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Meloidogyne chitwoodi is one of the most devastating pests of potato in the U.S. Pacific Northwest (PNW). Nematode-infected tubers develop external as well as internal defects, making the potato tubers unmarketable, and resulting in economic losses. Draft genome assemblies of three M. chitwoodi genotypes—race 1, race 2 and race 1 pathotype Roza—were generated using Illumina and PacBio Sequel RS II sequencing. The final assemblies consist of 30, 39, and 38 polished contigs for race 1, race 2 and race 1 pathotype Roza, respectively, with average N50 of 2.37 Mb and average assembled genome size of approximately 47.41 Mb. On average, 10,508 genes were annotated for each genome. Benchmarking universal single-copy ortholog (BUSCO) analysis indicated that 69.80% of the BUSCOs were complete whereas 68.80, 0.93, and 12.67% were single copy, duplicated, and fragmented, respectively. These highly contiguous genomes will enrich resources to study potato–nematode interactions and enhance breeding efforts to develop nematode-resistant potato varieties for the PNW. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Meloidogyne chitwoodi is a major threat to potato production in the Pacific Northwest region of United States. Infected tubers are rendered unmarketable, hence growers’ profitability is adversely affected. Breeding for nematode resistance is a long-term process and phenotyping the segregating populations for nematode resistance is the most time-consuming and laborious part of the process. Using DNA-based markers closely linked to the nematode resistance trait for marker-assisted selection (MAS) could enhance breeding efficiency and accuracy. In the present study, a pool of phenotyped progenies segregating for nematode resistance and susceptibility were fingerprinted using a 21K single nucleotide polymorphism (SNP) array. Eight candidate SNPs located on potato Chromosome 11, segregating with the nematode resistance trait were identified and used as landmarks for discovery of other marker types such as, simple sequence repeat (SSR) and insertion-deletion (INDEL) markers. Subsequently, a total of eight SNPs, 30 SSRs and four INDELS located on scaffold 11 of Solanum. bulbocastanum were used to design primers; markers were validated on a panel of resistant and susceptible clones. Two SNPs (SB_MC1Chr11-PotVar0066518 and SB_MC1Chr11-PotVar0064140), five SSRs (SB_MC1Chr11-SSR04, SB_MC1Chr11-SSR08, SB_MC1Chr11-SSR10, SB_MC1Chr11-SSR13 and SB_MC1Chr11-SSR20) and one INDEL (SB_MC1Chr11-INDEL4) markers differentated between the resistant and susceptible clones in the test panel as well as other segregating progenies using simple PCR technique and high resolution melting curve analysis. These markers are robust, highly reproducible and easy to use for MAS of nematode resistant potato clones to enhance the breeding program.

We compared the prognosis of inpatients with a known diagnosis of Alzheimer's or Parkinson's disease who have COVID-19 infection with other hospitalized patients with COVID-19. Our cohort study started in October 2020 and ended in May 2021 and included inpatients with COVID-19 infection who were admitted to hospitals. From a total of 67,871 patients with a confirmed diagnosis of COVID-19, a sample of 3732 individuals were selected of which 363 had Alzheimer's, and 259 had Parkinson's disease. All patients had both positive RT-PCR test and positive chest CT for COVID-19. The outcome was dead within 28 days of admission and the predictors were a large number of demographic and clinical features, and comorbidities recorded at patients’ bedside. Mortality were 37.5%, 35.1%, and 29.5% in patients with Alzheimer's disease, Parkinson's disease; and in other patients, respectively. The hazard ratio for Alzheimer's disease was 1.27 (95% CI, 1.06–1.53, p = 0.010) and for Parkinson's disease was 1.17 (95% CI, 0.94–1.46, p = 0.171). Age was a predictor of mortality, hazard ratio = 1.04 (95% CI, 1.03–1.05, p

The Pacific Northwest (PNW) of the United States (Idaho, Oregon, and Washington) is a diverse agricultural production area with over 400 different commodities grown in the region. Plant-parasitic nematodes are a constraint to the production of many of these commodities. Soil sample data from 2012 to 2016 were obtained from nematode diagnostic laboratories in the region to assess trends in occurrence, population densities, and distribution of plant-parasitic nematodes in the PNW. A total of 38,022 unique data points were analyzed. The number of plant-parasitic nematode samples processed in the PNW by diagnostic laboratories has significantly increased from 2012 to 2016. Fifteen genera of plant-parasitic nematodes were identified by diagnostic laboratories, with 86% of the samples in the PNW containing at least one plant-parasitic nematode genus. These laboratories provide a valuable service to agriculture in the PNW. Additionally, they serve as a rich source of information on plant-parasitic nematode distribution, occurrence, and abundance that, when analyzed, provides an empirical basis upon which to interpret individual grower reports and make management recommendations.

Corky ringspot (CRS) is a widespread potato tuber necrotic disease caused by Tobacco rattle virus (TRV) infection. In the Pacific Northwest, this virus is transmitted by the stubby root nematode (SRN) within the genus Paratrichodorus. Remediating CRS affected fields is a major challenge that can be mitigated by growing plant varieties that are resistant to TRV infection. Growing alfalfa has been shown to reduce TRV levels in CRS infested fields over time but the development of a potato cultivar with these same capabilities would be of great economic benefit to potato growers. Castle Russet is a new potato clone that does not develop symptoms of CRS disease. To assess its ability to reduce soil virus load, Castle Russet, tobacco var. "Samsun NN", alfalfa var. "Vernema", and Russet Burbank potato were grown for a period of 1 to 3 months in soils containing viruliferous SRN populations at two different inoculation pressures (60 nematodes/pot and 1060 nematodes/pot) in greenhouse pot experiments. SRN population size and the presence of TRV were assessed over several months post inoculation. Results indicate that plant host and length of exposure significantly influence SRN population dynamics, whereas the TRV infection status of bait plants was significantly affected by both of these factors as well as inoculation pressure. These results suggest that both alfalfa var. "Vernema" and Castle Russet are resistant to TRV infection and may potentially be used to eliminate the virus from fields affected by CRS. Corky ringspot (CRS) is a widespread potato tuber necrotic disease caused by Tobacco rattle virus (TRV) infection. In the Pacific Northwest, this virus is transmitted by the stubby root nematode (SRN) within the genus Paratrichodorus. Remediating CRS affected fields is a major challenge that can be mitigated by growing plant varieties that are resistant to TRV infection. Growing alfalfa has been shown to reduce TRV levels in CRS infested fields over time but the development of a potato cultivar with these same capabilities would be of great economic benefit to potato growers. Castle Russet is a new potato clone that does not develop symptoms of CRS disease. To assess its ability to reduce soil virus load, Castle Russet, tobacco var. “Samsun NN”, alfalfa var. “Vernema”, and Russet Burbank potato were grown for a period of 1 to 3 months in soils containing viruliferous SRN populations at two different inoculation pressures (60 nematodes/pot and 1060 nematodes/pot) in greenhouse pot experiments. SRN population size and the presence of TRV were assessed over several months post inoculation. Results indicate that plant host and length of exposure significantly influence SRN population dynamics, whereas the TRV infection status of bait plants was significantly affected by both of these factors as well as inoculation pressure. These results suggest that both alfalfa var. “Vernema” and Castle Russet are resistant to TRV infection and may potentially be used to eliminate the virus from fields affected by CRS.

