Diversity of Genetic and Vegetative Compatibility Group of Isolates from Chile Using Amplified Fragment Length Polymorphism Markers.

(Wallr.) Hughes is an asexual fungus with five vegetative compatibility groups. It was postulated that was isolated at the center of origin of potato at one time, and due to the movement of potato around the globe, the fungus was established on each continent but became bottlenecked and genetically unable to form stable heterokaryons via vegetative compatibility grouping (VCG) studies.

Aggressiveness of Small-Spored spp. and Their Sensitivity to Succinate Dehydrogenase Inhibitor Fungicides.

Brown leaf spot of potato is caused by a number of small-spored spp. , , and have been reported with increasing frequency in commercial potato fields. Potato cultivars with resistance to small-spored spp.

Phylogenetics of tobacco rattle virus isolates from potato (Solanum tuberosum L.) in the USA: a multi-gene approach to evolutionary lineage.

Tobacco rattle virus (TRV) is an important soil-borne virus of potato that is transmitted by stubby-root nematodes. TRV causes corky ringspot, a tuber disease of economic importance to potato production. Utilizing protein-coding regions of the whole genome and a range of computational tools, the genetic diversity, and population structure of TRV isolates from several potato-growing regions (Colorado, Idaho, Indiana, Minnesota, Nebraska, North Dakota, and Washington State) in the USA were determined.

Impact of SDH Mutations in on Recently Developed SDHI Fungicides Adepidyn and Solatenol.

Early blight, caused by , is observed annually in all midwestern potato production areas. The use of foliar fungicides remains a primary management strategy. However, has developed reduced sensitivity or resistance to many single-site fungicides such as quinone outside inhibitor (QoI, FRAC group 11), succinate dehydrogenase inhibitor (SDHI, FRAC group 7), demethylation inhibitor (DMI, FRAC group 3), and anilinopyrimidine (AP, FRAC group 9) fungicides.

Detection and Quantification of Sporosori in Soil by Quantitative Real-Time PCR.

Powdery scab on potato tubers is caused by the obligate soilborne biotroph and is known to cause substantial losses in potato production. The pathogen also infects roots of susceptible hosts, forming galls which can negatively affect root function. is also the vector of , which causes a tuber necrosis disease that can, depending on temperature and cultivar, render potato tubers unmarketable.

Assessment of Factors Associated with Molecular Quantification of Stubby Root Nematode from Field Soil DNA.

Factors relating to SYBR Green-based quantitative real-time PCR (qPCR) quantification of stubby root nematode using soil DNA were evaluated in this study. Soils used were loamy sand from potato fields in North Dakota and Idaho. Results showed that the largest nematode individuals (body length >720 µm) produced significant lower Cq values than the smallest individuals (<359 µm), indicating more total DNA amount in the largest nematodes.

Quantifying Control Efficacy of Fungicides Commonly Applied for Potato Early Blight Management.

Early blight is an economically important foliar disease of potato in the United States. Because of the lack of resistant potato cultivars, fungicides are applied extensively to obtain adequate control. To manage early blight, standard protectant fungicides and single-site mode-of-action "specialty" fungicides are applied either alone or incorporated into a fungicide rotation program.

Development and Application of a Real-Time Reverse-Transcription PCR and Droplet Digital PCR Assays for the Direct Detection of in Soil.

(PMTV) is a continuing threat to potato production throughout the world. It has the potential to persist in the soil for long periods in the sporosori of its vector f. sp.

Assessing Potato Cultivar Sensitivity to Tuber Necrosis Caused by Tobacco rattle virus.

Tobacco rattle virus (TRV) causes the economically important corky ring spot disease in potato. Chemical control is difficult due to the soilborne nature of the TRV-transmitting nematode vector, and identifying natural host resistance against TRV is considered to be the optimal control measure. The present study investigated the sensitivity of 63 cultivars representing all market types (evaluated at North Dakota and Washington over 2 years) for the incidence of TRV-induced tuber necrosis and severity.

