Fusarium head blight (FHB) is a fungal disease that affects cereals and is capable of producing mycotoxins, creating health concerns. In southern Brazil, FHB of wheat is caused by the Fusarium ...graminearum species complex that produces mainly deoxynivalenol (DON) and zearalenone (ZON) mycotoxins. There is a need for research-based information on how different contamination levels affect these mycotoxins' distribution in the milling process. The objective of this study was to analyze the Fusarium mycotoxin distribution within each milled fraction, extracted from wheat lots artificially contaminated with a crescent gradient of mycotoxins. Wheat samples produced in 2013 season in Southern Brazil region were obtained from plots of breeding program. The wheat samples were artificially contaminated with residues of cleaning and pre-cleaning process, including light and shriveled grains, obtained from a Fusarium nursery screening plot. Pilot-scale milled wheat fractions were collected, comprising finished flour and bran. The Fusarium mycotoxin content was determined by chromatography (UHPLC-MS/MS). The results obtained show that DON presented exponential growth relative to the initial levels of mycotoxin in wheat milled fractions (finished flour and bran). The DON concentration was significativelly higher in bran, when compared with milled wheat and finished flour, in the DON levels lower than 1000 μg kg−1. The finished flour presented lower DON levels when compared with milled wheat, but this reduction was inadequate, to meet the current regulation limits for food.
•Milled fractions presented exponential growth of DON relative to the initial levels.•DON levels increased significantly in bran in the lower levels, up to 1000 μg kg−1.•The mycotoxin in the internal part of the grain was likely due to fungal growth.•Milling process cannot be solely used as an effective tool for DON reduction.
Originating in South America, wheat blast disease has spread to both Asia and Africa and is considered a significant threat to food security. Bangladesh experienced the first outbreak of wheat blast ...outside of the Americas in 2016. Shortly thereafter, the blast-resistant variety BARI Gom 33 was released. Seeds of this variety are however not as widely available as required, although the disease threat remains. While varietal mixtures have been shown to mitigate some symptoms and yield losses associated with other fungal diseases in wheat, there is a complete research gap on this topic as it pertains to wheat blast. As such, we evaluated the potential of using BARI Gom 33 as a component of a variety mixture under high disease pressure in Bangladesh. During three cropping seasons, blast symptoms and yield were determined in a field experiment for the highly blast-susceptible variety BARI Gom 26, the moderately susceptible BARI Gom 30, the resistant BARI Gom 33, and seven mixture combinations of the three varieties using artificial inoculation to increase disease pressure. In addition to wheat blast, Bipolaris leaf blight (BpLB) symptoms were observed and evaluated. While yields of the susceptible varieties were severely affected by blast even after fungicide application, disease-inflicted yield loss without fungicide was only 15% for sole BARI Gom 33 and did not differ significantly from yield losses in BARI Gom 33 and BARI Gom 30 mixtures. Furthermore, in the mixture containing 67% BARI Gom 33 and 33% BARI Gom 30, blast incidence and severity were reduced by 25% and 16%, respectively, in comparison to weighted values in sole stands. Conversely, mixing varieties tended to increase the symptoms of BpLB. Under high wheat blast pressure, fungicide protection against blast was relatively weak, underscoring the importance of resistant varieties. Although variety mixtures did not increase yield, the yield advantage of BARI Gom 33 was maintained when its seeds were mixed with the less resistant BARI Gom 30. This study confirms recommendations that farmers should use BARI Gom 33 as a first line of defense against wheat blast in Bangladesh. Yet where farmers cannot access sufficient BARI Gom 33 seed for planting, our data suggest that agricultural extension services can recommend this variety with non-resistant cultivars as interim strategy without significant risk of yield loss.
•Wheat blast globally threatens, expanding in Bangladesh despite the release of blast-resistant BARI Gom 33.•Limited availability of resistant variety led to a study mixing it with susceptible varieties under high disease pressure.•Mixing BARI Gom 30 with BARI Gom 33 seeds showed promising loss mitigation.•Fungicide controlled BpLB effectively but struggled against blast.•Using BARI Gom 33 in mixtures addresses wheat blast amid seed challenges in Bangladesh.