Meloidogyne chitwoodi (Columbia root-knot nematode, CRKN) can cause serious damage in potato production systems, decreasing tuber value in the fresh market and processing industries. Genetic resistance to CRKN was first identified from the wild diploid potato species Solanum bulbocastanum accession SB22 and was successfully introgressed into tetraploid potato breeding material. To expand the base of genetic resistance, 40 plant accessions representing nine wild potato species were screened for their resistance to M. chitwoodi. Greenhouse screening identified fifteen clones from S. hougasii, one clone from S. bulbocastanum, and one clone from S. stenophyllidium with moderate to high levels of resistance against three isolates of M. chitwoodi. Geographical mapping showed that the resistance sources identified in this and previous studies primarily originated in the states of Jalisco and Michoacan in west-central Mexico. These new sources of resistance will be introgressed into elite potato populations to facilitate the development of potato cultivars with durable resistance to M. chitwoodi.

In June 2006, stunted and chlorotic plants were observed in large patches in two 40.5-ha fields of dryland peas (Pisum sativum) in Latah County, Idaho, which resulted in 90 and 75% crop loss. In the same region, a 121.4-ha field of dryland lentils (Lens culinaris) also had plants showing poor growth, wilting, and yellowing in large patches, which resulted in 40% crop loss. Two species of lesion nematodes (Pratylenchus neglectus and P. thornei) and one species of pin nematode (Paratylenchus hamatus) were extracted from rhizosphere soil and the roots of symptomatic plants from these fields. In a subsequent survey of seven dryland pea fields, under cv. Columbian, in Latah and Nez Perce counties and one dryland pea field, under cv. Small Sieve, in Latah County, plant samples had means of 551 and 2,178 mixed species of lesion nematodes per gram of dry root, respectively. Plant samples from 12 lentil fields in Latah County, six planted with cv. Red Chief and six with cv. Pardina, had means of 279 and 987 mixed species of lesion nematodes per gram of dry root, respectively. Soil samples from the same fields had a mean of 628 and 671 pin nematodes, Paratylenchus hamatus, per 250 cm3 soil for Red Chief and Pardina, respectively. Lentils cv. Pardina and peas cv. Columbian were planted separately in six pots, five seeds per pot containing 250 g of infested soil brought from the field to the greenhouse. Fumigated sandy loam soil was used as control. These assays were repeated three times. In addition, peas and lentils were planted to pots infested singly with each of the three nematode species. For this assay, nematodes were extracted from field soil, surface sterilized, and used to infest 250 g of fumigated sandy loam soil at two nematodes per gram of soil. Six plants per nematode species and an uninoculated control were used in the greenhouse assays, which were repeated three times. Nematodes in all of the assays reduced plant growth in comparison with controls; an average of 50 to 70% reduction in plant height was noted. The lesion nematode populations increased in all pots. The greenhouse assays verified the negative impact of these nematodes on growth of dryland peas cvs. Columbian and Small Sieve and lentils cvs. Red Chief and Pardina. P. neglectus, P. thornei, and Paratylenchus spp. previously have been reported from the semi-arid Pacific Northwest (1). However, to our knowledge, this is the first report attributing plant growth and yield reduction of certain cultivars of lentils and peas to these two species of lesion nematodes and pin nematodes, identified to species level as Paratylenchus hamatus. Reference: (1) R. W. Smiley et al. J. Nematol. 36:54, 2004.

