Developing a Real-Time PCR Assay for Direct Identification and Quantification of Soybean Cyst Nematode, Heterodera glycines, in Soil and Its Discrimination from Sugar Beet Cyst Nematode, Heterodera schachtii

The soybean cyst nematode (SCN) Heterodera glycines continues to be a major threat to soybean production worldwide. Morphological discrimination between SCN and other nematodes of the Heterodera schachtii sensu stricto group is not only difficult and time-consuming but also requires high expertise in nematode taxonomy. Molecular assays were developed to differentiate SCN from sugar beet cyst nematode (SBCN) and other nematodes and to quantify SCN directly from DNA extracts of field soils. SCN- and SBCN-specific quantitative real-time PCR (qPCR) primers were designed from a nematode-secreted CLAVATA gene and used for these assays. The primers were evaluated on the basis of target specificity to SCN or SBCN using DNA from 20 isolates of SCN and 32 isolates of other plant-parasitic nematodes. A standard curve relating threshold cycle and log values of nematode numbers was generated from artificially infested soils and was used to quantify SCN in naturally infested field soils. There was a high correlation between the SCN numbers estimated from naturally infested field soils by conventional methods, and the numbers quantified using the SYBR Green I-based qPCR assay. The qPCR assay is highly specific and sensitive and provides improved SCN detection sensitivity down to 1 SCN egg in 20 g of soil (10 eggs/200 g soil). This assay is useful for efficient detection and quantification of SCN directly from field soil. Species-specific conventional PCR assays were also developed each for SCN and SBCN, alongside a qPCR assay that simultaneously discriminates SCN from SBCN. These assays require no expertise in nematode taxonomy and morphology, and they may serve as useful diagnostic tools in research, diagnostic laboratories, and extension services for SCN management. Sensitive and accurate detection and quantification of SCN are essential for recommending effective management measures against SCN. We also investigated the impact of soil texture and nematode life stage on molecular quantification of SCN.

Characterization of Virulence Phenotypes of Soybean Cyst Nematode (Heterodera glycines) Populations in North Dakota

Soybean cyst nematode (SCN; Heterodera glycines) continues to be the greatest threat to soybean production in the United States. Because host resistance is the primary strategy used to control SCN, knowledge of SCN virulence phenotypes (HG types) is necessary for choosing sources of resistance for SCN management. To characterize SCN virulence phenotypes in North Dakota, a total of 419 soybean fields across 22 counties were sampled during 2015, 2016, and 2017. SCN was detected in 42% of the fields sampled, and population densities in these samples ranged from 30 to 92,800 eggs and juveniles per 100 cm3 of soil. The SCN populations from some of the infested fields were virulence-phenotyped with seven soybean indicator lines and a susceptible check ('Barnes') using the HG type tests. Overall, 73 SCN field populations were successfully virulence-phenotyped. The HG types detected in North Dakota were HG types 0 (frequency rate: 36%), 7 (27%), 2.5.7 (19%), 5.7 (11%), 1.2.5.7 (4%), and 2.7 (2%). However, before this study only HG type 0 was detected in North Dakota. The designation of each of these HG types detected was also validated by repeating the HG type tests for 33 arbitrarily selected samples. This research for the first time reports several new HG types detected in North Dakota and confirms that the virulence of SCN populations is shifting and overcoming resistance, highlighting the necessity of using different resistance sources, rotating resistance sources, and identifying novel resistance sources for SCN management in North Dakota.

