Effect of Soil Biochar Amendment on Wheat Resistance to Fusarium Head Blight and Mycotoxin Contamination

Martha Vaughan - Research Molecular Biologist at the USDA-ARS in Peoria, IL. Mycotoxin contamination of food and feed is among the top food safety concerns. Fusarium head blight (FHB) is one of the most important diseases of wheat and other cereal grains. Fusarium graminearum, the fungal pathogen responsible for FHB, reduces crop yield and results in contamination of grain with carcinogenic mycotoxins called trichothecenes. F. graminearum like other Fusarium spp. efficiently colonizes field crop residues such as wheat stubble and maize stalks. These pathogen reservoirs are primary sources of inoculum for FHB epidemics in wheat. Soil amendment with biochar can confer multiple benefits to plants including increased productivity and enhanced stress resistance. The objective of this study was to test whether biochar could enhance wheat resistance to F. graminearum disease severity and trichothecene contamination. Because biochar has also been shown to promote the growth of beneficial microorganisms within the rhizosphere, we further assessed the potential of biochar as a carrier system for applying the biocontrol agent Trichoderma harzianum which is known to be effective against several fungal soil-borne plant pathogens including F. graminearum.Ope

An aeroponic culture system for the study of root herbivory on Arabidopsis thaliana

<p>Abstract</p> <p>Background</p> <p>Plant defense against herbivory has been studied primarily in aerial tissues. However, complex defense mechanisms have evolved in all parts of the plant to combat herbivore attack and these mechanisms are likely to differ in the aerial and subterranean environment. Research investigating defense responses belowground has been hindered by experimental difficulties associated with the accessibility and quality of root tissue and the lack of bioassays using model plants with altered defense profiles.</p> <p>Results</p> <p>We have developed an aeroponic culture system based on a calcined clay substrate that allows insect herbivores to feed on plant roots while providing easy recovery of the root tissue. The culture method was validated by a root-herbivore system developed for <it>Arabidopsis thaliana </it>and the herbivore <it>Bradysia </it>spp. (fungus gnat)<it>. Arabidopsis </it>root mass obtained from aeroponically grown plants was comparable to that from other culture systems, and the plants were morphologically normal. <it>Bradysia </it>larvae caused considerable root damage resulting in reduced root biomass and water absorption. After feeding on the aeroponically grown root tissue, the larvae pupated and emerged as adults. Root damage of mature plants cultivated in aeroponic substrate was compared to that of <it>Arabidopsis </it>seedlings grown in potting mix. Seedlings were notably more susceptible to <it>Bradysia </it>feeding than mature plants and showed decreased overall growth and survival rates.</p> <p>Conclusions</p> <p>A root-herbivore system consisting of <it>Arabidopsis thaliana </it>and larvae of the opportunistic herbivore <it>Bradysia </it>spp. has been established that mimics herbivory in the rhizosphere. <it>Bradysia </it>infestation of <it>Arabidopsis </it>grown in this culture system significantly affects plant performance. The culture method will allow simple profiling and <it>in vivo </it>functional analysis of root defenses such as chemical defense metabolites that are released in response to belowground insect attack.</p

Understanding adolescent girls\u27 protection strategies against HIV: An exploratory study in urban Lusaka

This report provides a descriptive analysis of how adolescent girls and young women in Lusaka, Zambia construct notions of risk and safety, perceive reproductive health and HIV risks, and identify behaviors and actions they can take to protect themselves. Findings suggests stronger social support networks, improved access to the range of reproductive health services and products, and safe and supportive spaces for girls would be beneficial. The report points to several areas for potential program attention, including more focused attention on the structural and environmental drivers of girls’ vulnerability

Effects of elevated [CO2 ] on maize defence against mycotoxigenic Fusarium verticillioides.

Maize is by quantity the most important C4 cereal crop; however, future climate changes are expected to increase maize susceptibility to mycotoxigenic fungal pathogens and reduce productivity. While rising atmospheric [CO2 ] is a driving force behind the warmer temperatures and drought, which aggravate fungal disease and mycotoxin accumulation, our understanding of how elevated [CO2 ] will effect maize defences against such pathogens is limited. Here we report that elevated [CO2 ] increases maize susceptibility to Fusarium verticillioides proliferation, while mycotoxin levels are unaltered. Fumonisin production is not proportional to the increase in F. verticillioides biomass, and the amount of fumonisin produced per unit pathogen is reduced at elevated [CO2 ]. Following F. verticillioides stalk inoculation, the accumulation of sugars, free fatty acids, lipoxygenase (LOX) transcripts, phytohormones and downstream phytoalexins is dampened in maize grown at elevated [CO2 ]. The attenuation of maize 13-LOXs and jasmonic acid production correlates with reduced terpenoid phytoalexins and increased susceptibility. Furthermore, the attenuated induction of 9-LOXs, which have been suggested to stimulate mycotoxin biosynthesis, is consistent with reduced fumonisin per unit fungal biomass at elevated [CO2 ]. Our findings suggest that elevated [CO2 ] will compromise maize LOX-dependent signalling, which will influence the interactions between maize and mycotoxigenic fungi

