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1.
J Agric Food Chem ; 68(9): 2607-2614, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32096642

RESUMO

Fused-ring aromatics, important skeletal components of black carbon (BC), contribute to long-term carbon (C) sequestration in nature. They have previously been thought to be primarily formed by incomplete combustion of organic materials, whereas the nonpyrogenic origins are negligible. Using advanced solid-state 13C nuclear magnetic resonance (NMR), including recoupled long-range C-H dipolar dephasing, exchange with protonated and nonprotonated spectral editing (EXPANSE), and dipolar-dephased double-quantum/single-quantum (DQ/SQ) spectroscopy, we for the first time identify fused-ring aromatics that formed during the decomposition of wheat (Triticum sp.) straw in soil under aerobic, but not anaerobic conditions. The observed formation of polyaromatic units as plant litter decomposes provides direct evidence for humification. Moreover, the estimation of the annual flux of such nonpyrogenic BC could be equivalent to 3-12% of pyrogenic BC added to soils from all other sources. Our findings significantly extend the understanding of potential sources of fused-ring aromatic C and BC in soils as well as the global C cycle.


Assuntos
Triticum/química , Aerobiose , Bactérias/metabolismo , Biodegradação Ambiental , Caules de Planta/química , Caules de Planta/microbiologia , Microbiologia do Solo , Triticum/microbiologia
2.
Food Microbiol ; 87: 103380, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31948621

RESUMO

Wheat flour has recently been recognised as an exposure vehicle for the foodborne pathogen Shiga toxin-producing Escherichia coli (STEC). Wheat flour milled on two sequential production days in October 2016, and implicated in a Canada wide outbreak of STEC O121:H19, was analysed for the presence of STEC in November 2018. Stored in sealed containers at ambient temperature, the water activity of individual flour samples was below 0.5 at 6 months post-milling and remained static or decreased slightly in individual samples during 18 months of additional storage. STEC O121 was isolated, with the same genotype (stx2a, eae, hlyA) and core genome multilocus sequence type as previous flour and clinical isolates associated with the outbreak. The result of this analysis demonstrates the potential for STEC to persist in wheat flour at levels associated with outbreak infections for periods of up to two years. This has implications for the potential for STEC to survive in other foods with low water activity.


Assuntos
Farinha/microbiologia , Escherichia coli Shiga Toxigênica/crescimento & desenvolvimento , Triticum/microbiologia , Contaminação de Alimentos/análise , Armazenamento de Alimentos , Viabilidade Microbiana , Escherichia coli Shiga Toxigênica/genética , Escherichia coli Shiga Toxigênica/isolamento & purificação
3.
Theor Appl Genet ; 133(3): 785-808, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31996971

RESUMO

KEY MESSAGE: A locus on wheat chromosome 2A was found to control field resistance to both leaf and glume blotch caused by the necrotrophic fungal pathogen Parastagonospora nodorum. The necrotrophic fungal pathogen Parastagonospora nodorum is the causal agent of Septoria nodorum leaf blotch and glume blotch, which are common wheat (Triticum aestivum L.) diseases in humid and temperate areas. Susceptibility to Septoria nodorum leaf blotch can partly be explained by sensitivity to corresponding P. nodorum necrotrophic effectors (NEs). Susceptibility to glume blotch is also quantitative; however, the underlying genetics have not been studied in detail. Here, we genetically map resistance/susceptibility loci to leaf and glume blotch using an eight-founder wheat multiparent advanced generation intercross population. The population was assessed in six field trials across two sites and 4 years. Seedling infiltration and inoculation assays using three P. nodorum isolates were also carried out, in order to compare quantitative trait loci (QTL) identified under controlled conditions with those identified in the field. Three significant field resistance QTL were identified on chromosomes 2A and 6A, while four significant seedling resistance QTL were detected on chromosomes 2D, 5B and 7D. Among these, QSnb.niab-2A.3 for field resistance to both leaf blotch and glume blotch was detected in Norway and the UK. Colocation with a QTL for seedling reactions against culture filtrate from a Norwegian P. nodorum isolate indicated the QTL could be caused by a novel NE sensitivity. The consistency of this QTL for leaf blotch at the seedling and adult plant stages and culture filtrate infiltration was confirmed by haplotype analysis. However, opposite effects for the leaf blotch and glume blotch reactions suggest that different genetic mechanisms may be involved.