Spatial and Temporal Distribution of Mutations Conferring QoI and SDHI Resistance in Alternaria solani Across the United States.

The application of succinate dehydrogenase inhibiting (SDHI) and quinone outside inhibiting (QoI) fungicide chemistries is a primary tactic in the management of early blight of potato, caused by Alternaria solani. Resistance to QoIs in A. solani has been attributed to the F129L mutation, while resistance to SDHIs is conferred by five different known point mutations on three AsSdh genes.

Potential Impact of Fluopyram on the Frequency of the D123E Mutation in Alternaria solani.

Succinate dehydrogenase-inhibiting (SDHI) fungicides have been widely applied in commercial potato (Solanum tuberosum L.) fields for the control of early blight, caused by Alternaria solani Sorauer. Five-point mutations on three AsSdh genes in A.

Parasitic Fitness of Fungicide-Resistant and -Sensitive Isolates of Alternaria solani.

Resistance to chemistries of the succinate dehydrogenase inhibiting (SDHI) and quinone outside inhibiting (QoI) fungicides has developed rapidly in populations of Alternaria solani, the cause of early blight of potato. Reduced sensitivity to the anilinopyrimidine (AP) fungicide pyrimethanil has also been identified recently, determining that resistance to three chemical classes of fungicides is present within the A. solani population.

Assessing Potato Cultivar Sensitivity to Tuber Necrosis Caused by Potato mop-top virus.

Potato mop-top virus (PMTV) causes mop top disease in potato. This disease can result in a decline in tuber quality causing economic losses to growers due to the production of necrotic lesions and discolored tissue in infected tubers. Due to the soilborne nature of PMTV, identifying and developing host resistance against the virus is considered the best disease management option.

Developing a One-Step Multiplex PCR Assay for Rapid Detection of Four Stubby-Root Nematode Species, Paratrichodorus allius, P. minor, P. porosus, and Trichodorus obtusus.

Four trichodorid species, Paratrichodorus allius, P. minor, P. porosus, and Trichodorus obtusus, were found in multiple states in the United States.

Molecular Characterization and Identification of Stubby Root Nematode Species From Multiple States in the United States.

Stubby root nematodes (SRN) are important plant parasites infecting many crops and widely distributed in many regions of the United States. SRN transmit Tobacco rattle virus, which causes potato corky ringspot disease, thereby having a significant economic impact on the potato industry. In 2015 to 2017, 184 soil samples and 16 nematode suspensions from North Dakota, Minnesota, Idaho, Oregon, Washington, South Carolina, North Carolina, and Florida were assayed for the presence of SRN.

Assessments of Temporal Variations in Haplotypes of 'Candidatus Liberibacter solanacearum' and Its Vector, the Potato Psyllid, in Potato Fields and Native Vegetation.

The potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), had been known for nearly a century to cause psyllid yellows of solanaceous crops. However, it has only been a decade since the insect was discovered to transmit the bacterium 'Candidatus Liberibacter solanacearum' (Lso), which putatively causes potato zebra chip disease. This project was initiated to quantify temporal incidences of haplotypes of the psyllid (Central, Southwestern, and Western) and Lso (A, B) in potato fields and in native vegetation.

Beta Regression Model for Predicting the Development of Pink Rot in Potato Tubers During Storage.

Pink rot is an important disease of potato with worldwide distribution. Severe yield and quality losses have been reported at harvest and in postharvest storage. Under conditions favoring disease development, pink rot severity can continue to increase from the field to storage and from storage to transit, causing further losses.

Individual Participant Data Meta-Analysis of Foliar Fungicides Applied for Potato Early Blight Management.

Foliar fungicides continue to be the primary means of early blight management on potato in the United States. Both premium-priced, single-site mode-of-action "specialty" fungicides and standard protectant multisite fungicides are applied, either alone or incorporated into fungicide rotation programs to combat early blight. Individual participant data meta-analysis was conducted to compare overall fungicide efficacy against early blight on potato, quantify tuber yields, and identify the most efficacious timing for fungicide applications.