Climate change impacts on the ecology of 'Fusarium graminearum' species complex and susceptibility of wheat to 'Fusarium' head blight: a review

'Fusarium' head blight (FHB) of wheat, caused mainly by a few members of the 'Fusarium graminearum' species complex (FGSC), is a major threat to agricultural grain production, food safety, and animal health. The severity of disease epidemics and accumulation of associated trichothecene mycotoxins in wheat kernels is strongly driven by meteorological factors. The potential impacts of change in climate are reviewed from the perspective of the FGSC life cycle and host resistance mechanisms influenced by abiotic pressures at the ecological, physiological and molecular level. Alterations in climate patterns and cropping systems may affect the distribution, composition and load of FGSC inoculum, but quantitative information is lacking regarding the differential responses among FGSC members. In general, the coincidence of wet and warm environment during flowering enhances the risk of FHB epidemics, but the magnitude and direction of the change in FHB and mycotoxin risk will be a consequence of a multitude of effects on key processes affecting inoculum dynamics and host susceptibility. Rates of residue decomposition, inoculum production and dispersal may be significantly altered by changes in crop rotations, atmospheric carbon dioxide concentration ([CO₂]), temperature and precipitation patterns, but the impact may be much greater for regions where inoculum is more limited, such as temperate climates. In regions of non-limiting inoculum, climate change effects will likely be greater on the pathogenic rather than on the saprophytic phase. Although the mechanisms by which abiotic stress influences wheat defences against 'Fusarium' species are unknown, available data would suggest that wheat may be more susceptible to 'Fusarium' infection under future climate conditions. Additional research in this area should be a priority so that breeding efforts and climate resilient management strategies can be developed

Effects of Atmospheric CO2 Level on the Metabolic Response of Resistant and Susceptible Wheat to Fusarium graminearum Infection.

Rising atmospheric CO2 concentrations and associated climate changes are thought to have contributed to the steady increase of Fusarium head blight (FHB) on wheat. However, our understanding of precisely how elevated CO2 influences the defense response of wheat against Fusarium graminearum remains limited. In this study, we evaluated the metabolic profiles of susceptible (Norm) and moderately resistant (Alsen) spring wheat in response to whole-head inoculation with two deoxynivalenol (DON)-producing F. graminearum isolates (DON+), isolates 9F1 and Gz3639, and a DON-deficient (DON−) isolate (Gzt40) at ambient (400 ppm) and elevated (800 ppm) CO2 concentrations. The effects of elevated CO2 were dependent on both the Fusarium strain and the wheat variety, but metabolic differences in the host can explain the observed changes in F. graminearum biomass and DON accumulation. The complexity of abiotic and biotic stress interactions makes it difficult to determine if the observed metabolic changes in wheat are a result of CO2-induced changes in the host, the pathogen, or a combination of both. However, the effects of elevated CO2 were not dependent on DON production. Finally, we identified several metabolic biomarkers for wheat that can reliably predict FHB resistance or susceptibility, even as atmospheric CO2 levels rise

Characterization of a Fusarium graminearum Salicylate Hydroxylase

Salicylic acid (SA) plays an important role in regulating plant defense responses against pathogens. However, pathogens have evolved ways to manipulate plant SA-mediated defense signaling. Fusarium graminearum causes Fusarium head blight (FHB) and reduces crop yields and quality by producing various mycotoxins. In this study, we aimed to identify the salicylate hydroxylase in F. graminearum and determine its role in wheat head blight development. We initially identified a gene in F. graminearum strain NRRL 46422 that encodes a putative salicylate hydroxylase (designated FgShyC). However, the FgShyC deletion mutant showed a similar ability to degrade SA as wild-type strain 46422; nor did overexpression of FgShyC in E. coli convert SA to catechol. The results indicate that FgShyC is not involved in SA degradation. Further genome sequence analyses resulted in the identification of eight salicylate hydroxylase candidates. Upon addition of 1 mM SA, FGSG_03657 (designated FgShy1), was induced approximately 400-fold. Heterologous expression of FgShy1 in E. coli converted SA to catechol, confirming that FgShy1 is a salicylate hydroxylase. Deletion mutants of FgShy1 were greatly impaired but not completely blocked in SA degradation. Expression analyses of infected tissue showed that FgShy1 was induced during infection, but virulence assays revealed that deletion of FgShy1 alone was not sufficient to affect FHB severity. Although the Fgshy1 deletion mutant did not reduce pathogenicity, we cannot rule out that additional salicylate hydroxylases are present in F. graminearum and characterization of these enzymes will be necessary to fully understand the role of SA-degradation in FHB pathogenesis