Wheat blast, caused by Magnaporthe oryzae Triticum (MoT) pathotype, is a global threat to wheat (Triticum aestivum L.) production. Few blast resistance (R) genes have been identified to date, ...therefore assessing potential sources of resistance in wheat is important. The Brazilian wheat cultivar BR 18-Terena is considered one of the best sources of resistance to blast and has been widely used in Brazilian breeding programmes, however the underlying genetics of this resistance are unknown.
BR 18-Terena was used as the common parent in the development of two recombinant inbred line (RIL) F
populations with the Brazilian cultivars Anahuac 75 and BRS 179. Populations were phenotyped for resistance at the seedling and heading stage using the sequenced MoT isolate BR32, with transgressive segregation being observed. Genetic maps containing 1779 and 1318 markers, were produced for the Anahuac 75 × BR 18-Terena and BR 18-Terena × BRS 179 populations, respectively. Five quantitative trait loci (QTL) associated with seedling resistance, on chromosomes 2B, 4B (2 QTL), 5A and 6A, were identified, as were four QTL associated with heading stage resistance (1A, 2B, 4A and 5A). Seedling and heading stage QTL did not co-locate, despite a significant positive correlation between these traits, indicating that resistance at these developmental stages is likely to be controlled by different genes. BR 18-Terena provided the resistant allele for six QTL, at both developmental stages, with the largest phenotypic effect conferred by a QTL being 24.8% suggesting that BR 18-Terena possesses quantitative resistance. Haplotype analysis of 100 Brazilian wheat cultivars indicates that 11.0% of cultivars already possess a BR 18-Terena-like haplotype for more than one of the identified heading stage QTL.
This study suggests that BR 18-Terena possesses quantitative resistance to wheat blast, with nine QTL associated with resistance at either the seedling or heading stage being detected. Wheat blast resistance is also largely tissue-specific. Identification of durable quantitative resistances which can be combined with race-specific R gene-mediated resistance is critical to effectively control wheat blast. Collectively, this work facilitates marker-assisted selection to develop new varieties for cultivation in regions at risk from this emerging disease.
Fusarium head blight (FHB) is a disease of wheat (Triticum aestivum L.) that causes major yield losses in South America, as well as many other wheat growing regions around the world. FHB results in ...low quality, contaminated grain due to the production of mycotoxins such as deoxynivalenol (DON). In Brazil, FHB outbreaks are increasing in frequency and are currently controlled by fungicides which are costly and potentially harmful to the wider environment. To identify the genetic basis of resistance to FHB in Brazilian wheat, two mapping populations (Anahuac 75 × BR 18-Terena and BR 18-Terena × BRS 179) segregating for FHB resistance were phenotyped and quantitative trait loci (QTL) analysis was undertaken to identify genomic regions associated with FHB-related traits. A total of 14 QTL associated with FHB visual symptoms were identified, each of which explained 3.7-17.3% of the phenotypic variance. Two of these QTL were stable across environments. This suggests FHB resistance in Anahuac 75, BR 18-Terena and BRS 179 is controlled by multiple genetic loci that confer relatively minor differences in resistance. A major, novel QTL associated with DON accumulation was also identified on chromosome 4B (17.8% of the phenotypic variance), as well as a major QTL associated with thousand-grain weight on chromosome 6B (16.8% phenotypic variance). These QTL could be useful breeding targets, when pyramided with major sources of resistance such as Fhb1, to improve grain quality and reduce the reliance on fungicides in Brazil and other countries affected by FHB.