Dagger nematode, Xiphinema rivesi Dalmaso, 1969 reportedly transmits several viruses in North America and Europe (2) leading to severe yield reduction in crops. Soil samples were collected in March 2013 during a survey of cherry orchards in Chelan County, WA; these historically suffer from cherry rasp leaf disease, caused by Cherry rasp leaf virus (CRLV) (genus Cheravirus). Soil samples were transported to the WSDA nematology laboratory in Prosser, WA, where 250-cc subsamples were processed using sucrose centrifugal flotation (1). Dagger nematodes were hand-picked and stored in 0.1% sodium chloride before being sent to the USDA-ARS Nematology Laboratory in Beltsville, MD, for morphological and molecular identification. The morphological and molecular analysis of adult females identified the dagger nematode species as Xiphinema rivesi Dalmaso, 1969 (4). Morphological characters used for identification included female body, and total stylet length (odontostyle and odontophore), location of guiding ring from oral aperture, head and tail shape, various tail measurements, and vulva percentage in relation to body length. Measurements of females (n = 10) include a mean body length of 1,902 ± 162.4 (1,832 to 2,203) μm, odontostyle 83 ± 3.5 (80 to 90) μm, odontophore 54.8 ± 4.2 (50 to 65) μm, total stylet 137.8 ± 4.2 (130 to 145) μm, guiding ring from oral aperture 70 ± 5.1 (60 to 75) μm, tail 30.8 ± 2.5 (27.5 to 35.0) μm, body diameter at anus 24.7 ± 1.7 (22 to 28) μm, J (hyaline portion of tail) 6.0 ± 0.9 (5.0 to 7.5) μm, body diameter at beginning of J 8.5 ± 1.0 (7.5 to 10.5) μm, body diameter at 5 μm from tail terminus 7.5 ± 0.2 (7.0 to 8.0) μm, and V% 52.2 ± 1.8 (49.4 to 55.0) μm. Molecular diagnosis of X. rivesi was confirmed after DNA was extracted from two individual nematodes by mechanical disruption with a micro knife in 20 μl worm lysis buffer containing 500 mM KCl, 100 mM Tris-Cl (pH8.3), 15 mM MgCl2, 10 mM dithiothreitol (DTT), 4.5% Tween 20, and 0.1% gelatin. DNA extracts were stored at –80°C until needed, then thawed, 1 μl proteinase K (from 2 mg/ml stock) was added, and the tubes were incubated at 60°C for 60 min, followed by 95°C for 15 min. The 28S large ribosomal D2-D3 expansion segment was amplified with D2A (5′-ACAAGTACCGTGAGGGAAAGTT-3′) and D3B (5′-TCGGAAGGAACCAGCTACTA-3′), and the internal transcribed spacer (ITS) region was amplified with primers TW81 (5′-GTTTCCGTAGGTGAACCTGC-3′) and AB28 (5′-ATATGCTTAAGTTCAGCGGGT-3′), as previously described (3). To verify the identity of the sequences generated from PCR, sequenced products were subjected to a database search using BLAST. Sequences from the 28S region were >99% identical to several sequences of X. rivesi sampled from Spain (GenBank Accessions JQ990038, JQ990039, HM921357, and HM921358). Sequences from the ITS region were 97 to 98% identical to X. rivesi sequences (FR878063 to FR878066) obtained from the host Vitis vinifera from Italy. To the best of our knowledge, this is the first report of this nematode from the Washington. The quick and persistent spread of CRLV in most of the orchards visited calls for concern and there is need for urgent control measures against this vector nematode. References: (1) W. R. Jenkins. Plant Dis. Rep. 48:692, 1964. (2) S. Sirca et al. Plant Dis. 91:770, 2007. (3) Skantar et al. J. Nematol. 44:58, 2012. (4) M. R. Wojtowicz. et al. J. Nematol. 14:511, 1982.

Purpose– In disaster risk reduction (DRR), it is important to realise stakeholders’ approaches against disasters in the built environment. The purpose of this paper is to explore why stakeholders take proactive and/or reactive approaches in DRR.Design/methodology/approach– Using a review of existent literature, this work scrutinises disaster theories and their applications in the built environment to develop a theoretical framework for perceiving stakeholders’ proactive and/or reactive approaches in DRR.Findings– Stakeholders’ organisational attributes – power, legitimacy and urgency – and decision-making paradigms – value maximisation and intuitive reasoning – are fundamental factors affecting stakeholders’ approaches against disasters. Power and legitimacy of stakeholders result in a proactive approach if stakeholders consider value maximisation paradigm in their decision-making process. Powerful and legitimate stakeholders may take reactive approaches because of intuitive reasoning paradigm. Stakeholders may shift from a reactive to proactive approach and vice versa based on the combination of urgency attribute and decision-making paradigms.Research limitations/implications– It is essential to consider the classification of respective stakeholders in applying the idea of this paper. Furthermore, this paper does not attempt to validate the proposed theoretical framework empirically, but it combines stakeholder and decision-making theories by which this could be undertaken.Originality/value– Little attention has been paid to systematic theorising in managing stakeholders’ approaches against disasters. Furthermore, many researchers have focused on similar underlying theories and heuristics in the context of DRR. Thus, this paper introduces a theoretical framework to examine stakeholders’ proactive and/or reactive approaches in the built environment, by synthesising stakeholder and decision-making theories.

Resistance to Columbia Root-knot nematode was discovered in three wild species in a polyploidy series, Solanum bulbocastanum (2n = 2x), .S. fendleri (2n = 4x), and S. hougasii, 2n = 6x, respectively. After several generations of introgression into the cultivated gene pool, a single dominant monogene conditioning resistance to root propagation of race 1 of CRKN was theorized to be acting in breeding lines derived from each species. Coincidently, sequence tagged sites (STS) and cleaved amplified polymorphic site (CAPS) markers that associated with resistance with S. bulbocastanum were found to be informative in other segregating breeding populations regardless of the source of the gene. The utility of the markers across ploidies suggests that the original gene and genome of S. bulbocastanum or a modern derivative, is present in S. fendleri and S. hougasii. In this polyploidy series, knowledge that the S. bulbocastanum genome is the original source of useful genes guides future germplasm surveyors to search first and most intensively in the primitive Mexican diploid species that may have served as the contributor of a genome to descendants harboring this genome at higher ploidies.

Bridges are principal and vital transportation structures. If risk management is not considered in bridge construction projects, objectives cannot be delivered on time, on budget, or with suitable quality results. Risk data set sizes and experts’ judgments are not usually sufficient for analyzing significant risks in bridge construction projects; moreover, the statistical distributions for risk parameter estimates are usually unknown. Standard parametric statistical techniques cannot provide appropriate solutions for cases with small data sets or unknown distributions. This paper proposes a new hybrid approach by using a nonparametric resampling technique and interval computations for risk analysis, in particular, for bridge construction projects. Bootstrap techniques produce more accurate inferences for comparing parametric techniques and are an alternative when the underlying parametric assumptions are not considered. Increasingly, because of the complexity and uncertainty in decision making at bridge projects, it is easier or more natural to provide interval values for parts or all of decision-making judgments. Furthermore, the goal of reducing standard deviations for both risk probability and risk impact compared with the conventional approach is another conclusion of this paper. The proposed approach is applied to a case in Iran to show the validity of the approach.

The identification and assessment of project risks among potential risks can be considered a multi-attribute group decision making (MAGDM) problem including both quantitative and qualitative criteria. We extend the concept of safety to risk identification and assessment; this is to emphasize that the focus should not only be on the time and cost criteria, but also on the health, safety and environment (HSE) criterion. Conventional approaches to risk identification and risk assessment separately tend to be less effective in dealing with the imprecise of the risk assessment individually. The aim of this paper is to present a new methodology for identifying and assessing risks simultaneously by applying MAGDM technique. This paper includes a new procedure for classifying potential risks which it is named potential risk breakdown structure (PRBS) based on project work breakdown structure (WBS). Nominal group technique (NGT) is utilized for gathering potential risks. Obtained results have been applied in gas refinery plant construction successfully.