The Siberian pine growth dynamics in Altai Mountains, China

Climatic factors play an essential role in the growth of tree ring width. In this study, we aimed to evaluate the correlation between climatic variables and tree-ring growth characteristics of Pinus sibirica in Altai mountains, northwestern China. This study being is first of its kind on climate growth analysis of Pinus sibirica in northwestern China. The study showed great potential to understand the species growing under the specific climatic conditions. Total of 70 tree cores collected from three sites in the sampling area, out of which 63 tree cores considered for this study. The effect of climatic variables which was studied include precipitation, temperature and PDSI. Our results showed that Tree Ring Width chronology has a significantly positive correlation with the late winter (March) temperature and significant negative correlation with the July temperatures. A significant correlation was observed with the late summer precipitation whereas no significant relation found with the Palmer Drought Severity Index. These significant correlations with temperature and precipitation suggested that this tree species had the potential for the reconstruction of the past climate in the area.

[Surveillance of Enterobius vermicularis infections among children in Shandong Province from 2016 to 2020]

OBJECTIVE

To investigate the prevalence and changing trend of Enterobius vermicularis infections among children in Shandong Province, so as to provide the scientific evidence for the adjustment and development of the enterobiasis control strategy.

METHODS

Soil-borne nematodiasis surveillance sites were assigned in 51 counties (districts, cities) in Shandong Province from 2016 to 2020, and the E. vermicularis infections were detected using a modified Kato-Katz technique and the cellophane tape method among children at ages of 3 to 9 years living in these surveillance sites. The epidemiological profiles of E. vermicularis-infected children were descriptively analyzed.

RESULTS

A total of 5 060 children at ages of 3 to 9 years were detected in 51 soil-borne nematodiasis surveillance sites in Shandong Province from 2016 to 2020, and the overall prevalence of E. vermicularis infections was 2.23%. The annual prevalence of E. vermicularis infections was 3.99% (26/651), 1.70% (14/824), 0.96% (8/837), 2.90% (45/1 552) and 1.67% (20/1 196) from 2016 to 2020, respectively, with a significant difference detected among years (χ² = 21.455, P < 0.01). The prevalence of E. vermicularis infections was 1.25% (15/1 198), 1.85% (14/755), 3.18% (84/2 640) and 0 (0/467) among children from central, eastern, southern and northern Shandong Province (χ² = 27.326, P < 0.01). In addition, there was no significant difference in the prevalence of E. vermicularis infections between male (1.98%, 56/2 831) and female children (2.56%, 57/2 229) (χ² = 1.916, P > 0.05); however, there was age-specific prevalence of E. vermicularis infections among children (χ² = 16.448, P < 0.05), with the greatest prevalence detected among children at ages of 6 years (3.18%, 25/786), and the lowest prevalence seen among children at ages of 3 years (0.75%, 6/800).

CONCLUSIONS

The prevalence of E. vermicularis infections remained at a medium level among children at ages of 3 to 9 years in Shandong Province from 2016 to 2020, with region-specific prevalence found across the province. An integrated strategy is required for enterobiasis control.

Cardiometabolic index: a new tool for screening the metabolically obese normal weight phenotype

PURPOSE

People with the metabolically obese normal weight (MONW) phenotype are considered as an extremely high-risk group for unfavorable health consequences, but they are frequently undetected due to deceptive body mass index (BMI) and complex assessment. This study aimed to explore the clinical usefulness of cardiometabolic index (CMI) in identifying MONW individuals.

METHODS

This cross-sectional study involved a total of 47,683 normal-weight subjects aged ≥ 18 years. Participants underwent anthropometrics, routine biochemical tests, and questionnaires for a full evaluation of the metabolic profile. The odds ratio (OR) of CMI and MONW phenotype was determined by the Logistic regression models and the diagnostic accuracy of CMI was evaluated by the receiver operating characteristic (ROC) curve analysis.

RESULTS

The prevalence of MONW phenotype was 11.0%. After multivariate adjustment, the ORs for MONW in the highest compared with the lowest quartile of CMI was 71.20 (95% CI 55.19-91.86), and 1-SD increment of CMI brought a 54% additional risk. In ROC analysis, compared with BMI and waist circumference, CMI showed superior performance for identifying MONW individuals with an AUC of 0.853 (95% CI 0.847-0.860) in men and 0.912 (95% CI 0.906-0.918) in women, respectively. Moreover, CMI exhibited the highest diagnostic accuracy in younger age groups (aged 18-34 for men; aged 18-34 and 35-44 for women), in which AUCs surpassed 0.9 in both sexes.

