An interpretation for the components of 2p3/2core level x-ray photoelectron spectra of the cations in some inverse spinel oxides.

In an effort to reconcile the various interpretations for the cation components of the 2p3/2observed in x-ray photoelectron spectroscopy (XPS) of several spinel oxide materials, the XPS spectra of both spinel alloy nanoparticles and crystalline thin films are compared. We observed that different components of the 2p3/2core level XPS spectra, of these inverse spinel thin films, are distinctly surface and bulk weighted, indicating surface-to-bulk core level shifts in the binding energies. Surface-to-bulk core level shifts in binding energies of Ni and Fe 2p3/2core levels of NiFe2O4thin film are observed in angle-resolved XPS. The ratio between surface-weighted components and bulk-weighted components of the Ni and Fe core levels shows appreciable dependency on photoemission angle, with respect to surface normal. XPS showed that the ferrite nanoparticles NixCo1-xFe2O4(x= 0.2, 0.5, 0.8, 1) resemble the surface of the NiFe2O4thin film. Surface-to-bulk core level shifts are also observed in CoFe2O4and NiCo2O4thin films but not as significantly as in NiFe2O4thin film. Estimates of surface stoichiometry of some spinel oxide nanoparticles and thin films suggested that the apportionment between cationic species present could be farther from expectations for thin films as compared to what is seen with nanoparticles.

A panel of qPCR assays to detect and quantify soybean soil-borne pathogens.

Fusarium oxysporum,F. graminearum,F. acuminatum,F. equiseti,F. proliferatum,F. solani, and Rhizoctonia solani are soil-borne fungal pathogens that cause substantial yield loss in a widespread list of crops worldwide. The objective of this study was to develop a panel of TaqMan assays for the detection and quantification of these six widespread soil-borne fungal species using real-time polymerase chain reaction (qPCR). The primers and probes were designed based on the intergenic spacer ribosomal RNA and translation elongation factor 1-alpha gene (tef1). These assays, although not multiplexed, can be performed simultaneously as they have similar reaction conditions, allowing more efficiency when targeting multiple pathogens in a sample. The assays presented high efficiency (94.3%-108.9%) and sensitivity, with a limit of detection of 0.05 picograms (50 femtograms) of target DNA. Results from an assay targeting 19 non-target and closely related species confirmed the specificity of the developed assays. The assays were also evaluated to detect the target species in different matrices, such as soil and plant material. This panel of qPCR assays is an additional tool that can be used by plant pathologists, microbiologists, plant breeders, diagnostic clinics, and other researchers interested in these fungal species.

Fluopyram activates systemic resistance in soybean.

The soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is a significant yield-limiting factor in soybean production in the Midwestern US. Several management practices are implemented to mitigate yield losses caused by SCN, including using SDHI (succinate dehydrogenase inhibitors) fungicides delivered as seed treatments. A set of studies was conducted to evaluate the effect of two seed-applied succinate dehydrogenase inhibitors (SDHI) compounds, fluopyram and pydiflumetofen, on SCN population densities, plant injury, and plant growth. Cyst counts in untreated control and pydiflumetofen treated plants were 3.44 and 3.59 times higher than fluopyram, respectively, while egg counts were 8.25 and 7.06 times higher in control and pydiflumetofen. Next-generation sequencing was later employed to identify transcriptomic shifts in gene expression profiles in fluopyram and pydiflumetofen -treated seedlings. RNA expression patterns of seed treatments clustered by sampling time (5 DAP vs. 10 DAP); therefore, downstream analysis was conducted by timepoint. At 5 DAP, 10,870 and 325 differentially expressed genes (DEG) were identified in fluopyram and pydiflumetofen, respectively. These same treatments generated 219 and 2 DEGs at 10 DAP. Multiple DEGs identified in soybean seedlings treated with fluopyram are linked to systemic resistance, suggesting a potential role of systemic resistance in the suppression of SCN by fluopyram, in addition to the known nematicidal activity. The non-target inhibition of soybean succinate dehydrogenase genes by fluopyram may be the origin of the phytotoxicity symptoms observed and potentially the source of the systemic resistance activation reported in the current study. This work helps to elucidate the mechanisms of suppression of SCN by fluopyram.

Reduction of Pythium Damping-Off in Soybean by Biocontrol Seed Treatment.

Pythium spp. is one of the major groups of pathogens that cause seedling diseases on soybean, leading to both preemergence and postemergence damping-off and root rot. More than 100 species have been identified within this genus, with Pythium irregulare, P. sylvaticum, P. ultimum var ultimum, and P. torulosum being particularly important for soybean production given their aggressiveness, prevalence, and abundance in production fields. This study investigated the antagonistic activity of potential biological control agents (BCAs) native to the U.S. Midwest against Pythium spp. First, in vitro screening identified BCAs that inhibit P. ultimum var. ultimum growth. Scanning electron microscopy demonstrated evidence of mycoparasitism of all potential biocontrol isolates against P. ultimum var. ultimum and P. torulosum, with the formation of appressorium-like structures, short hyphal branches around host hyphae, hook-shaped structures, coiling, and parallel growth of the mycoparasite along the host hyphae. Based on these promising results, selected BCAs were tested under field conditions against six different Pythium spp. Trichoderma afroharzianum 26 used alone and a mix of T. hamatum 16 + T. afroharzianum 19 used as seed treatments protected soybean seedlings from Pythium spp. infection, as BCA-treated plots had on average 15 to 20% greater plant stand and vigor than control plots. Our results also indicate that some of these potential BCAs could be added with a fungicide seed treatment with minimum inhibition occurring, depending on the fungicide active ingredient. This research highlights the need to develop tools incorporating biological control as a facet of soybean seedling disease management programs. The harnessing of native BCAs could be integrated with other management strategies to provide efficient control of seedling diseases.

