Acoustic difference in advertisement calls among two sympatric Boulenophrys species: A confirmatory case to acoustic niche hypothesis and morphological constraint hypothesis.

In anurans, acoustic communication is the most important form of communication at the interspecific and intraspecific levels. Acoustic diagnostic features may be a potential alternative to morphometric and molecular diagnostics. Here, we assessed the variations in advertisement calls between two sympatric species, Boulenophrys leishanensis and Boulenophrys spinata, that share their breeding season and breeding sites. In addition, we investigated any potential relationships between call parameters and body size. We found that the advertisement calls of both species are simple calls. The two species exhibited significant differences in all call parameters. Both B. leishanensis and B. spinata showed a significant negative correlation with their body size on dominant frequency. These differences in call parameters may play an important role in interspecific recognition. Additionally, because intraspecific acoustic variation reflects body size, calls may be relevant for sexual selection. Our study supports the acoustic niche hypothesis and the morphological constraint hypothesis and calls are a valid tool for distinguishing between the two species of Boulenophrys in the field.

A broad host phage, CP6, for combating multidrug-resistant Campylobacter prevalent in poultry meat.

Campylobacter is a major cause of bacterial foodborne diarrhea worldwide. Consumption of raw or undercooked chicken meat contaminated with Campylobacter is the most common causative agent of human infections. Given the high prevalence of contamination in poultry meat and the recent rise of multi-drug-resistant (MDR) Campylobacter strains, an effective intervention method of reducing bird colonization is needed. In this study, the Campylobacter-specific lytic phage CP6 was isolated from chicken feces. Phage CP6 exhibited a broad host range against different MDR Campylobacter isolates (97.4% of strains were infected). Some biological characteristics were observed, such as a good pH (3-9) stability and moderate temperature tolerance (<50 ℃). The complete genome sequence revealed a linear double-stranded DNA (178,350 bp, group II Campylobacter phage) with 27.51% GC content, including 209 predicted open reading frames, among which only 54 were annotated with known functions. Phylogenetic analysis of the phage major capsid protein demonstrated that phage CP6 was closely related to Campylobacter phage CPt10, CP21, CP20, IBB35, and CP220. CP6 phage exerted good antimicrobial effects on MDR Campylobacter in vitro culture and reduced CFUs of the host cells by up to 1-log compared with the control in artificially contaminated chicken breast meat. Our findings suggested the potential of CP6 phage as a promising antimicrobial agent for combating MDR Campylobacter in food processing.

A new odorous frog species of Odorrana (Amphibia, Anura, Ranidae) from Guizhou Province, China.

The frog genus Odorrana is distributed across east and southeastern Asia. Based on morphological differences and molecular phylogenetics, a new species of the genus occurring from Leigong Mountain in Guizhou Province, China is described. Phylogenetic analyses based on DNA sequences of the mitochondrial 12S rRNA, 16S rRNA, and ND2 genes supported the new species as an independent lineage. The uncorrected genetic distances between the 12S rRNA, 16S rRNA, and ND2 genes between the new species and its closest congener were 5.0%, 4.9%, and 16.3%, respectively. The new species is distinguished from its congeners by a combination of the following characters: body size moderate (SVL 39.1-49.4 mm in males, 49.7 mm in female); head width larger than head length; tympanum distinctly visible; small rounded granules scattered all over dorsal body and limbs; dorsolateral folds absent; heels overlapping when thighs are positioned at right angles to the body; tibiotarsal articulation reaching the level between eye to nostril when leg stretched forward; vocal sacs absent in male and nuptial pads present on the base of finger I.

Effectiveness of Problem-Based Learning on Development of Nursing Students' Critical Thinking Skills: A Systematic Review and Meta-analysis.

BACKGROUND: Problem-based learning (PBL) is a student-centered approach to teaching that has been applied in medical and nursing education. The effectiveness of PBL in promoting critical thinking in nursing students has been studied extensively with mixed results. PURPOSE: The meta-analysis aimed to investigate the impact of PBL interventions on critical thinking skills of nursing students. METHODS: PubMed, Embase, Cochrane, and CINAHL databases were electronically searched. Methodological quality was examined using the Newcastle-Ottawa Scale and version 2 of the Cochrane risk-of-bias tool. Data were analyzed with 95% confidence intervals based on random-effect models. RESULTS: Nineteen studies involving 1996 nursing students were included in the analysis. The results of the analysis demonstrated greater improvement in critical thinking skills compared with the control group (overall critical thinking scores: standardized mean difference [SMD] = 0.47, 95% CI = 0.33-0.61, P < .01). CONCLUSIONS: The meta-analysis indicates that PBL can help nursing students to improve their critical thinking.