Project risk management process can remarkably facilitate project’s complexity via strategic insight. In project risk management, the modelling process of the risks may not be performed sufficientl...

Resistance to Meloidogyne chitwoodi was introgressed from Solanum bulbocastanum into the cultivated gene pool of potato. A single dominant gene is responsible for resistance to race 1 reproduction on the root system. An additional form of resistance was discovered in certain advanced backcross clones. A BC5 clone, PA99N82-4, resisted invasion of tubers by available nematode juveniles whether supplied by weeds or challenged by several root resistance-breaking pathotypes. This tuber resistance is inherited as a single dominant gene and is linked to RMc1(blb). Because this gene has been mapped to chromosome 11, tuber resistance genetic factors are inferred to be on the same chromosome in coupling phase. Among 153 progeny derived from crosses with PA99N82-4, 42 recombinants, comprising both resistant root/susceptible tuber and susceptible root/resistant tubers, were found while other progeny were doubly resistant (like PA99N82-4) or doubly susceptible. Therefore, the existence of two linked genetic factors controlling independently expressed traits is confirmed. The combination of the two phenotypes is likely to be a sufficient level of resistance to avoid tuber damage from circumstances that provide exogenous juveniles proximal to the tubers in the soil. These factors are weed hosts of M. chitwoodi host races and pathotypes of M. chitwoodi that overcome RMc1(blb). Under field conditions, where a resistance-breaking pathotype of M. chitwoodi was present, tuber-resistant PA99N82-4 breeding line produced tubers which were commercially acceptable and not culled. A related breeding line, root resistant but tuber susceptible, and Russet Burbank were severely tuber damaged and commercially unacceptable.

Corky ringspot disease (spraing) is incited by the tobacco rattle virus (TRV) transmitted by stubby root nematode (Paratrichodorus spp.). The resulting damage consists of internal and skin surface necrotic blemishes which render the tubers unmarketable. Resistance to the disease has been extensively documented in breeding programs. High levels of resistance are known for a number of varieties and breeding lines. Because tubers that are symptomless but virus infected have been documented, the nature of resistance is a point of debate. In two field locations where a total of 1,259 tubers of resistant breeding lines were RT-PCR tested, 5.6 and 2.0% of symptomless tubers gave positive PCR tests in the different fields. Nearly all of these were from three clones that would have been classified as susceptible by symptoms in later testing. Taken as a whole 58% of the symptomatic tubers gave positive PCR tests. Standard commercial susceptible cultivars showed 34% symptomless tubers with positive PCR results. We have shown here that tubers of most resistant lines are not positive for the virus when asymptomatic tubers are tested by RT-PCR, while symptomatic tubers are mostly positive. Within selected resistant materials, clones with the highest level of asymptomatic positives also showed susceptible responses as assessed by visual ranking in later tests. Although RT-PCR fails to amplify from symptomatic tubers in some cases, the results of this study suggest that most resistant breeding lines do not test positive as latent carriers of the virus. Therefore, lack of symptoms appears to be an expression of resistance to infection by TRV.

Hairy nightshade is a common weed in potato rotations in the western United States. As a close relative of potato, hairy nightshade can host numerous potato nematodes, diseases, and insect pests. Hairy nightshade hosts three common parasitic nematodes of potato, Columbia and northern root-knot nematodes, and stubby root nematode. Tubers of a potato breeding line with roots that are resistant to Columbia root-knot nematode—race 1, were damaged when grown in the presence of hairy nightshade. The weed provided an alternate host for the nematode, which then allowed the nematode to infect susceptible tubers. Stubby root nematodes transmit tobacco rattle virus (TRV), the causal agent for corky ringspot disease (CRS) of potato. CRS disease was maintained in soil when hairy nightshade was present in rotation crops of alfalfa or Scotch spearmint that otherwise eliminated the disease. Hairy nightshade also is a host of potato leaf roll virus (PLRV), which is transmitted by green peach aphids (GPA). GPA pre...

Columbia root-knot nematode, Meloidogyne chitwoodi, is a major pest of potato in the Pacific Northwest of the USA and is controlled by costly soil fumigation. Potato breeding lines have been developed with resistance to the predominant race 1 (CRKN-1) of M. chitwoodi. Hairy nightshade, Solanum sarrachoides, is a common weed in potato production in the western USA and a host of CRKN-1. Greenhouse and field studies were conducted with two potato lines with known CRKN-1 resistance (PA95B4-67 and PA99N82-4) and a CRKN-1 susceptible potato cultivar, Russet Burbank. Very little or no CRKN-1 reproduction took place in roots of both resistant breeding lines, and only minor tuber infection occurred when grown in the absence of hairy nightshade. However, when resistant lines were grown in the presence of hairy nightshade, some PA95B4-67 tubers were infected, whereas PA99N82-4 expressed tuber resistance. Hairy nightshade grown with potato maintained CRKN-1 populations prior to potato tuber set, allowing nematodes to infect developing tubers lacking resistance. PA99N82-4 grown in the presence of CRKN-1 and hairy nightshade produced tubers free of CRKN-1 damage, indicating both root and tuber resistance to CRKN-1. Russet Burbank tubers were damaged by CRKN-1 regardless of hairy nightshade presence. These results demonstrate how weed hosts of CRKN-1 may negate the positive impact of growing CRKN-1 resistant potatoes that lack tuber resistance, and the importance of weed control on managing plant parasitic nematode populations.

Columbia root-knot nematode (Meloidogyne chitwoodi) (CRN) is a serious pest of potato in the Pacific Northwest of the USA. Because this nematode can reproduce rapidly within a single growing season, small initial populations are capable of causing crop loss in the Columbia Basin of Washington or Oregon. Presently, soil fumigation is the main treatment for controlling CRN on potato. Developing potato varieties with resistance to CRN is highly desirable to reduce the cost of control and to alleviate concerns about the effects of fumigants on the environment. Resistance to CRN race 1 was found in two wildSolanum species. Resistance fromS. bulbocastanum was introduced via protoplast fusion and fromS. hougasii via sexual hybridization. Subsequent breeding consisted of repeated backcrossing and selection. The dominant monogenic inheritance was expressed in undiminished fashion across several backcross generations. When tested in replicated trials in three locations, selected resistant clones from the BC4 and BC5 of theS. bulbocastanum introgression populations had total marketable yields and yields of >113-g (4 oz) tubers as good or better than standard potato varieties tested in replicated yield trials in three locations. Percentage of tubers weighing more than 113 g in the highest yielding clones was not significantly different from commercial standards. The resistance phenotype, typified by failure of the nematode to reproduce on the root systems, was sufficiently effective to prevent economic damage in a field exposure. All CRN-resistant clones are pollen sterile. Germplasm listed is available upon request.