CONCLUSIONS

CMI could be served as a valuable indicator to identify MONW phenotype of Chinese adults, particularly for young people.

Development of Real-Time and Conventional PCR Assays for Identifying a Newly Named Species of Root-Lesion Nematode (Pratylenchus dakotaensis) on Soybean

A rapid and accurate PCR-based method was developed in this study for detecting and identifying a new species of root-lesion nematode (Pratylenchus dakotaensis) recently discovered in a soybean field in North Dakota, USA. Species-specific primers, targeting the internal transcribed spacer region of ribosomal DNA, were designed to be used in both conventional and quantitative real-time PCR assays for identification of P.dakotaensis. The specificity of the primers was evaluated in silico analysis and laboratory PCR experiments. Results showed that only P.dakotaensis DNA was exclusively amplified in conventional and real-time PCR assays but none of the DNA from other control species were amplified. Detection sensitivity analysis revealed that the conventional PCR was able to detect an equivalent to 1/8 of the DNA of a single nematode whereas real-time PCR detected an equivalent to 1/32 of the DNA of a single nematode. According to the generated standard curve the amplification efficiency of the primers in real-time PCR was 94% with a R2 value of 0.95 between quantification cycle number and log number of P.dakotaensis. To validate the assays to distinguish P.dakotaensis from other Pratylenchus spp. commonly detected in North Dakota soybean fields, 20 soil samples collected from seven counties were tested. The PCR assays amplified the DNA of P.dakotaensis and discriminated it from other Pratylenchus spp. present in North Dakota soybean fields. This is the first report of a species-specific and rapid PCR detection method suitable for use in diagnostic and research laboratories for the detection of P.dakotaensis.

Effects of Cover Crops on Population Reduction of Soybean Cyst Nematode (Heterodera glycines)

Microplot experiments were conducted to evaluate the effects of cover crops on population reduction of a major soybean pest, soybean cyst nematode (SCN; Heterodera glycines Ichinohe) in 2016 and 2017. Ten crop species, including annual ryegrass (Lolium multiflorum L.), Austrian winter pea (Pisum sativum L. subsp. arvense), carinata (Brassica carinata A. Braun), faba bean (Vicia faba Roth), foxtail millet (Setaria italica (L.) P. Beauvois), daikon radish (Raphanus sativus L.), red clover (Trifolium pratense L.), sweetclover (Melilotus officinalis L.), turnip (Brassica rapa subsp. rapa L.), and winter rye (Secale cereale L.), were planted along with susceptible soybean (Glycine max (L.) Merr. 'Barnes') in soil naturally infested with each of two SCN populations (SCN103 and SCN2W) from two North Dakota soybean fields. Crops were grown in large plastic pots for 75 days in an outdoor environment (microplot). Soil samples were collected from each pot for nematode extraction and SCN eggs were counted to determine the final SCN egg density. The population reduction was determined for each crop and nonplanted natural soil (fallow). All of the tested crops and nonplanted natural soil had significantly (P < 0.0001) lower final population densities compared with susceptible soybean (Barnes). Also, a significant difference (P < 0.0001) was observed between the SCN population suppressions caused by cover crops versus the fallow treatment. All cover crops except Austrian winter pea, carinata, faba bean, and foxtail millet had consistently lower SCN egg numbers than in fallow in both years of the experiments. The average population reductions of SCN by the cover crops ranged from 44 to 67% in comparison with the initial population density, while the fallow had natural reductions from 4 to 24%. Annual ryegrass and daikon radish reduced SCN egg numbers to a greater extent than the other cover crops, with an average of 65 and 67% reduction of initial population density, respectively, from 2 years. The results suggested that cover crops reduced the SCN populations in external microplot conditions, and their use has great potential for improving SCN management in infested fields.