Mycotoxins are a ubiquitous contaminant and are difficult to prevent or to diminish; it is, therefore, important to establish the contributions of processing steps to eliminating mycotoxins in the ...production of safer foods. The objective of this study was to investigate the effects of wheat cleaning, sorting, and milling processes on Fusarium mycotoxin distribution in two naturally contaminated wheat cultivars. The study focused on evaluating the effects of first-stage processing methods, cleaning, and gravity separator, on wheat mycotoxin content. The distribution of Fusarium mycotoxins was analyzed after two milling processes. Firstly, a Laboratory Mill 3100 was used to obtain the whole milled wheat. Secondly, a pilot-scale mill Quadrumat Senior was used to get wheat milled fractions (finished flour and bran). Wheat samples (BRS Parrudo and BRS 374) were collected during the 2014 season that were highly vulnerable to Fusarium outbreaks in Southern Brazil. Fusarium toxin (DON, 3-ADON, 15-ADON, NIV, and ZON) levels were determined for all milled fractions via chromatography (UHPLC-MS/MS). The cleaning and sorting methods employed post-harvest significantly reduced the mycotoxin content in wheat. The reduction of mycotoxin was progressive through each processing method, and the gravity separator equipment resulted in the lowest contamination levels in products intended for human consumption for both cultivars. Through the milling process, the DON contamination in finished flour was significantly lower than in milled wheat; however, there were no significant differences in contamination between the milled wheat and bran. The cleaning and sorting methods for both wheat cultivars generated safer foods when compared with unsorted wheat samples (BRS Parrudo and BRS 374).
•Cleaning and sorting methods significantly reduced the mycotoxin content in wheat.•Gravity separator resulted in the lower contamination levels in wheat by-products.•Through the milling, DON levels were reduced significantly in finished flour.•FHB susceptible cultivar accumulated twice as much DON as the moderately resistant.
Wheat blast caused by
Magnaporthe oryzae
is a relatively new disease that has caused considerable losses in wheat fields of several South American countries, including Brazil. The 2016 report of ...wheat blast occurrence in Bangladesh raised concern in South Asia where wheat represents a significant crop. The sources of primary inoculum and survival from season to season of the fungus remain largely unknown. The effect of wheat residues on the onset of blast epidemics and the potential for survival of
M. oryzae
in the residues were studied under subtropical climatic conditions, in the South of Brazil. The objective of this study was to monitor the saprotrophic development of
M. oryzae
on wheat debris and explore the relative importance of crop residues as a source of inoculum. The wheat cultivars BRS 229 and Anahuac 75, moderately and highly susceptible to the disease, respectively, were inoculated with a spore suspension of 10
−5
conidia mL
−1
using an aggressive (
Py
12.1.209) and a less aggressive (
Py
12.1.132) isolate. At maturity, a portion of leaves, stems and spikes were detached from plants, and a group of ten lesions were randomly selected and marked on each type of plant organ. The air-dried plant organs were placed separately inside bags and exposed outside. The experiment was conducted over three different time intervals. Each 14 days, samples were taken from the field and tested for sporulation. The survival of the blast fungus decreased rapidly on the rachis when compared to stems and leaves. Sporulation of the fungus was observed on the wheat residues for up to five months. Based on the results of this study, the possibility that the causal agent of wheat blast survives under Brazilian conditions from one crop to another in wheat residues is very low. The management of crop residues is not a key point to control the development of wheat blast. A strong emphasis should be placed on the presence of other hosts.
Abstract The objective of this work was to evaluate the use of the surface moisture data generated by the temperature-vegetation dryness index (TVDI), obtained from sensors positioned on the surface ...of a soybean (Glycine max) agricultural field. The dry and wet limits of the index were obtained using Landsat-8 images covering the region around the crop. To assess the quality and consistency of the TVDI, a correlation analysis was carried out between the TVDI, the normalized difference vegetation index (NDVI), surface temperature (TS), and the variables that are usually used to express surface moisture. The TVDI showed a significant correlation with soil moisture, water storage in the soil, water deficit, real evapotranspiration, and the real evapotranspiration/potential evapotranspiration ratio. The displacement of radiometric data measured on the surface (NDVI and TS) within the evaporative triangle, adjusted with orbital data, consistently describes the variability of water conditions during the study period, being a tool to support decision-making in crop management.