Twelve accessions ofSolarium fendleri collected in the United States and Mexico were inoculated with 5,000 eggs of host-races 1 and 2 ofMeloidogyne chitwoodi, Columbia root-knot nematode. The test seedlings that were derived from plant introduction true seed lots were maintained for 55 days before harvest and egg count. The results revealed that two accessions, PI 275162 and PI 275165, were non-hosts (final egg count/initial egg inoculation < 0.1) forM. chitwoodi race 1. The results were uniformly confirmed in the second experiment. No resistance was found to race 2. The tetraploidS. fendleri accessions were crossed to a nematode-susceptible cultivated diploid potato clone from aS. phurejastenotomum population. The triploid hybrids expressed resistance to race 1 at the non-host level. After somatic doubling, the resulting hexaploids also expressed non-host-level resistance to race 1. The two resistant accessions had been collected in southeastern Arizona, one each from the Huachuca and Chiricahua Mountains. Each range is an isolated island of high-elevation mesic flora surrounded by typical lowerelevation Sonora-type desert habitat. These accessions are the only known sources of resistance toM. chitwoodi from wildSolanum species in the USA.

Corky ringspot disease (CRS) of potato is caused by tobacco rattle virus (TRV). The virus is transmitted by the stubby root nematode (Paratrichodorus allius) in the Pacific Northwest potato-producing regions. Alfalfa (Medicago sativa L.) and Scotch spearmint (Mentha cardiaca Baker) rarely serve as hosts for TRV. Therefore,P. allius reared on these plants for 1 to 3 months are cleansed of TRV in greenhouse trials. However, weeds in alfalfa and Scotch spearmint rotation crops may serve as hosts for the virus. In greenhouse trials, hairy nightshade (Solanum sarrachoides), prickly lettuce (Lactuca serriola), henbit (Lamium amplexicaule) and, green foxtail (Setaria viridis) grown alone were found to be suitable hosts ofP. allius, whereas Powell amaranth (Amaranthus powellii) was not. ViruliferousP. allius added to hairy nightshade, prickly lettuce, henbit, green foxtail, or Powell amaranth in mixtures with alfalfa and/or Scotch spearmint occasionally remained viruliferous over a 3-to 4-month period, whereasP. allius maintained on weed-free alfalfa or Scotch spearmint became virus-free after 1 to 2 months. Potato grown in soil containingP. allius that had been maintained on weed-alfalfa or weed-Scotch spearmint mixtures for 3 to 4 months exhibited slight to severe CRS symptoms on new tubers, whereas potato following weed-free Scotch spearmint or alfalfa were free from CRS symptoms. Severe CRS symptoms on potato tubers were only observed when potatoes were grown in soil containingP. allius that were maintained on hairy nightshade or hairy nightshade mixtures with alfalfa or Scotch spearmint. These preliminary data suggest that the presence of weeds that serve as hosts of both TRV and P.allius may nullify the positive effects of growing alfalfa or Scotch spearmint for CRS control. Targeted control efforts of known weed hosts may be required to successfully eliminate CRS from fields using alfalfa and Scotch spearmint rotational crops.

The ability of several weed species to serve as hosts for tobacco rattle virus (TKV), the causal agent of corky ringspot disease of potato (CRS), and its nematode vector,Paratrichodorus allius, was investigated in greenhouse studies. ViruliferousP. allius multiplied on 24 out of 37 weed species tested, indicating they were suitable hosts of the vector. However, only 11 of these weeds were infected with TRV, as determined by ELISA. The nonhost status of a given weed species was not changed whether the viruliferous vector population originated from CRS problem fields in WA, OR, or ID. Several weeds served as hosts for the vector and virus including kochia, prickly lettuce, henbit, nightshade species (black, hairy, and cutleaf), common chickweed, and annual sowthistle. Virus-freeP. allius acquired TRV from the three nightshade species, volunteer potato grown from TRV-infected tubers, and prickly lettuce, and subsequently transmitted the virus to ‘Samsun NN’ tobacco indicator plants. Thus, some weeds may play a role in the epidemiology of CRS by perpetuating TRV and its vector in a problem field.

Tobacco rattle virus (TRV), the causal agent of corky ringspot disease of potato (CRS), was detected by reverse transcription-polymerase chain reaction (RT-PCR) in root tissues of field- and greenhouse-grown wheat (two) and corn (10) cultivars. TRV was also detected in some of the same samples by enzyme-linked immunosorbent assay (ELISA), but in a low frequency. Compared to ‘Samsun NN’ tobacco, wheat and corn appeared to be poorer hosts of TRV. However, these crops served as inoculum reservoirs of TRV. A nonviruliferous population of the nematodeParatrichodorus allius, the vector of TRV, acquired the virus from infected wheat and corn roots, and transmitted it to potato. ‘Russet Norkotah’ potatoes grown following TRV-infected corn and wheat, were blemished with arcs, concentric rings and diffuse browning, characteristic symptoms of CRS. The observations presented here suggest that wheat and corn as rotational crops will sustain TRV in a CRS problem field and the virus may cause severe damage on subsequent potato crops.

Soil samples from corky ringspot (CRS) problem fields of potato in the states of Washington and Oregon were collected and planted withNicotiana tabacum ‘Samsun NN’ tobacco to bait tobacco rattle virus (TRV) and to increaseParatrichodorus allius populations, the vector of TRV. Pathogenicity of three isolates of TRV was assessed on Russet Burbank and Russet Norkotah plants usingP. allius as the vector. The most severe CRS tuber symptoms were with TRV from Pasco, WA, followed by Umatilla, OR, and Mattawa, WA, indicating a distinct variation in virulence among virus isolates. The lowest number ofP. allius that transmitted TRV resulting in CRS symptoms on Russet Norkotah was three nematodes per 250 cm3 soil. When potato plants were exposed toP. allius at different times in their growth, tubers on older plants were more resistant than younger tubers to CRS. Severity of CRS tuber symptoms was correlated with age of potato plants in pot culture. Reproduction ofP. allius on potato roots did not influence the incidence and severity of tubers symptoms. Under similar conditions, Bintje, a variety known to be resistant to CRS, served as a host forP. allius, yet remained asymptomatic. The protocol employed in these studies is appropriate for testing potato germplasm for resistance to CRS.