Effects of soil factors on dimethyl disulfide desorption and the risk of phytotoxicity to newly-planted seedlings.

Dimethyl disulfide (DMDS) is a relatively new soil fumigant used in agro-industrial crop production to control soil-borne pests that damage crops and reduce yield. The emissions of DMDS after fumigation reduce soil concentrations thus reducing the risk of phytotoxicity to newly planted crops. However, the factors affecting the desorption of DMDS from soil are unclear. In our study, the desorption characteristics of DMDS from soil were measured in response to continuous ventilation. The degradation of DMDS in soil was examined by thermal incubation. The phytotoxic response of newly-planted cucumber (Cucumis sativus) seedlings to DMDS residues was measured by a sand culture experiment. The results showed DMDS desorption and degradation rates fit a first-order model; that 92% of the DMDS desorption occurred in the first hour after fumigant application; and that residue concentrations in the soil at the end of the ventilation period were unlikely to be phytotoxic to newly-planted cucumber seedlings. By the third day of ventilation, the average desorption rate (ADR) of DMDS in Wenshan soil was 4.0 and 3.6 times, respectively, faster than that in Shunyi and Suihua soils and the ADR of DMDS in soil decreased by 40.0% when the soil moisture content increased from 3% to 12% (wt/wt). Moreover, within one hour of ventilation, the ADR of DMDS in soil decreased by 20.1% when the soil bulk density increased from 1.1 to 1.3 g cm-3. The degradation of DMDS in soil, however, was mostly influenced by soil type and moisture content. A slow degradation rate resulted in a high initial desorption concentration of DMDS in soil. Our results indicated that DMDS desorption from soil in response to continuous ventilation was affected by the soil type, moisture content and bulk density. Rapid degradation of DMDS in soil will lower the risk of phytotoxic residues remaining in the soil and reduce emissions during the waiting period. Acceleration of emissions early in the waiting period by managing soil moisture content or increasing soil porosity may shorten the duration of emissions. Alternatively, soil extraction technology could be developed to recover and reduce fumigant emissions.

[Effectiveness of temporal island flap pedicled with perforating branch of zygomatic orbital artery to repair the defects after periocular malignant tumor resection].

Objective: To summarize the effectiveness of the temporal island flap pedicled with the perforating branch of zygomatic orbital artery for repairing defects after periocular malignant tumor resection. Methods: Between January 2015 and December 2020, 15 patients with periocular malignant tumors were treated. There were 5 males and 10 females with an average age of 62 years (range, 40-75 years). There were 12 cases of basal cell carcinoma and 3 cases of squamous carcinoma. The disease duration ranged from 5 months to 10 years (median, 2 years). The size of tumors ranged from 1.0 cm×0.8 cm to 2.5 cm×1.5 cm, without tarsal plate invasion. After extensive resection of the tumors, the left defects in size of 2.0 cm×1.5 cm to 3.5 cm×2.0 cm were repaired with the temporal island flap pedicled with the perforating branch of zygomatic orbital artery via subcutaneous tunnel. The size of the flaps ranged from 3.0 cm×1.5 cm to 5.0 cm×2.0 cm. The donor sites were separated subcutaneously and sutured directly. Results: All flaps survived after operation and the wounds healed by first intention. The incisions at donor sites healed by first intention. All patients were followed up 6-24 months (median, 11 months). The flaps were not obviously bloated, the texture and color were basically the same as the surrounding normal skin, and the scars at recipient sites were not obviously. There was no complication such as ptosis, ectropion, or incomplete closure of the eyelids and recurrence of tumor during follow-up. Conclusion: The temporal island flap pedicled with the perforating branch of zygomatic orbital artery can repair the defects after periorbital malignant tumors resection and has the advantages of reliable blood supply, flexible design, and good morphology and function.

Detection of AmpC ß-lactamases in gram-negative bacteria.