On the molecular identity of Paratylenchus nanus (Nematoda: Tylenchida)

In this study, molecular characterization of Paratylenchus nanus collected from the type locality in Four Mile Run, Fall Church, Virginia using COI, D2-D3 of 28 S rRNA and ITS rRNA gene sequences was provided. We molecularly also characterized, Paratylenchus specimens collected from grasses in Devils Lake, Ramsey County, North Dakota indicated as the type locality in the original description of P. nanus by Cobb (1923). These nematodes were identified as representatives of the species P. projectus. Populations of P. nanus belonging to the molecular types A and B, and previously designated by Van den Berg et al. (2014) should be now identified as P. nanus and P. projectus, respectively.

Developing a real-time PCR assay for direct detection and quantification of Pratylenchus scribneri in field soil

The endomigratory root-lesion nematode, Pratylenchus scribneri, is one of the major plant-parasitic nematodes infecting potato. Accurate identification and quantification of this nematode are essential to develop management strategies but microscopic observations are particularly challenging and time consuming. In this study, a SYBR Green I-based real-time quantitative polymerase chain reaction (qPCR) assay was developed to detect and quantify P. scribneri from field soil DNA extracts. A primer set was designed from the internal transcribed spacer (ITS) region of the P. scribneri rDNA gene. Primer specificity to the target nematode was evaluated by both in silico analysis and qPCR and no detection or non-specific amplification was observed for other non-target nematode species/communities tested in this study. Standard curves were generated using DNA extracts from autoclaved soil infested with varying nematode numbers for calibration. The curves were supported by a high correlation between the P. scribneri numbers artificially added to soil or estimated from naturally infested field soils by traditional methods, and the numbers quantified using the qPCR assay. The assay was able to detect 1 out of 128 (0.0078) equivalents of the DNA of a single nematode in 0.5 g of soil. The qPCR assay developed in this study provides a specific and sensitive detection and quantification of P. scribneri from field soils and a rapid alternative to time-consuming traditional nematode identification and enumeration.

[Analysis of drug - resistant gene polymorphisms in Plasmodium falciparum imported from Equatorial Guinea to Shandong Province in 2015 and 2016]

OBJECTIVE

To investigate the drug-resistant gene polymorphisms in Plasmodium falciparum imported from Equatorial Guinea to Shandong Province.

METHODS

From 2015 to 2016, blood samples were collected from imported P. falciparum malaria patients returning from Equatorial Guinea to Shandong Province, and genome DNA of the malaria parasite was extracted. The drug-resistant Pfcrt, Pfmdr1, Pfdhfr, Pfdhps, and K13 genes of P. falciparum were amplified using a PCR assay, followed by DNA sequencing, and the sequences were aligned.

RESULTS

The target fragments of all 5 drug-resistant genes of P. falciparum were successfully amplified and sequenced. There were 72.8%, 18.6%, and 8.6% of P. falciparum parasites carrying the wild-, mutant-, and mixed-type Pfcrt gene, respectively, and all mutant haplotypes were CVIET (the underline indicates the mutation site). There were 20.0%, 61.4% and 18.6% of P. falciparum parasites carrying the wild-, mutant-, and mixed-type Pfmdr1 gene, respectively, and the mutant haplotypes mainly included YF and NF (the underlines indicate the mutation sites). There were 1.4%, 98.6%, and 0 of P. falciparum parasites carrying the wild-, mutant-, and mixed-type Pfdhfr gene, respectively, and AIRNI was the predominant mutant haplotype (the underline indicates the mutation site). There were 1.4%, 94.3%, and 4.3% of P. falciparum parasites carrying the wild-, mutant-, and mixed-type Pfdhps gene, respectively, and SGKAA was the predominant mutant haplotype (the underline indicates the mutation site). The complete drug-resistant IRNGE genotype consisted of 8.6% of the Pfdhfr and Pfdhps genes, and the K13 gene A578S mutation occurred in 1.4% of the parasite samples.