Potato germplasm was assessed for resistance to corky ringspot disease (CRS) incited by transmission of tobacco rattle virus (TRV). TRV is transmitted by the stubby root nematode,Paratrichodorus allius, in the Pacific Northwest, and characterized by necrotic areas in the tuber. Four tests were conducted at two different problem fields in Umatilla, OR and Pasco, WA. The fields differed in the virulence of the virus isolates. Some clones and named varieties showed resistance only in the field with the relatively mild Umatilla isolate, while others remained symptomless at both sites. The host suitability of test potatoes to threeP. allius populations from the region was determined in greenhouse pot tests, and expressed as reproductive values [Rf = (final population of nematode at 55 days) / (initial population)]. TheR f values for the nematodes were not correlated with resistance ratings based on visual scoring of CRS symptoms in field grown potatoes. Thus, it appears that CRS resistance is based on reaction of potato genotypes to virus and not the vector. The availability of resistant clones inin vitro form is indicated.

Paratrichodorus allius, a vector of the tobacco rattle virus which causes the corky ringspot disease (CRS) in potato, was identified in soil samples from Oregon and Washington. Two populations from potato fields in Pasco, WA and Umatilla, OR reproduced successfully on alfalfa, wheat, and corn which are commonly rotated with potato, and most weeds associated with this crop in the Pacific Northwest. Greenhouse studies showed thatP. allius was sensitive to low soil moisture, and increased 10 and 100 fold on Samsun NN tobacco in soil above field capacity compared to 1/2 and 1/3 field capacity, respectively. Population dynamic studies for 1996 and 1997 on a potato-wheat cropping sequence showed thatP. allius declined after the winter wheat cover crop was disked in the spring of 1996, and remained low on potato at the 0–90 cm soil profile, with no evidence of downward migration. In 1997,P. allius declined early in the season on wheat, and remained low until June–July when it peaked before declining again. In soil columns,P. allius placed 30 cm below a confined tobacco root system was able to reach and transmit tobacco rattle virus. The nematodes below 30 cm transmitted the virus only when plant roots were allowed to grow to that depth.

Milkweed (Asclepias) is a new crop being produced for its fiber in pillows and comforters. Cardiac glycosides (cardenolides), are endemic in milkweed and may hinder utilization of its seed as an animal feed. In an ongoing effort to develop new coproducts for milkweed fiber, we found that the defatted seedmeal is an effective nematicide and pesticide for army worms. A procedure for separating the cardenolides from milkweed seedmeal has also been developed.

Sicklepod ( Cassia obtusifolia ) is a leguminous weed species that has become a severe problem in soybean production throughout the Southern United States. Economic incentives, such as premiums for low levels of foreign matter from cleaning soybeans prior to sale, could generate a large source of sicklepod seed in that area. This study was undertaken to evaluate C. obtusifolia seed for potential applications. As much as 41% of the seed was extractable. Some extracts were strong inhibitors of wheat, velvetleaf and sicklepod root growth, causing discoloration of the root meristems in a manner similar to that caused by naphthoquinones such as juglone and plumbagin. Some extracts increased weight gain in fall armyworm ( Spodoptera frugiperda ) causing them to grow to 50–100% larger than controls in a 7-day trial. Survival of Columbia root-knot nematode ( Meloidogyne chitwoodi ) in the soil was inversely correlated to the amount of ground whole sicklepod amendment. No phytotoxic effects of the meal amendment on tomato plants or inhibition of germination for several crop seeds was observed at the levels tested.

Resistance toMeliodogyne chitwoodi races 1 (MC1) and 2 (MC2) andM. hapla (MH) derived fromSolanum bulbocastanum was introduced into the cultivated potato gene pool through somatic fusion. The initial F1 hybrids showed resistance to the three nematodes. Resistance to reproduction on roots by MC1 was accompanied by resistance to tuber damage in F1 clones. Tuber damage sometimes occurred, however, in hybrids of BC1 progeny resistant to reproduction on roots when MC2 and MH were the challenging nematodes. Resistance to reproduction was transferred into BC1 individuals, but a greater proportion of BC1 progeny was resistant to MC1 than to MC2 or MH. Resistance to MC1 appears to be dominant and discretely inherited. F1 and BC1 progeny were pollen sterile, but seed were produced from crosses using cultivated tetraploid pollen sources. Approximately 11 and 33 per cent of pollinations produced berries on F1 and BC1 pistillate parents, respectively. Seed yield increased fourfold overall in crosses with F1 compared to BC1 individuals.

Interspecific somatic hybrids were produced between tetraploid Solanum tuberosum and a nematode-resistant accession of the diploid species So/ahum bulbocastanum by protoplast fusion. Hybrid cells were selected using dual fluorescent labeling of protoplast preparations prior to fusion. Hybridity of regenerated plants was confirmed with a combination of morphological assessment, chromosome counting and isozyme analysis. Somatic hybrids had the same level of resistance to infection by race 1 of the nematode Meloidogyr~ chitwoodi as the S. bulbocastanum parent used in the fusion. Some of the somatic hybrids were fertile as females when crossed with tetraploid S. tuberosum breeding lines. Thus, these hybrids can be used in a potato improvement program to incorporate a valuable pest resistance.

Fertilizer which generated NH₃ was detrimental to Criconemoides xenoplax grown in the greenhouse. The fertilizer was lethal to the nematodes in vitro only when it was accompanied by urease-positive bacteria or partially purified urease. The detrimental action of the fertilizer-urease mixture was ntore rapitt at pH 8 than at pH 7.