AmpC ß-lactamase genes are clinically important because they often confer resistance to most ß-lactams other than 4th-generation cephalosporins and carbapenems. However, traditional and existing detection methods are expensive, labor-intensive and range-limited. We established an efficient multiplex PCR method to simultaneously identify six families of ampC ß-lactamase genes, ACC, EBC, CIT, DHA, MOX and FOX, and evaluated the sensitivity and specificity of this assay. The multiplex method could accurately identify ACC, EBC, CIT, DHA, MOX and FOX variants among a total of 175 ampC ß-lactamase genes. The minimum concentration of genomic DNA that could be detected was 1.0×103 copies/µL. We subsequently used this method to analyze 2 Salmonella spp. with carrying CMY-2 and DHA-1, and 167 Enterobacteriaceae isolates in blinded PCR testing. Positive isolates produced bright bands that corresponded with their genotype. Results were in concordance with those of the traditional method but showed increased sensitivity and accuracy. This indicates that the newly developed multiplex PCR system could be used as a diagnostic tool to accurately distinguish the six families of ampC ß-lactamase genes with high efficiency, wide range, easy operation and good discrimination.

Effects of fertilizers and soil amendments on the degradation rate of allyl isothiocyanate in two typical soils of China.

BACKGROUND: Allyl isothiocyanate (AITC) is a soil fumigant that protects plants against soil-borne pathogens, weeds and insects when present in the root-zone. However, the degradation of AITC under different fertilizers and soil amendments affects its emission and pest control efficacy. Degradation rates of AITC in soil amended with organic and inorganic fertilizers, zeolite and biochar were determined in the laboratory to improve its field applications. RESULTS: The degradation half-lives of AITC were 24.4 and 35.4 h in Fangshan and Yongzhou soils, respectively, without any added fertilizer or soil amendment. Nitrogen fertilizer and organic fertilizer accelerated the degradation rate of AITC, while phosphorus fertilizer had the opposite effect. The degradation rate of AITC on adding unsterilized chicken manure was over 3.5 and 1.1 times higher than that of sterilization in Fangshan and Yongzhou soil. Inorganic and organic fertilizers affected the degradation of AITC by affecting soil microbial activity on the basis of CO2 cumulative release. The degradation rate of AITC increased more than 0.4 times in response to zeolite, but this was independent of particle size. The AITC degradation rate increased 1.0-2.6 and 0.3-9.7 times in response to biochar made from corn stalk and pine wood, respectively. Cow manure biochar manufactured at different pyrolyzation temperatures had different effects on the degradation rate of AITC. CONCLUSION: Soil type, fertilizers and soil amendments differentially affect the degradation rate of AITC by changing soil physicochemical characteristics, microorganisms, etc., which shows great potential in reducing AITC emissions and increasing pest control efficacy when AITC is applied commercially. © 2022 Society of Chemical Industry.

Protective effects of fowl-origin cadmium-tolerant lactobacillus against sub-chronic cadmium-induced toxicity in chickens.

Cadmium (Cd) directly endangers poultry health and indirectly causes harm to human health by food chain. Numerous studies have focused on removing Cd using lactic acid bacteria (LAB). However, there is still a lack of in vivo studies to validate whether Cd can be absorbed successfully by LAB to alleviate Cd toxicity. Here, we aimed to isolated and screened poultry-derived Cd-tolerant LAB with the strongest adsorption capacity in vitro and investigate the protective effect of which on sub-chronic Cd toxicity in chickens. First, nine Cd-tolerant LAB strains were selected preliminarily by isolating, screening, and identifying from poultry farms. Next, four strains with the strongest adsorption capacity were used to explore the influence of different physical and chemical factors on the ability of LAB to adsorb Cd as well as its probiotic properties in terms of acid tolerance, bile salt tolerance, drug resistance, and antibacterial effects. Resultantly, the CLF9-1 strain with the best comprehensive ability was selected for further animal protection test. The Cd-tolerant LAB treatment promoted the growth performance of chickens and reduced the Cd-elevated liver and kidney coefficients. Moreover, Cd-induced liver, kidney, and duodenum injuries were alleviated significantly by high-dose LAB treatment. Furthermore, LAB treatment also increased the elimination of Cd in feces and markedly reduced the Cd buildup in the liver and kidney. In summary, these findings determine that screened Cd-tolerant LAB strain exerts a protective effect on chickens against sub-chronic cadmium poisoning, thus providing an essential guideline for the public health and safety of livestock and poultry.

Refractory thrombocytopenia could be a rare initial presentation of Noonan syndrome in newborn infants: a case report and literature review.