Etiology of a Tuber Rot and Foliar Blight of Potato Caused by Phytophthora nicotianae.

Although Phytophthora nicotianae is not normally considered to be an important pathogen of potato (Solanum tuberosum), intermittent outbreaks of a foliar blight and tuber rot have been reported in the United States over the past 75 years. Due to the sporadic nature of these reports, little is known about the etiology of the disease in potato. However, foliar disease and tuber rots caused by this pathogen are usually centered near areas of standing water in the field and along pivot tracks.

Genomes of 'Candidatus Liberibacter solanacearum' Haplotype A from New Zealand and the United States Suggest Significant Genome Plasticity in the Species.

'Candidatus Liberibacter solanacearum' contains two solanaceous crop-infecting haplotypes, A and B. Two haplotype A draft genomes were assembled and compared with ZC1 (haplotype B), revealing inversion and relocation genomic rearrangements, numerous single-nucleotide polymorphisms, and differences in phage-related regions. Differences in prophage location and sequence were seen both within and between haplotype comparisons.

Aspects of pathogen genomics, diversity, epidemiology, vector dynamics, and disease management for a newly emerged disease of potato: zebra chip.

An overview is provided for the aspects of history, biology, genomics, genetics, and epidemiology of zebra chip (ZC), a destructive disease of potato (Solanum tuberosum) that represents a major threat to the potato industries in the United States as well as other potato-production regions in the world. The disease is associated with a gram-negative, phloem-limited, insect-vectored, unculturable prokaryote, 'Candidatus Liberibacter solanacearum', that belongs to the Rhizobiaceae family of α-Proteobacteria. The closest cultivated relatives of 'Ca.

Tuber Rot of Potato Caused by Phytophthora nicotianae: Isolate Aggressiveness and Cultivar Susceptibility.

A study was undertaken in 2008 and 2009 to examine potato (Solanum tuberosum) cultivar susceptibility, the potential of other host species to act as sources of inoculum for potato infections, and other aspects of potato-Phytophthora nicotianae interactions. Twelve isolates of P. nicotianae collected from five leaf, one petiole, and six tuber infections of potato from five states, as well as isolates from a variety of other host species, were evaluated for ability to cause tuber rot of potato via inoculation studies.

A Two-Step Molecular Detection Method for Pyrenophora tritici-repentis Isolates Insensitive to QoI Fungicides.

Tan spot, caused by Pyrenophora tritici-repentis, is an important disease of wheat worldwide. To manage tan spot, quinone outside inhibitor (QoI) fungicides such as azoxystrobin and pyraclostrobin have been applied in many countries. QoI fungicides target the cytochrome b (cyt b) site in complex III of mitochondria and, thus, pose a serious risk for resistance development.

Effect of Application Method and Rate on Residual Efficacy of Mefenoxam and Phosphorous Acid Fungicides in the Control of Pink Rot of Potato.

Experiments were conducted to examine the effectiveness of rate and method of phosphorous acid application for controlling pink rot of potato (Solanum tuberosum) caused by Phytophthora erythroseptica. Replicated small-plot and replicated split commercial field trials were established in commercial production fields in Minnesota from 2006 to 2009. Fungicides were applied in-furrow at planting, or as one, two, or three foliar applications via ground sprayer, irrigation system (chemigation), or fixed-wing aircraft.

Competitive Parasitic Fitness of Mefenoxam-Sensitive and -Resistant Isolates of Phytophthora erythroseptica under Fungicide Selection Pressure.

A 2-year field and laboratory experiment was initiated to study the competitive parasitic fitness of mefenoxam-resistant (50% effective concentration [EC] > 100 μg ml) and mefenoxam-sensitive (EC = 0.07 μg ml) isolates of Phytophthora erythroseptica with equal aggressiveness. The competitive ability of the mefenoxam-resistant and -sensitive isolates was tested under no selection pressure (nonfungicide treated) as well as under the influence of mefenoxam and non-mefenoxam (phosphorous acid) fungicides.