Most of the 15 carrot cultivars tested were moderate to good hosts to Meloidogyne chitwoodi race 1, whereas all except Orlando Gold were nonhosts or poor hosts for M. chitwoodi race 2. All carrot cultivars were good hosts for M. hapla. The plant weights of the carrot cultivars Red Cored Chantenay and Orlando Gold infected with either race of M. chitwoodi were significantly less than uninoculated checks in pots. Under field microplot conditions, however, detrimental effects on quality were rarely observed. M. hapla was pathogenic to both cultivars in the greenhouse and the field. The tolerance level of Orlando Gold to M. hapla was lower than Red Cored Chantenay.

Second-stage juveniles (J2) of races 1 and 2 of Meloidogyne chiiwoodi and M. hapla readily penetrated roots of Thor alfalfa and Columbian tomato seedlings; however, few individuals of M. chitwoodi race 1 were able to establish feeding sites and mature on alfalfa. Histopathological studies indicate that J2 of race 1 either failed to initiate feeding sites or they caused cell enlargement without typical cell wall thickening. The protoplasm of these cells coagulated, and juveniles of race 1 did not develop beyond the swollen J2 stage. A few females of race 1 fed on small giant cells and deposited a few eggs at least 20 and 30 days later than M. chitwoodi race 2 and M. hapla, respectively. Failure of race 1 to establish feeding sites was related to egression of J2 from the roots. The M. chitwoodi race 1 J2 egression from alfalfa roots was higher than egression of race 2 and M. hapla. Egression of J2 of M. chitwoodi races 1 and 2 from tomato roots was similar and higher than that of M. hapla. Thus egression plays an important role in the host-parasite relationship of M. chitwoodi and alfalfa.

Migratory ability of second-stage juveniles (J2) of two Meloidogyne chitwoodi races and a M. hapla population were compared in soil-filled columns at 12, 18, and 24 C. J2 of all populations migrated farthest at 18 C and least at 12 C. Nematode survival was significantly reduced (P = 0.05) at 24 C.M. chitwoodi J2 migrated further and in greater numbers than M. hapla J2 at all temperatures. A comparison with and without a host plant demonstrated no preferential migration toward the plant. Water percolation through the migration columns stimulated upward migration.

Meloidogyne chitwoodi races 1 and 2 and M. hapla reproduced on 12 cultivars of Brassica napus and two cultivars of B. campestris. The mean reproductive factors (Rf), Rf = Pf at 55 days ÷ 5,000, for the three nematodes were 8.3, 2.2, and 14.3, respectively. All three nematodes reproduced more efficiently (P < 0.05) on B. campestris than on B. napus. Amending M. chitwoodi-infested soil in plastic bags with chopped shoots of Jupiter rapeseed reduced the nematode population more (P < 0.05) than amendment with wheat shoots. Incorporating Jupiter shoots to soil heavily infested with M. chitwoodi in microplots reduced the nematode population more (P < 0.05) than fallow or corn shoot treatments. The greatest reduction in nematode population density was attained by cropping rapeseed for 2 months and incorporating it into the soil as a green manure.

Seasonal vertical migration of Meloidogyne chitwoodi through soil and its impact on potato production in Washington and Oregon was studied. Nematode eggs and second-stage juveniles (J2) were placed at various depths (0-180 cm) in tubes filled with soil and buried vertically or in holes dug in potato fields. Tubes were removed at intervals over a 12-month period and soil was bioassayed on tomato roots. Upward migration began in the spring after water had percolated through the tubes. Nematodes were detected in the top 5 cm of tubes within 1-2 months of burial, depending on depth of placement. Potatoes were grown in field plots for 4 or 5 months before the tubers were evaluated for infection. One hundred eggs and J2 per gram soil placed at 60 and 90 cm caused significant tuber damage at the Washington and Oregon sites, respectively. At the Washington site, inoculum placed at 90, 120, and 150 cm caused potato root infection without serious impact on tuber quality, but inoculum diluted 2-8 times and placed at 90 cm did not cause root or tuber infection. Nematode migration was dependent on soil texture; 9 days after placement at the bottoms of tubes, J2 had moved up 55 cm in sandy loam soil (Oregon) but only 15 cm in silt loam (Washington). Thus, the importance of M. chitwoodi which occur deep in a soil profile may depend on soil texture, population density, and length of the growing season.

Responses of egg masses, free eggs, and second-stage juveniles (J2) ofMeloidogyne hapla and M. chitwoodi to ethoprop were evaluated. The results indicated that J2 were the most sensitive, followed by free eggs and egg masses. In general, M. chitwoodi was more susceptible to ethoprop than M. hapla. Ethoprop at 7.2 mug a.i./g soil protected tomato roots from upward migrating M. chitwoodi for 5 weeks. The zone of protection was extended to 10 and 20 cm below the root zone when 3.6 and 7.2 cm water were applied over 8 days. Ethoprop at 1.8, 3.6, and 7.2 mug a.i./g soil degraded faster and killed fewer M. chitwoodi J2 in potato field soil previously exposed to ethoprop than in unexposed soil or sterilized exposed soil. The enhanced biodegradation property of the exposed soil lasted 17 months after the last application of ethoprop. The limited downward movement of ethoprop in the soil, migration of M. chitwoodi J2 into the treated zone, presence of resistant life stage(s) at the time of application, and loss of efficacy due to enhanced biodegradation may have a significant effect on the performance of ethoprop.

An accession of Solanum hougasii, a wild tuber-bearing potato species native to Mexico, was found to be resistant to races 1 and 2 of Meloidogyne chitwoodi. A resistant selection was selfed and its progeny possessed the same combined resistance uniformly. A selected resistant seedling from the selfed progeny was crossed to cultivated tetraploid potato (S. tuberosum) to form an F₁ hybrid, and was backcrossed to cultivated tetraploid potato to form a BC₁ population in which resistance to the two races segregated. Progeny of the BC₁ were tested in inoculation experiments with four replicates for each progeny genotype for each race of nematode. Resistance was evaluated on the basis of extracted egg counts from the entire root system of pot-grown plants. Considering resistance to each race separately, for race 1, non-host (Rf ≤ 0.1) status was exhibited by approximately half of the BC₁. About one-third of the progeny showed non-host status to race 2. Egg production among progeny that showed non-host status for both races was higher with race 2 than with race 1. Analysis of co-segregation established that genetic control for the two races appears to be independently segregating. Although genes for resistance to race 1 derived from S. bulbocastanum and S. fendleri were previously described, this report is the first analysis showing independent genetic control in Solanum spp. for resistance to race 2 of M. chitwoodi only.