BACKGROUND: Noonan syndrome (NS) is a relatively rare inherited disease. Typical clinical presentation is important for the diagnosis of NS. But the initial presentation of NS could be significant variant individually which results in the difficult of working diagnosis. Here we report a rare neonatal case of NS who presented with refractory thrombocytopenia as the initial manifestation. CASE PRESENTATION: This was a preterm infant with refractory thrombocytopenia of unknown origin transferred from obstetric hospital at 6 weeks of age. During hospitalization, typical phenotypes of NS in addition to thrombocytopenia were observed, such as typical facial characteristics, short stature, atrial septal defect, cryptochidism, coagulation defect and chylothorax. Genetic testing showed a pathogenic variant at exon 2 of the PTPN11 gene with c.124A > G (p.T42A). Respiratory distress was deteriorated with progressive chylothorax. Chest tube was inserted for continuous draining. Chemical pleurodesis with erythromycin was tried twice, but barely effective. Finally, parents decided to withdraw medical care and the patient died. CONCLUSIONS: Thrombocytopenia could be the first symptom of Noonan syndrome. After ruling out other common causes of thrombocytopenia, NS should be considered as the working diagnosis.

Soil properties affect vapor-phase adsorption to regulate dimethyl disulfide diffusion in soil.

Dimethyl disulfide (DMDS) is efficacious against nematodes and other soil-borne pathogens known to reduce crop quality and yield. Previous studies reported inconsistent efficacy and suggested that the diffusion of DMDS varied with different soil types. The effect of soil adsorption on gaseous DMDS diffusion through different soil types is poorly understood. To clarify the role and mechanism of soil adsorption in the diffusion of gaseous DMDS in soil, we have studied the diffusion rate constant (Rt) of gaseous DMDS in soils using a soil column experiment. The adsorption of DMDS at each gas-soil, soil-water and gas-water partition was measured by a batch-equilibrium headspace method. The results showed the DMDS adsorption equilibrium was well-described by the nonlinear Freundlich isotherm and the linear Henry isotherm. Rt values were strongly negatively correlated with the Henry coefficient (Kd) values. The Kd values of dry soil were several orders of magnitude higher than those observed in moist soil within each moisture content range. The Kd values in dry soil were strongly positively correlated with soil pore size (<2 nm). However, when the soil moisture content ranged from 3 to 12% (w/w), the Kd values were strongly correlated with specific surface area (SSA). Elevated temperatures promoted the gaseous phase of DMDS (consistent with Henry's Law) and its diffusion through soil. The soil-water partition coefficient (K'f) ranged from 1.83 to 2.20 µg11/n mL1/n g-1 in tested soils. Our results suggest that the DMDS vapor-phase diffusion in soil was significantly affected by soil adsorption, which in turn depended on the soil's properties especially the SSA and soil moisture content. These findings suggest applicators can reduce the risk of unsatisfactory and inconsistent efficacy results against soil-borne pests by adjusting the DMDS dose and fumigation period according to soil type, moisture conditions, and other environmental factors.

Characterization and phylogenetic evolution of mitochondrial genome in Tibetan chicken.

The objective of this study was to characterize mitochondrial genome and investigate phylogenetic evolution in Tibetan chicken. In this study, four haplotypes were identified based on D-loop sequencing in Tibetan chicken (n = 40), and each representative of four haplotypes was selected for total mitochondrial genome sequencing and analyzed together with published mitochondrial genome data of red jungle fowl. Four haplotypes belonged to three previously published clades, i.e., Clade A, clade B and clade E. Based on D-loop sequencing data, the average haplotype diversity and nucleotide diversity were 0.658 ± 0.065 and 0.00442 ± 0.00094, respectively. The mitochondrial genome of Tibetan chicken is 16,785 bp in size, consisting of 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, 13 protein-coding genes and one non-coding control region (CR). Compared with the mitochondrial genome, a phylogenetic tree based on the D-loop sequence had a messy distribution, and no breed cluster pattern was observed in Tibetan chicken. The results indicate that Tibetan chicken populations in our study have relatively low nucleotide and haplotype diversity and likely share multiple maternal lineages. The D-loop sequence has limited power for the resolution of phylogenetic relationships in comparison with the complete mitochondrial genome.

Factors Underlying the Prevalence of Pythium Infection of Corn Seeds Following Seed Treatment Application of Tebuconazole.

