3.5 to 5.6) μm in diameter. The morphological characteristics closely resembled those reported for the powdery scab pathogen Spongospora subterranea (Wallr.) Lagerheim f. sp. subterranea Tomlinson. Pathogenicity was confirmed by a lab-based bioassay (3), where spore balls scraped from tuber scab lesions were used to inoculate 20 tomato (cv. Earlypak) bait seedlings, while 20 other seedlings were employed as non-inoculated controls. Zoosporangia of S. subterranea were observed microscopically in root hairs and epidermal cells of all inoculated seedlings but not of any control plants 2 weeks after inoculation. The identity of the pathogen was also confirmed in the original potato samples employing Sss AgriStrip (BIOREBA AG, Reinach, Switzerland), an immunological assay specific for S. subterranea resting spores. In addition, DNA was extracted from infected tubers and the region corresponding to the internal transcribed spacers (ITS) and the ribosomal DNA (rDNA) gene regions was amplified (1). PCR products were purified, direct sequenced, and deposited in GenBank (Accession No. KF208654). In a BLASTn search, the 18S (partial)-ITS1-5.8S-ITS2 (partial) sequence stretch showed 95% similarity to a 509-bp sequence (AF102820.1) of the corresponding S. subterranea gene in GenBank (query coverage 98% and E value 0.0). Based on morphological characteristics, pathogenicity test, immunological assay, and molecular data, it was concluded that the pathogen on potato in Crete is S. subterranea f. sp. subterranea. Powdery scab of potatoes by S. subterranea had been reported earlier in some areas of Greece (Argolida, Attica, Kefallinia, Messenia, and Salonika) (2,4), but without any data confirming the identity of the pathogen. To our knowledge, this is the first record in the island of Crete, and the first confirmed report of this pathogen in Greece. Because S. subterranea f. sp. subterranea is a destructive pathogen of potatoes, its presence in Crete could be of significant concern for commercial growers. Consequently seed import regulations should be strictly enforced.

Mitochondrial genome sequence of the potato powdery scab pathogen Spongospora subterranea

Spongospora subterranea is a soil-borne obligate parasite responsible for potato powdery scab disease. S. subterranea is a member of the order Plasmodiophorida, a protist taxa that is related to Cercozoa and Foraminifera but the fine details of these relationships remain unresolved. Currently there is only one available complete mtDNA sequence of a cercozoan, Bigelowiella natans. In this work, the mitochondrial sequence of a S. subterranea isolate infecting an Andean variety of S. tuberosum ssp. andigena (Diacol-Capiro) is presented. The mtDNA codes for 16 proteins of the respiratory chain, 11 ribosomal proteins, 3 ribosomal RNAs, 24 tRNAs, a RNA processing RNaseP, a RNA-directed polymerase, and two proteins of unknown function. This is the first report of a mtDNA genome sequence from a plasmodiophorid and will be useful in clarifying the phylogenetic relationship of this group to other members in the supergroup Rhizaria once more mtDNA sequences are available.

Occurrence of potato mop-top virus in Northwest of Pakistan

The Northwest of Pakistan is the leading seed potato producing area of the country. The long presence of powdery scab in potato in the region led us to investigate the occurrence of potato mop-top virus (PMTV) in potato cultivars commercially grown in the region. We surveyed the hilly region, particularly Malakand and Hazara divisions, over 3 years i.e. 2010–2012. We found that PMTV is prevalent in Northwest of Pakistan and were detected in almost all potato cultivars commercially grown in the region. The highest mean percent incidence (19.0 %) of the virus was reported from a field in zone F (Abbottabad) followed by 15.6 % in zone G (Manshera) in Hazara division. In Malakand Division (Zone A–E) the incidence was lower (5–12 %) than Hazara Division. We observed an increase in virus incidence in 2012 as compared to 2010 and 2011 in all major potato growing zones. The identity of the virus was confirmed through bait bioassay, enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) in leaves and roots of bait plants, tubers of commercially grown cultivars and also in zoospores of its vector, Spongospora subterranea. Our results indicate that the virus was prevalent in at least 25 (out of 26) sampling locations. We found that internal browning symptoms were positively correlated with the presence of the virus in the tubers when tested through ELISA. The results were further confirmed through RT-PCR in potato tubers with brown arc.