CONCLUSIONS

There are mutations in the Pfcrt, Pfmdr1, Pfdhfr, Pfdhps, and K13 genes of P. falciparum imported from Equatorial Guinea to Shandong Province, with a low frequency in the Pfcrt gene mutation and a high frequency in the Pfmdr1, Pfdhfr, and Pfdhps gene mutations, and the K13 gene A578S mutation is detected in the parasite samples.

Oral delivery of novel human IGF-1 bioencapsulated in lettuce cells promotes musculoskeletal cell proliferation, differentiation and diabetic fracture healing

Human insulin-like growth factor-1 (IGF-1) plays important roles in development and regeneration of skeletal muscles and bones but requires daily injections or surgical implantation. Current clinical IGF-1 lacks e-peptide and is glycosylated, reducing functional efficacy. In this study, codon-optimized Pro-IGF-1 with e-peptide (fused to GM1 receptor binding protein CTB or cell penetrating peptide PTD) was expressed in lettuce chloroplasts to facilitate oral delivery. Pro-IGF-1 was expressed at high levels in the absence of the antibiotic resistance gene in lettuce chloroplasts and was maintained in subsequent generations. In lyophilized plant cells, Pro-IGF-1 maintained folding, assembly, stability and functionality up to 31 months, when stored at ambient temperature. CTB-Pro-IGF-1 stimulated proliferation of human oral keratinocytes, gingiva-derived mesenchymal stromal cells and mouse osteoblasts in a dose-dependent manner and promoted osteoblast differentiation through upregulation of ALP, OSX and RUNX2 genes. Mice orally gavaged with the lyophilized plant cells significantly increased IGF-1 levels in sera, skeletal muscles and was stable for several hours. When bioencapsulated CTB-Pro-IGF-1 was gavaged to femoral fractured diabetic mice, bone regeneration was significantly promoted with increase in bone volume, density and area. This novel delivery system should increase affordability and patient compliance, especially for treatment of musculoskeletal diseases.

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

Factors relating to SYBR Green-based quantitative real-time PCR (qPCR) quantification of stubby root nematode Paratrichodorus allius 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. Soil pre-treatments showed that autoclaved field soil had significantly reduced DNA amount and quality. The air- or oven-dried soil yielded a lower amount of DNA with similar purity, compared with natural field soil. PCR inhibitors were detected in soil DNA substrates targeting pBluescript II SK(+)-plasmid DNA. Al(NH₄)(SO₄)₂ treatment during DNA preparation significantly reduced the inhibitors compared with post-treatment of soil DNA with polyvinylpolypyrrolidone column. The effect of PCR inhibitors on qPCR was suppressed by bovine serum albumin. Quantification results did not significantly change when increasing the number of DNA extractions from three to six per soil sample when soil grinding and grid sampling strategies were used. Two standard curves, generated from serial dilutions of plasmid DNA containing P. allius ITS1 rDNA and soil DNA containing known nematode numbers, produced similar correlations between Cq values and amount of targets. The targets in soil DNA quantified by qPCR using either standard curve correlated well with microscopic observations using both artificially and naturally infested field soils. This is the first study for assessing various factors that may affect qPCR quantification of stubby root nematodes. Results will be useful during the setup or optimization of qPCR-based quantification of plant-parasitic nematodes from soil DNA.