Microbial Communities Associated With Long-Term Tillage and Fertility Treatments in a Corn-Soybean Cropping System.

Tillage and fertilization are common practices used to enhance soil fertility and increase yield. Changes in soil edaphic properties associated with different tillage and fertility regimes have been widely examined, yet, the microbially mediated pathways and ecological niches involved in enhancing soil fertility are poorly understood. The effects of long-term conventional tillage and no-till in parallel with three fertility treatments (No fertilization, N-only, and NPK) on soil microbial communities were investigated in a long-term field study that was established in the 1970's. Here, we used high-throughput sequencing of bacterial, fungal and oomycetes markers, followed by community-level functional and ecological assembly to discern principles governing tillage and fertility practices' influence on associated soil microbiomes. Both tillage and fertilizer significantly altered microbial community structure, but the tillage effect was more prominent than the fertilizer effect. Tillage significantly affected bacteria, fungi, fusaria, and oomycete beta-diversity, whereas fertilizer only affected bacteria and fungi beta-diversity. In our study different tillage and fertilizer regimes favored specific networks of metabolic pathways and distinct ecological guilds. No-till selected for beneficial microbes that translocate nutrients and resources and protect the host against pathogens. Notably, ecological guilds featuring arbuscular mycorrhizae, mycoparasites, and nematophagous fungi were favored in no-till soils, while fungal saprotrophs and plant pathogens dominated in tilled soils. Conventional till and fertilizer management shifted the communities toward fast growing competitors. Copiotrophic bacteria and fusarium species were favored under conventional tillage and in the presence of fertilizers. The analysis of the metagenomes revealed a higher abundance of predicted pathways associated with energy metabolism, translation, metabolism of cofactors and vitamins, glycan biosynthesis and nucleotide metabolism in no-till. Furthermore, no specific pathways were found to be enriched under the investigated fertilization regimes. Understanding how tillage and fertilizer management shift microbial diversity, structure and ecological niches, such as presented here, can assist with designing farming systems that can maintain high crop yield, while reducing soil erosion and nutrient losses.

Trichoderma Isolates Inhibit Fusarium virguliforme Growth, Reduce Root Rot, and Induce Defense-Related Genes on Soybean Seedlings.

Sudden death syndrome (SDS) caused by Fusarium virguliforme is among the most important diseases affecting soybean in the United States. The use of biological control agents (BCAs) such as Trichoderma spp. can be a valuable resource to suppress F. virguliforme populations. Therefore, this research focused on screening possible BCAs against F. virguliforme and evaluating mycoparasitism and the induction of systemic resistance as mechanisms underlying the antagonistic activity of selected BCAs against F. virguliforme. In total, 47 potential BCAs, including 41 Trichoderma isolates and 6 Mortierella isolates, were screened in a dual-plate assay. The most effective isolates belonged to the Trichoderma harzianum species and were able to inhibit F. virguliforme radial growth by up to 92%. Selected Trichoderma isolates were tested in the greenhouse and in a microplot study. They reduced root rot caused by F. virguliforme when the plants were coinoculated with the pathogen and the BCA. The tested BCA's ability to reduce F. virguliforme growth may be related to several mechanisms of action, including mycoparasitism and induction of defense-related genes in plants, as revealed by monitoring the expression of defense-related genes in soybean. Our results highlight the potential of native Trichoderma isolates to inhibit F. virguliforme growth and reduce SDS severity, providing the basis for future implementation of biological control in soybean production. More efforts are needed to implement the use of these approaches in production fields, and to deepen the current knowledge on the biology of these highly antagonistic isolates.

Tobacco smoking and alcohol drinking among HIV infected people using antiretroviral therapy.

INTRODUCTION: Tobacco smoking, common in people living with human immunodeficiency virus (HIV), is associated with increased mortality and morbidity. This study aimed to determine the proportion of current smokers, as well as assess the factors associated with tobacco smoking and drinking alcohol, among people living with HIV (PLHIV) in Nepal. METHODS: A cross-sectional study was conducted at an antiretroviral therapy (ART) clinic in Kathmandu, Nepal between September and December 2014. Data were collected among 132 HIV infected individuals using a random sampling technique and face-to-face interview. Binary logistic regression analysis was performed to estimate the factors associated with current tobacco smoking and drinking of alcohol. RESULTS: Among the HIV infected people, the proportion of current tobacco smoking was 26.5% (95% Confidence Interval (CI): 18.9-34.1), while drinking of alcohol was 22.7% (95% CI: 15.5-30.0). The respondents who were infected with HIV, after sexual contact with sex workers, were more likely to smoke tobacco (OR=15.2, 95% CI: 4.35-53.08) and drink alcohol (OR=4.50, 95% CI: 1.70-11.93) than those who were infected from drug needle use and blood transfusion. HIV infected individuals, who forgot to take ART medication, were three times more likely (OR=3.17, 95% CI: 1.36-7.38) to drink alcohol than those who did not forget to take ART medication. CONCLUSIONS: Proportion of people who smoke tobacco and drink alcohol is high among the HIV infected individuals who had sexual contact with sex workers in Nepal. There is an urgent need to develop immediate, sustainable and efficient programs to control tobacco smoking and alcohol drinking among vulnerable populations in low and middle-income countries like Nepal. ABBREVIATIONS: HIV: Human Immunodeficiency Virus, AIDS: Acquired Immunodeficiency Syndrome, ART: Antiretroviral Therapy, PLHIV: People Living with Human Immunodeficiency Virus, CI: Confidence Interval, STIDH: Sukraraj Tropical and Infectious Disease Hospital, OR: Odds Ratio, SD: Standard Deviation.