Microbial communities are essential for soil health, but fungicide application may have significant effects on their structure. It is difficult to predict whether nontarget pathogens of applied fungicides in the soil will cause crop damage. Tebuconazole is a triazole fungicide that can be used as a seed treatment and, thereby, introduced to the soil. However, seed-applied tebuconazole has a potential risk of causing poor emergence of corn (Zea mays) seedlings. Using soil with a history of poor corn seedling emergence, we demonstrate through TA cloning and isolation that the poor emergence of corn seedlings from tebuconazole-coated corn seeds was primarily because of infection by surviving soil pathogens, specifically Pythium species that are not targeted by tebuconazole, rather than the phytotoxic effects of tebuconazole. Bioassay tests on tebuconazole-amended media showed that tebuconazole can suppress soil fungi while allowing Pythium to grow. Pythium species primarily contributing to the corn seed rot were more pathogenic at cooler temperatures. Furthermore, the nontarget biocontrol agent of Trichoderma spp. was strongly inhibited by tebuconazole. Taken together, the nontarget effects of tebuconazole are likely not significant under favorable plant growing conditions but are considerable because of low-temperature stress.

2-Hydroxypropyl-ß-cyclodextrin encapsulates dimethyl disulfide producing a controlled release formulation.

Dimethyl disulfide (DMDS), a soil fumigant, is an effective, broad-spectrum compound that often replaces bromomethane (MB) in the prevention and treatment of soil-borne diseases. However, the disadvantages of DMDS include toxicity, volatility, pungent odor, risk of human exposure, and environmental pollution. Cyclodextrin (CD) has been widely used as a carrier of chemicals in many industries due to its functional advantages and safety. In this study, a DMDS-controlled release formulation was developed by encapsulating DMDS in the cavity of 2-hydroxypropyl-ß-cyclodextrin (HP-ß-CD). This formulation reduced DMDS usage and production costs. Orthogonal experimental design, Fourier transform infrared (FT-IR), Scanning electron microscopy (SEM), Thermal gravity analysis (TGA) characterization, efficacy comparison, safety, and other aspects of the evaluation showed that under the best preparation conditions, the encapsulation rate was 81.49%. The efficacy of DMDS@HP-ß-CD was similar to unformulated DMDS. The efficacy duration of the formulation was about two times longer than DMDS, and it was safer to use. This study reveals a cyclodextrin-DMDS formulation with reduced toxicity, longer duration, environmental safety and sustainability.

Antibiotic Resistance Profiles and Molecular Mechanisms of Campylobacter From Chicken and Pig in China.

The purpose of this research was to characterize the antibiotic resistance profiles of Campylobacter spp. derived from chicken and pig feces collected from farms in Jiangsu Province, China, and to analyze the relevant resistance mechanisms among antimicrobial-resistant Campylobacter spp. isolates. Antibiotic susceptibility to nine antibiotic agents was tested with the microdilution method in 93 Campylobacter spp. (45 C. jejuni and 25 C. coli from chickens; 23 C. coli from pigs). High rates of resistance were observed to nalidixic acid (79.6%), erythromycin (75.3%), tetracycline (68.8%), azithromycin (66.7%), ciprofloxacin (64.5%), and gentamicin (35.5%), with a lower resistance rate to florfenicol (8.6%). The prevalence of the tested antibiotic resistance in C. coli was higher than in C. jejuni from chickens. The rate of antimicrobial resistance to ciprofloxacin in C. coli isolates from chickens was 100.0%, and the C. coli isolates from pigs were all resistant to erythromycin (100%). Most of C. jejuni (64.4%) and C. coli (64.5%) isolates displayed multi-drug resistance. All the Campylobacter spp. isolates resistant to fluoroquinolones had the C257T mutation in the gyrA gene. All 64 tetracycline-resistant Campylobacter spp. isolates were positive for the tetO gene. The tetA gene was also amplified in 6.5% of Campylobacter spp. isolates, whereas tetB was not detected among the isolates. The A2075G point mutation in the 23S rRNA gene occurred in 86.1% (62/72) of the macrolides-resistant Campylobacter spp. isolates, and the ermB gene was identified in 49 Campylobacter spp. isolates (30 C. jejuni and 19 C. coli). Amino acid insertions or mutations in the L4 and L22 ribosomal proteins were not linked to macrolide resistance. These results highlight the high prevalence of resistance to multiple antibiotics, particular macrolides, among Campylobacter spp. from chickens and pigs in Jiangsu Province, China, which is probably attributable to the overuse of antimicrobials in chicken and pig production. These findings recommend the more cautious use of critical antimicrobial agents in swine and poultry production. Stringent and continuous surveillance is required to reduce the drug-resistant campylobacteriosis in food animals and humans.