Volatiles from Merino fleece evoke antennal and behavioural responses in the Australian sheep blow fly Lucilia cuprina

To identify flystrike-related volatile compounds in wool from Merino sheep, the attractiveness of wool to Lucilia cuprina Wiedmann (Diptera: Calliphoridae) was examined. First, a selection of wool samples guided by previous knowledge of sheep lines, predicted to be more susceptible or more resistant to flystrike, was tested. The attractiveness of the 10 samples selected was not associated with field susceptibility: two samples from the more resistant line were identified as most attractive and two samples from the more susceptible line were identified as least attractive, based on the behavioural assays with gravid flies. Comparison of the headspace volatiles of these samples, using solid phase microextraction and gas chromatography-mass spectrometry-electroantennographic detection, revealed octanal and nonanal to be present in the attractive wool samples that elicited responses from the fly antenna. Furthermore, the two compounds were not present in wool that was least attractive to L. cuprina. In laboratory bioassays, octanal and nonanal evoked antennal and behavioural responses in gravid L. cuprina, thus confirming their potential role as semiochemicals responsible for attracting L. cuprina to Merino sheep.

P5476Usefulness of haemoglobin level combined with CAMI-STEMI score for predicting MACCE in patients with acute ST-elevation myocardial infarction after PCI

Background

Early risk stratification was strongly recommended to guide therapeutic management and to improve outcome for ST elevation myocardial infarction (STEMI) patients. Anaemia and high haemoglobin levels are common in STEMI patients, but the effect of the haemoglobin level on the prognosis of STEMI patients remains in dispute. The China Acute Myocardial Infarction registry-ST Elevation Myocardial Infarction (CAMI-STEMI) score can predict in-hospital mortality among Chinese STEMI patients, with similar performance to the well-established Thrombolysis in Myocardial Infarction (TIMI) score, while relying solely on simple and practical variables. This study aimed to evaluate the prognostic value of the haemoglobin level combined with the CAMI-STEMI score in STEMI patients after percutaneous coronary intervention (PCI).

Methods

We included 360 STEMI patients who underwent PCI. The patients were divided into 3 groups according to the first haemoglobin value after PCI, group 1 (male: Hb<120 g/L, female: Hb<110 g/L; 42 cases), group 2 (male: 120 g/L ≤ Hb<160 g/L, female: 110 g/L≤Hb<150 g/L; 278 cases), and group 3 (male: Hb ≥160 g/L, female: Hb ≥150 g/L; 40 cases). Clinical characteristics, and the incidence of major adverse cardiovascular and cerebral events (MACCE) during the follow-up period were recorded.

Results

The incidence of MACCE in the 3 groups increased with a decrease in the haemoglobin level. Multivariate regression analysis showed that the CAMI-STEMI score was an independent predictor of MACCE incidence at 30 days after PCI and that anaemia was an independent predictor of MACCE incidence at 6 months and 1 year after PCI. A high haemoglobin level was an independent predictor of MACCE incidence at 1 year after PCI. The area under receiver operating characteristic curves (AUCs) of the haemoglobin level, CAMI-STEMI score and haemoglobin level combined with CAMI-STEMI score predicting the occurrence of MACCE in STEMI patients within 30 days after PCI were 0.604, 0.614, and 0.639, respectively.

Figure 1. MACCE-free survival curve

Conclusion

The CAMI-STEMI score was an independent predictor of MACCE incidence at 30 days after PCI. The haemoglobin level combined with the CAMI-STEMI score improved the predictive value of MACCE in STEMI patients within 30 days after PCI.

Acknowledgement/Funding

This study was supported by grants to Chengchun Tang from the National Natural Science Foundation of China (Research Grant #81670237)

Reproduction Ability and Growth Effect of Pin Nematode, Paratylenchus nanus, With Selected Field Pea Cultivars