Assuntos
Ascomicetos/patogenicidade , Resistência à Doença/genética , Doenças das Plantas/genética , Triticum/genética , Mapeamento Cromossômico , Cromossomos de Plantas , Efeito Fundador , Noruega , Fenótipo , Doenças das Plantas/microbiologia , Folhas de Planta/microbiologia , Locos de Características Quantitativas , Triticum/microbiologia , Reino Unido
4.
Plant Dis ; 104(1): 71-81, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31697221

RESUMO

The ToxA-Tsn1 system is an example of an inverse gene-for-gene relationship. The gene ToxA encodes a host-selective toxin (HST) which functions as a necrotrophic effector and is often responsible for the virulence of the pathogen. The genomes of several fungal pathogens (e.g., Pyrenophora tritici-repentis, Parastagonospora nodorum, and Bipolaris sorokiniana) have been shown to carry the ToxA gene. Tsn1 is a sensitivity gene in the host, whose presence generally helps a ToxA-positive pathogen to cause spot blotch in wheat. Cultivars lacking Tsn1 are generally resistant to spot blotch; this resistance is attributed to a number of other known genes which impart resistance in the absence of Tsn1. In the present study, 110 isolates of B. sorokiniana strains, collected from the ME5A and ME4C megaenvironments of India, were screened for the presence of the ToxA gene; 77 (70%) were found to be ToxA positive. Similarly, 220 Indian wheat cultivars were screened for the presence of the Tsn1 gene; 81 (36.8%) were found to be Tsn1 positive. When 20 wheat cultivars (11 with Tsn1 and 9 with tsn1) were inoculated with ToxA-positive isolates, seedlings of only those carrying the Tsn1 allele (not tsn1) developed necrotic spots surrounded by a chlorotic halo. No such distinction between Tsn1 and tsn1 carriers was observed when adult plants were inoculated. This study suggests that the absence of Tsn1 facilitated resistance against spot blotch of wheat. Therefore, the selection of wheat genotypes for the absence of the Tsn1 allele can improve resistance to spot blotch.


Assuntos
Ascomicetos , Interações Hospedeiro-Patógeno , Triticum , Virulência , Ascomicetos/genética , Ascomicetos/patogenicidade , Resistência à Doença/genética , Genes Fúngicos/genética , Genes de Plantas/genética , Interações Hospedeiro-Patógeno/genética , Índia , Triticum/genética , Triticum/microbiologia , Virulência/genética
5.
Plant Dis ; 104(1): 35-43, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31660799

RESUMO

Wheat head blast (WHB), caused by the fungus Magnaporthe oryzae pathotype triticum, is a devastating disease affecting South America and South Asia. Despite 30 years of intensive effort, the 2NVS translocation from Aegilops ventricosa contains the only useful source of resistance to WHB effective against M. oryzae triticum isolates. The objective of this study was to identify non-2NVS sources of resistance to WHB among elite cultivars, breeding lines, landraces, and wild-relative accessions. Over 780 accessions were evaluated under field and greenhouse conditions in Bolivia, greenhouse conditions in Brazil, and at two biosafety level-3 laboratories in the United States. The M. oryzae triticum isolates B-71 (2012), 008 (2015), and 16MoT001 (2016) were used for controlled experiments, while isolate 008 was used for field experiments. Resistant and susceptible checks were included in all experiments. Under field conditions, susceptible spreaders were inoculated at the tillering stage to guarantee sufficient inoculum. Disease incidence and severity were evaluated as the average rating for each 1-m-row plot. Under controlled conditions, heads were inoculated after full emergence and individually rated for percentage of diseased spikelets. The diagnostic marker Ventriup-LN2 was used to test for the presence of the 2NVS translocation. Four non-2NVS spring wheat International Maize and Wheat Improvement Center breeding lines (CM22, CM49, CM52, and CM61) and four wheat wild-relatives (A. tauschii TA10142, TA1624, TA1667, and TA10140) were identified as resistant (<5% of severity) or moderately resistant (5 to <25% severity) to WHB. Experiments conducted at the seedling stage showed little correlation with disease severity at the head stage. M. oryzae triticum isolate 16MoT001 was significantly more aggressive against 2NVS-based varieties. The low frequency of WHB resistance and the increase in aggressiveness of newer M. oryzae triticum isolates highlight the threat that the disease poses to wheat production worldwide and the urgent need to identify and characterize new resistance genes that can be used in breeding for durably resistant varieties.