Resumo O objetivo deste trabalho foi avaliar o uso dos dados de umidade da superfície gerados pelo índice “temperature-vegetation dryness index” (TVDI), obtido de sensores posicionados na superfície de uma área agrícola de soja (Glycine max). Os limites seco e úmido do índice foram obtidos com uso de imagens Landsat-8 que abrangem a região em torno da lavoura. Para avaliar a qualidade e a coerência do TVDI, foi realizada análise de correlação entre o TVDI, o “normalized difference vegetation index” (NDVI), a temperatura da superfície (TS), e as variáveis usualmente utilizadas para expressar a umidade da superfície. O TVDI mostrou correlação significativa com umidade do solo, armazenamento de água no solo, deficit hídrico, evapotranspiração real e relação evapotranspiração real/evapotranspiração potencial. O deslocamento dos dados radiométricos medidos na superfície (NDVI e TS) dentro do triângulo evaporativo, ajustado com dados orbitais, descreve de forma consistente a variabilidade das condições hídricas no período de estudo, sendo uma ferramenta para apoio à tomada de decisões no manejo de culturas.
Abstract
Background
Disease suppressiveness of soils to fungal root pathogens is typically induced in the field by repeated infections of the host plant and concomitant changes in the taxonomic ...composition and functional traits of the rhizosphere microbiome. Here, we studied this remarkable phenomenon for
Bipolaris sorokiniana
in two wheat cultivars differing in resistance to this fungal root pathogen.
Results
The results showed that repeated exposure of the susceptible wheat cultivar to the pathogen led to a significant reduction in disease severity after five successive growth cycles. Surprisingly, the resistant wheat cultivar, initially included as a control, showed the opposite pattern with an increase in disease severity after repeated pathogen exposure. Amplicon analyses revealed that the bacterial families
Chitinophagaceae
,
Anaerolineaceae
and
Nitrosomonadaceae
were associated with disease suppressiveness in the susceptible wheat cultivar; disease suppressiveness in the resistant wheat cultivar was also associated with
Chitinophagaceae
and a higher abundance of
Comamonadaceae
. Metagenome analysis led to the selection of 604 Biosynthetic Gene Clusters (BGCs), out of a total of 2,571 identified by AntiSMASH analysis, that were overrepresented when the soil entered the disease suppressive state. These BGCs are involved in the biosynthesis of terpenes, non-ribosomal peptides, polyketides, aryl polyenes and post-translationally modified peptides.
Conclusion
Combining taxonomic and functional profiling we identified key changes in the rhizosphere microbiome during disease suppression. This illustrates how the host plant relies on the rhizosphere microbiome as the first line of defense to fight soil-borne pathogens. Microbial taxa and functions identified here can be used in novel strategies to control soil-borne fungal pathogens.
No Rio Grande do Sul são poucos os fragmentos de Floresta Ombrófila Mista em estado natural. Isso, por si só, justifica a importância de estudar esses locais visando à compreensão da sua dinâmica ...interna e da sua relação com o ambiente de entorno. O objetivo deste trabalho foi caracterizar o crescimento e acúmulo de biomassa de um remanescente de Floresta Ombrófila Mista, localizado na Floresta Nacional de Passo Fundo (FLONA). O experimento foi realizado no Município de Mato Castelhano, RS, utilizando o método de área fixa. Foram instaladas 10 parcelas com 30 x 30 m (900 m²), totalizando 9.000 m², em outubro de 2009. Todas as árvores com Diâmetro à Altura do Peito (DAP) maior que 0,1 m foram identificadas. Nos anos 2009, 2010 e 2012, os indivíduos marcados foram contados e seus DAP, medidos. Com os resultados do DAP das árvores, foram realizados o cálculo da área basal e a estimativa da biomassa da vegetação. O total de indivíduos amostrados foi de 402 (447 árvores ha-1). O diâmetro médio das árvores foi de 0,270 m e a área basal das árvores remanescentes, de 35,58; 36,19; e 37,47 m² ha-1, respectivamente nos anos 2009, 2010 e 2012. Esse incremento da área basal no período avaliado resultou em aumento de 217% no valor da biomassa da avaliação de 2009-2010 para 2010-2012. A FLONA de Passo Fundo apresentou aumento no diâmetro das árvores ao longo do tempo, o que resultou em aumento também no acúmulo de biomassa pelo maciço florestal.
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