Greenhouse experiments were conducted to determine the reproductive ability and effect of the pin nematode Paratylenchus nanus from North Dakota on field pea cultivars. Reproduction of P. nanus was determined on seven field pea cultivars using naturally infested field soils at low (1,500/kg of soil) and high (4,500/kg soil) initial pin nematode densities. Nematode effect on plant growth and seed yield was evaluated at 4,500 P. nanus per 1 kg of soil by artificially inoculating P. nanus on six field pea cultivars. Reproductive factor (RF) of P. nanus was observed to be greater at the low density than the high density of the nematode. At the low population density, RF values ranged from 1.10 to 11.20, whereas at the high density, RF ranged from 1.20 to 2.50. In experiments evaluating P. nanus effects on cultivar growth, the nematode (4,500 P. nanus per 1 kg soil) caused reduction (P < 0.05) of plant height in most cultivars tested, and it also significantly impacted dry shoot weight and dry seed weight in some experiments. Plant height and shoot weight reductions were the highest in the cultivar Arcadia (up to 37 and 53%, respectively), with a dry seed weight reduction up to 32%. This research demonstrated for the first time the negative impact of P. nanus on field peas in controlled greenhouse conditions, which is an important step toward developing effective management strategies to improve the productivity of this leguminous crop.

Susceptibility of Anopheles gambiae complex mosquitoes to microbial larvicides in diverse ecological settings in western Kenya

The microbial larvicides Bacillus thuringiensis var. israelensis (Bti) and Bacillus sphaericus (Bs) (Bacillales: Bacillaceae) are well known for their efficacy and safety in mosquito control. In order to assess their potential value in future mosquito control strategies in western Kenya, the current study tested the susceptibility of five populations of Anopheles gambiae complex mosquitoes (Diptera: Culicidae), collected from five diverse ecological sites in this area, to Bti and Bs under laboratory conditions. In each population, bioassays were conducted with eight concentrations of larvicide (Bti/Bs) in four replicates and were repeated on three separate days. Larval mortality was recorded at 24 h or 48 h after the application of larvicide and subjected to probit analysis. A total of 2400 An. gambiae complex larvae from each population were tested for their susceptibility to Bti and Bs. The mean (± standard error of the mean, SEM) lethal concentration values of Bti required to achieve 50% and 95% larval mortality (LC₅₀ and LC₉₅ ) across the five populations were 0.062  (± 0.005) mg/L and 0.797 (± 0.087) mg/L, respectively. Corresponding mean  (± SEM) values for Bs were 0.058 (± 0.005) mg/L and 0.451 (± 0.053) mg/L, respectively. Statistical analysis indicated that the five populations of An. gambiae complex mosquitoes tested were fully susceptible to Bti and Bs, and there was no significant variation in susceptibility among the tested populations.

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. Traditional diagnosis based on morphology and morphometrics is laborious and requires an experienced taxonomist. Additionally, end-point diagnosis using PCR was only available for P. allius. To increase diagnostic efficiency and reduce costs, a one-step multiplex PCR assay was developed to simultaneously identify these four species using one PCR reaction. Available sequences of 18S ribosomal DNA and internal transcribed spacer 1 (ITS1) region of these species were aligned and five primers were designed. The conserved forward primer located in the 18S region, in combination with the species-specific antisense primer in the ITS1 region, amplified a single distinctive PCR fragment for each species (421/425 bp for P. allius, 190 bp for P. minor, 513 bp for P. porosus, and 353 bp for T. obtusus). In silico analysis with 10 other trichodorid species and experimental analysis using samples with these four species, 20 other plant-parasitic and three non-plant-parasitic nematodes demonstrated high specificity with the primers designed. The multiplex PCR amplified desirable fragments using a set of artificially mixed templates containing one, two, three, or four targeted species. The reliability of multiplex PCR results was demonstrated by using nematode populations isolated from infested fields from diverse geographic regions in eight states. The multiplex PCR-based tool developed in this study for the first time provides a simple, rapid, and cost-friendly assay for accurate diagnosis of the four major trichodorid nematodes in the United States.