First Report of Pythium torulosum Causing Corn Root Rot in Northeastern China.

In October 2017, we collected five soil samples from each of several fields with a history of severe corn (Zea mays) seedling disease in Heilongjiang province of China. Affected seedlings were wilted with severe root rot, and a high incidence of seedling death was observed in the fields. Corn seeds were seeded in the collected soil samples and grown in a growth chamber for 21 days set at the following incubation temperatures: 21℃/7℃ for 6 days, 10℃/3℃ for 4 days, 16℃/7℃ for 5 days, 20℃/20℃ for 6 days (16 h/8 h, light/dark) (Tang et al. 2019). The corn seedlings in the growth chamber showed the same symptoms observed in the field as mentioned above. Corn root rot samples were collected from several symptomatic plants in the growth chamber to isolate the possible pathogen. Symptomatic roots were washed in 0.5% NaOCl for 2 min, rinsed in sterile water and cut into 1-2 mm segments and then plated on corn meal agar amended with pimaricin (5 µg/ml), ampicillin (250 µg/ml), rifampicin (10 µg/ml), pentachloronitrobenzene (50 µg/ml), and benomyl (10 µg/ml) (PARP+B), which is selective for oomycetes (Jeffers and Martin 1986). After 3 days of incubation in the dark at 25℃, colonies were transferred to 10% V8 juice agar and incubated at 25℃ for 2 weeks. Six isolates were identified as Pythium torulosum based on the morphology of sexual and asexual structures following van der Plaats-Niterink's key (van der Plaats-Niterink 1981). On 10% V8 juice agar, the hypha were aseptate and colonies had filamentous sporangia with a dendroid or globose structure. The oogonia were globose or subglobose, laevis, terminal, rarely intercalary, ranging from 12-19 (average 16) µm. Antheridia were mostly sessile or brachypodous, and each oogonium was supplied by 1-2 antheridia cells. Oospores were globose, plerotic, ranging from 9-16 (average 13) µm. For the molecular identification, two molecular targets, the internal transcribed spacer (ITS) region of ribosomal DNA and cytochrome c oxidase subunit II (CoII), were amplified and sequenced using universal primer sets DC6/ITS4 (Cooke et al. 2000) and FM58/FM66 (Villa et al. 2006), respectively for one isolate, "copt". BLAST analyses of a 971 bp ITS segment amplified from copt (GenBank Accession No. MT830918) showed 99.79% identity with a P. torulosum isolate (GenBank Accession No. AY598624.2). For the COⅡ gene of copt, BLAST analyses of a 553 bp segment (GenBank Accession MT843570) showed 98.37% identity with P. torulosum isolate (GenBank Accession No. AB095065.1). Thus, the isolate, copt, was identified as P. torulosum based on morphological characteristics and molecular analysis. To confirm pathogenicity and Koch's postulates, a pathogenicity test was conducted as described by Zhang et al. (2000). Briefly, a 5 mm culture plug from the P. torulosum isolate, copt, was transferred to a 9-cm petri dish containing 20mL 10% V8 juice agar and incubated in the dark at 25℃ for 7 days. The culture was cut into small pieces and mixed with a sterilized soil mix (40% organic peat substrate, 40% perlite, and 20% soil) at a ratio of one petri dish per 100 g soil mix. Ten corn seeds were planted at a depth of 2 cm in a 500-mL pot containing the inoculated soil mix. The control pots were mock inoculated with plain 10% V8 juice agar. Pots were incubated in a greenhouse at temperatures ranging from 21 to 23℃. There were four replications. After 14 days, corn roots brown and rotted were observed, which was similar to those observed in the field and growth chamber. Control plants remained symptomless and healthy. P. torulosum copt was consistently re-isolated from the symptomatic roots. To our knowledge, this is the first report of P. torulosum causing root rot of corn in Northeastern China. Corn is an important crop in Heilongjiang and the occurrence of root rot caused by this pathogen may be a new threat to corn plants. There is a need to develop management measures to control the disease.

First Report of Pythium sylvaticum Causing Corn Root Rot in Northeastern China.