Several tuber-bearingSolanum species were screened for resistance to races 1 and 2 of Columbia root-knot nematode,Meloidogyne chitwoodi. Reproductive factor (Rf = Pf/Pi) was assessed and used to infer host resistance. Several clonal selections in one Plant Introduction accession ofSolanum hougasii showed high levels of resistance to both races. Crosses ofS. hougasii with tetraploid breeding clones yielded 14 vigorous F1 hybrids. Three of these interspecific hybrids expressed non-host (Rf 1.0) to race 2. Three hybrids were good hosts to both races, and one was a poor host to race 1 and non-host to race 2. The occurrence of resistance to both races in the F1 hybrids indicates success in the first step of introducing resistance to races 1 and 2 ofM. chitwoodi to the cultivated potato gene pool.

A method to establish two experimental corky ringspot disease (CRS) plots that had no prior CRS history is described. CRS is a serious disease of potato in the Pacific Northwest caused by tobacco rattle virus (TRV) and transmitted primarily by Paratrichodorus allius. ‘Samsun NN’ tobacco seedlings were inoculated with viruliferous P. allius in the greenhouse before they were transplanted into the field soil at the rate of 3,000 plus seedlings/ha. Care was taken to keep soil around plants in the greenhouse and transplants in the field moist to avoid vector mortality. The vector population in the soil of one of the fields was monitored by extraction, examination under microscope and bioassay on tobacco seedlings to ascertain that they were virus carriers. Presence of virus in tobacco bioassay plants was determined by visual symptoms on tobacco leaves and by testing leaves and roots using ELISA. Although TRV transmission was rapid, there was loss of infectivity in the first winter which necessitated a re-inoculation. After two years of planting infected tobacco seedlings, 100% of soil samples collected from this field contained viruliferous P. allius. In the second field, all five commercial potato cultivars, known to be susceptible, expressed symptoms of CRS disease indicating that the procedure was successful.

Several malignancies over-express the epidermal growth factor receptor, ligation of which results in cellular differentiation and multiplication. Mononuclear phagocytes secrete this cytokine and its receptor has been detected on microglial cells. This communication describes the expression (and its regulation) of epidermal growth factor receptor (EGFR) on U937 cells. We have shown that a few are EGFR-positive, with expression being up regulated by interleukin 6 (IL-6). Also, when cultured in the presence of serum with the monoclonal anti-EGFR, ICR62, U937s showed a reduced growth rate. By contrast, ICR9 caused a significant increase in cellular proliferation. Both antibodies induced cycle arrest in late G(1)/S phase. When the cells were cultured in the absence of serum, low antibody concentration (10 microg/ml) showed an early inhibitory effect on cell proliferation. By contrast, at high antibody concentrations (50 micro/ml), ICR62 significantly increased the proliferation of U937 cells. We suggest that these results provide indirect evidence for an autocrine action of EGF on U937 cells.

The mapping of resistance toMeloidogyne chitwoodi derived from Solarium bulbocastanum is reported. A population suitable for mapping was developed as follows. A somatic hybrid of nematode-resistant S. bulbocastanum and cultivated tetraploid potato was produced. This was backcrossed to tetraploid potato, and a single resistant BC1 was selected and backcrossed again to the same recurrent tetraploid parent. The mapping population consisted of 64 BC2 progeny scored for restriction fragment length polymorphic (RFLP) markers and 62 of these were evaluated for the reproductive efficiency of race 1 of M. chitwoodi. Forty-eight polymorphic RFLP markers, originally derived from tomato and mapped in diploid cultivated potato, were assigned to 12 chromosomes of S. bulbocastanum. Of the 62 progeny screened for nematode resistance, 18 were non-hosts and four were poor hosts. The rest were highly susceptible (good hosts). Analysis of the resistance (including non-hosts and poor hosts) as both a qualitative trait and as a meristic trait on which QTL analysis was applied supported the same genetic hypothesis. Genetic control was localized solely to factor(s) lying at one end of chromosome 11. The level of expression of resistance in the S. bulbocastanum parent and the resistant portion of the BC2 was essentially the same. This fact, together with the highly significant LOD scores for one end of the chromosome-11 marker array, supports a genetic model equivalent to monogenic dominant control.

The potato cyst nematode, Globodera pallida (PCN), a restricted pest in the United States, was first reported in Bingham and Bonneville counties of Idaho in 2006 (1). The U.S. government and Idaho State Department of Agriculture hope to eradicate it from infested fields. Eradicating PCN will require depriving the nematodes of their hosts over a protracted time period. Functional eradication might be achieved with relatively high, proven to be efficacious dosages of soil fumigants. The presence of host weeds of PCN can play a significant role in the success of the eradication program. To determine the host status of common weeds found in potato fields of the Pacific Northwest, host suitability tests were conducted in a secured greenhouse located at the University of Idaho at Moscow. Reproduction of PCN on nine weeds including hairy nightshade (Solanum physalifolium formerly S. sarrachoides) and cutleaf nightshade (S. triflorum) (biotypes from Idaho and Washington), black nightshade (S. nigrum) (Washington biotype), bittersweet nightshade (S. dulcamara) (Idaho biotype), redroot pigweed (Amaranthus retroflexus), kochia (Kochia scoparia), and common lambsquarters (Chenopodium album) were compared with reproduction on Desiree, Russet Burbank (known hosts), and Santé (poor host) potatoes (S. tuberosum). Plants were grown in 10-cm-diameter clay pots containing sandy loam soil previously fumigated with methyl bromide and inoculated with 10 to 150 cysts that were either collected from infested fields or raised in the secured greenhouse (ample diapause period elapsed). Treatments were replicated five times and each trial lasted 3 months. Cysts were extracted from soil with a Fenwick can, and the reproductive factor (RF = final cyst count ÷ initial inoculum) was determined. While both biotypes of hairy nightshade were suitable hosts of PCN (161–668 ÷ 150; RF = >1), cutleaf biotypes, black, and bittersweet nightshades were poor hosts (1–108 ÷ 150; RF = 1) proved to be suitable hosts and Santé (1–20 ÷ 150; RF = Reference: (1) A. M. Skantar et al. J. Nematol. 39:133, 2007.