Occurrence and distribution of vermiform plant-parasitic nematodes and the relationship with soil factors in field pea (Pisum sativum) in North Dakota, USA

Plant-parasitic nematodes restrict crop growth and cause yield loss in field pea (dry edible pea). A 4-year survey of commercial pea fields was conducted in North Dakota, one of the leading producers of field pea in the USA, to investigate nematode distribution, prevalence, abundance and association with soil properties. Beginning in 2014, a total of 243 soil samples were collected from 16 counties, and soil properties of 115 samples were analysed to determine the association of nematodes with soil factors (texture, organic matter, nutrients). The plant-parasitic nematode genera, Paratylenchus (absolute frequency = 58-100%; mean density = 470-1550 (200 g soil)−1; greatest density = 7114 (200 g soil)−1) and Tylenchorhynchus (30-80%; 61-261; 1980, respectively), were the most frequent and widely distributed. Pratylenchus and Helicotylenchus were identified in one-third of the counties surveyed with mean densities ranging from 43 to 224 and 36 to 206 (200 g soil)−1, respectively. Xiphinema was found relatively frequently but at low densities. Hoplolaimus and Paratrichodorus were rarely detected at lower densities. Canonical correspondence analysis revealed that soil factors explained 19% of the total variance of nematode genera abundance. The relationship between nematode abundance and soil sand content and pH was significant, while clay, silt, organic matter and nutrients were not significantly related to nematode abundance. This is the first multi-year study investigating nematodes associated with field peas and their relationship with soil factors in a major field pea production region of the USA.

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. SRN were found in 106 soil samples with population densities of 10 to 320 SRN per 200 g of soil and in eight of the nematode suspensions. Sequencing of ribosomal DNA (rDNA) or species-specific polymerase chain reaction assays revealed the presence of four SRN species, including Paratrichodorus allius, P. minor, P. porosus, and Trichodorus obtusus. Accordingly, their rDNA sequences were characterized by analyzing D2-D3 of 28S rDNA, 18S rDNA, and internal transcribed spacer (ITS) rDNA obtained in this study and retrieved from GenBank. Both intra- and interspecies variations were higher in ITS rDNA than 18S rDNA and D2-D3 of 28S rDNA. Based on phylogenetic analysis, the four SRN species formed a monophyletic group, with P. allius more closely related to P. porosus than P. minor and T. obtusus. Indel variation of ITS2 rDNA was present in P. allius populations from the same geographic regions. This study documented the occurrence of SRN species across multiple states. The intra- and interspecies genetic diversity of rDNA in this study will provide more information for understanding the evolutionary relationships of SRN and will be valuable for future studies of SRN species identification and management.

An Algal Diet Accelerates Larval Growth of Anopheles gambiae (Diptera: Culicidae) and Anopheles arabiensis (Diptera: Culicidae)

The population sizes of Anopheles gambiae Giles (Diptera: Culicidae) and Anopheles arabiensis Patton (Diptera: Culicidae) increase dramatically with the onset of the rainy season in sub-Saharan Africa, but the ecological mechanisms underlying the increases are not well understood. As a first step toward to understand, we investigated the proliferation of algae, the major food of mosquito larvae, in artificial fresh water bodies exposed to sunlight for a short period, and old water bodies exposed to sunlight for a long period, and the effects thereof on the development of these anopheline larvae. We found that an epizoic green algal species of the genus Rhopalosolen (Chlorophyta: Chlorophyceae) proliferated immediately after water freshly taken from a spring was placed in sunlight. This alga proliferated only briefly (for ~10 d) even if the water was repeatedly exposed to sunlight. However, various algal species were observed in water that remained under sunlight for 40 d or longer (i.e., in old water bodies). The growth performance of larvae was higher in sunlight-exposed (alga-rich) water than in shade-stored (alga-poor) water. Stable isotope analysis suggested that these two anopheline species fed on Rhopalosolen algae in fresh water bodies but hardly at all on other algae occurring in the old water bodies. We concluded that freshly formed ground water pools facilitate high production of anopheline species because of the proliferation of Rhopalosolen algae therein, and the increase in the number of such pools in the rainy season, followed by rapid increases in A. gambiae and A. arabiensis numbers.