As one of the most planted crops worldwide, corn has continuously increased in importance in China over the last decade. But in recent years, poor stands of corn seedlings have occurred frequently in northeastern China, causing significant economic loss. Mature plants were stunted, the roots were necrotic, and some plants collapsed. We collected soil samples from 5 fields with a history of poor stands of corn seedlings in the Heilongjiang province of China in October 2017. After being planted in the collected soil for 12 days, corn seedlings were uprooted. The pathogen was then isolated as described by Tang et al. (2019). Briefly, the rotted roots were washed in 0.5% NaOCl for 2 min, rinsed in sterile water, and then cut into 1-2 mm segments and placed on cornmeal agar amended with pimaricin (5 µg/ml), ampicillin (250 µg/ml), rifampicin (10 µg/ml), pentachloronitrobenzene (50 µg/ml), and benomyl (10 µg/ml) (PARP+B), which is selective for oomycetes (Jeffers and Martin 1986). After 3 days of incubation in the dark at 25℃, colonies were transferred to 10% V8 juice agar or potato dextrose agar (PDA) and grown for 7 days at 25℃. Based on morphological characteristics, one putative isolate (COPS) was identified as P. sylvaticum (Campbell and Hendrix 1967). On PDA, the culture (COPS) produced creamy white and floccus mycelium. P. sylvaticum (COPS) produced hyphal swellings, but no oogonia or zoospore. Hyphal swellings were globose, terminal, or intercalary, ranging from 12.22-18.55 µm diam. Sequence analysis was performed with the cytochrome c oxidase subunit Ⅱ (COⅡ) gene amplified with primers FM35/FM52 (Martin 2000) and the rDNA ITS amplified with primers DC6/ITS4 (Cooke et al. 2000). For COⅡ gene, BLAST analyses of the 773 bp segments showed 97.93% identity with P. sylvaticum isolate (GenBank Accession No. GU222164.1). For the ITS, BLAST analyses of the 880 bp segments showed 99.89% identity with P. sylvaticum isolate (GenBank Accession No. KY084736.1). Both sequences were submitted to GenBank with accession numbers MK648400 and MK606071 for COⅡ and ITS, respectively. For pathogenicity tests, similar to that described by Ling et al. (2018), four 9-cm petri plates containing 20 mL of 10% V8 juice agar were inoculated with an agar plug (5 mm diam) obtained from a 7-day-old P. sylvaticum culture (COPS) grown on 10% V8 juice agar and then incubated at 25℃ in the dark for 7 days. Nine corn seeds were placed on each plate, after which the plates were filled with 50 g sterilized organic peat substrate. For the controls, seeds were placed on non-inoculated plates of 10% V8 juice agar and filled with 50 g sterilized organic peat substrate. Four replications were inoculated. Plates were maintained in a greenhouse at 23℃. After 14 days, similar symptoms as to those observed in the field were present in the greenhouse, whereas control plants remained symptomless. P. sylvaticum (COPS) was re-isolated from diseased roots as described above, thus confirming Koch's postulates. To our knowledge, this is the first report of P. sylvaticum on corn in China. This pathogen may pose a risk to corn production. The identification of the pathogen will help to develop effective strategies to control the disease.

Uptake and translocation of imidacloprid via seed pathway and root pathway during early seedling growth of corn.

BACKGROUND: A systemic seed treatment can be taken up into shoot tissues during early corn seedling growth. However, the pathway that a systemic compound is taken up, either from seed or root uptake to shoot tissues is not fully understood. To study the single contributions of seed pathway and root pathway for the uptake and translocation of imidacloprid seed treatment, two methods were developed: A seed treatment method and a growing media/hydroponic solution delivery method. The seed treatment method employed a live and dead seed separated with plastic wrap to provide a barrier. The growing media/hydroponic solution delivery method quantified the capacity for uptake by seeds and roots. RESULTS: The seed pathway transported 1.9-2.5 times more imidacloprid into shoot tissues when compared to the root pathway at the same dosage rate. The higher amount of imidacloprid taken up and translocated by the seed pathway was attributed to the fact that the corn seeds were in direct contact with high provided concentrations of imidacloprid. However, the root pathway showed 7.9-9.5 times higher capacity for transporting imidacloprid into shoot tissues when compared with the seed pathway. Whenever imidacloprid was taken up by seed or root, amounts of imidacloprid were measured in both tissues of seed and root. CONCLUSION: The seed pathway transported more imidacloprid than the root pathway during early seedling growth since corn seeds were contacted by higher concentrations of imidacloprid. Both seed pathway and root pathway were occurring concurrently during early seedling growth of corn. © 2020 Society of Chemical Industry.