Evolution of structural diversity of trichothecenes, a family of toxins produced by plant pathogenic and entomopathogenic fungi

[EN] Trichothecenes are a family of terpenoid toxins produced by multiple genera of fungi, including plant and insect pathogens. Some trichothecenes produced by the fungus Fusarium are among the mycotoxins of greatest concern to food and feed safety because of their toxicity and frequent occurrence in cereal crops, and trichothecene production contributes to pathogenesis of some Fusarium species on plants. Collectively, fungi produce over 150 trichothecene analogs: i.e., molecules that share the same core structure but differ in patterns of substituents attached to the core structure. Here, we carried out genomic, phylogenetic, gene-function, and analytical chemistry studies of strains from nine fungal genera to identify genetic variation responsible for trichothecene structural diversity and to gain insight into evolutionary processes that have contributed to the variation. The results indicate that structural diversity has resulted from gain, loss, and functional changes of trichothecene biosynthetic (TRI) genes. The results also indicate that the presence of some substituents has arisen independently in different fungi by gain of different genes with the same function. Variation in TRI gene duplication and number of TRI loci was also observed among the fungi examined, but there was no evidence that such genetic differences have contributed to trichothecene structural variation. We also inferred ancestral states of the TRI cluster and trichothecene biosynthetic pathway, and proposed scenarios for changes in trichothecene structures during divergence of TRI cluster homologs. Together, our findings provide insight into evolutionary processes responsible for structural diversification of toxins produced by pathogenic fungiSISG received funding from the Spanish Ministry of Economy and Competitiveness (grant number MINECO-AGL2015-70671-C2-2-R). TL received funding from the National Institute of Agricultural Sciences, Rural Development Administration (grant number PJ00843203). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscrip

Generation of Alkalinity by Stimulation of Microbial Iron Reduction in Acid Rock Drainage Systems: Impact of Natural Organic Matter Types

From Springer Nature via Jisc Publications RouterHistory: received 2020-04-08, accepted 2020-08-13, registration 2020-08-14, pub-electronic 2020-08-31, online 2020-08-31, pub-print 2020-09Publication status: PublishedFunder: CONACyT-Mexico; Grant(s): 308702Abstract: To determine the role of organic matter in the attenuation of acid rock drainage (ARD), microcosm-based experiments were performed using ARD stimulated with plants and manures. Initial mineralogical, organic geochemical and microbial analyses indicated a predominance of goethite, a substantial amount of organic carbon originating from local sources, and a bacterial community comparable with those detected in a range of ARD sites worldwide. After 100 days of incubation, changes in the mineralogical, organic and microbiological composition of the ARD demonstrated that the plant additions stimulate microbes with the potential to degrade this organic matter but do not necessarily cause substantial Fe(III) reduction. Conversely, the greatest observed stimulation of Fe(III) reduction, associated with an increase in pH to near-neutral values, was observed using manure additions. These results demonstrate that the use of the optimal natural carbon source is important and can promote the metabolism of microorganisms potentially fuelling a range of geomicrobial processes, including iron and sulfate reduction

Peat Bog Wildfire Smoke Exposure in Rural North Carolina Is Associated with Cardiopulmonary Emergency Department Visits Assessed through Syndromic Surveillance

Background: In June 2008, burning peat deposits produced haze and air pollution far in excess of National Ambient Air Quality Standards, encroaching on rural communities of eastern North Carolina. Although the association of mortality and morbidity with exposure to urban air pollution is well established, the health effects associated with exposure to wildfire emissions are less well understood. Objective: We investigated the effects of exposure on cardiorespiratory outcomes in the population affected by the fire. Methods: We performed a population-based study using emergency department (ED) visits reported through the syndromic surveillance program NC DETECT (North Carolina Disease Event Tracking and Epidemiologic Collection Tool). We used aerosol optical depth measured by a satellite to determine a high-exposure window and distinguish counties most impacted by the dense smoke plume from surrounding referent counties. Poisson log-linear regression with a 5-day distributed lag was used to estimate changes in the cumulative relative risk (RR). Results: In the exposed counties, significant increases in cumulative RR for asthma [1.65 (95% confidence interval, 1.25–2.1)], chronic obstructive pulmonary disease [1.73 (1.06–2.83)], and pneumonia and acute bronchitis [1.59 (1.07–2.34)] were observed. ED visits associated with cardiopulmonary symptoms [1.23 (1.06–1.43)] and heart failure [1.37 (1.01–1.85)] were also significantly increased. Conclusions: Satellite data and syndromic surveillance were combined to assess the health impacts of wildfire smoke in rural counties with sparse air-quality monitoring. This is the first study to demonstrate both respiratory and cardiac effects after brief exposure to peat wildfire smoke