Assuntos
Resistência à Doença , Triticum , Ásia , Bolívia , Brasil , Cruzamento , Resistência à Doença/genética , Doenças das Plantas/microbiologia , Triticum/genética , Triticum/microbiologia
6.
Syst Appl Microbiol ; 43(1): 126025, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31704194

RESUMO

The main goal of the study was to determine the structure of endophytic bacteria inhabiting different parts (endosperm, germ, roots, coleoptiles, and leaves) of two wheat species, Triticum aestivum L. (cv. 'Hondia') and Triticum spelta L. (cv. 'Rokosz'), in order to provide new knowledge about the stability and/or changeability of the core microbiome in different plant organs. The endophytic core microbiome is associated with plants throughout their whole life cycle; however, plant organs can determine the actual endophytic community. Therefore, next generation sequencing with MiSeq Illumina technology was applied to identify the endophytic microbiome of T. aestivum and T. spelta. Bioinformatic analyses were performed with the use of the DADA2(1.8) package and R software (3.5.1). It was demonstrated that wheat, which is an important crop plant, was associated with beneficial endophytic bacteria inside the endosperms, germs, roots, leaves, and coleoptiles. Importantly, for the first time, biodiversity was recognized in the coleoptiles of the investigated wheat species. Flavobacterium, Pseudomonas and Janthinobacterium were shown to be common genera for both tested wheat cultivars. Among them, Pseudomonas was found to be the only endophytic genus accompanying both wheat species from the endosperm stage to the development of the leaf. Paenibacillus was recognized as a core genus for the 'Hondia' cv., whereas Pedobacter and Duganella constituted the core microbiome in the 'Rokosz' cv. In addition, the first insight into the unique and yet unrecognized endophytic microbiome of T. spelta is presented.


Assuntos
Microbiota , Triticum/microbiologia , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Biodiversidade , Endófitos/classificação , Endófitos/genética , Endófitos/isolamento & purificação , Microbiota/genética , Especificidade de Órgãos , Estruturas Vegetais/microbiologia , Especificidade da Espécie , Triticum/genética
7.
J Photochem Photobiol B ; 202: 111721, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31790881

RESUMO

The present study clearly demonstrated the significant antifungal activity of chlorophyllin-chitosan complex (Chl-CHS) after activation with visible light. This phenomenon afterwards was successfully applied for better microbial control of highly popular food- germinated wheat sprouts. Obtained results indicated that photoactivated Chl-CHS complex (0.001% Chl-0.1% CHS and 0.005% Chl-0.5% CHS, 405 nm, 76 J/cm2) considerably inhibited (83%) the growth of dominating sprout pathogenic microfungus Fusarium graminearum in vitro. Moreover, obvious delay of fungus growth by 4 days after treatment was observed. The efficiency of antifungal treatment strongly depended on used Chl-CHS complex concentration. The coating of wheat grains with Chl-CHS (0.005% Chl-0.5% CHS) and illumination with visible light (405 nm; 76 J/cm2) inactivated the molds on the surface of grains by 79%. It is important to note, that no grain surface microstructure damage observed by SEM imaging have been found. No inhibiting effects on seed germination process, viability, average weight of grains, length of seedlings and content of chlorophyll a and chlorophyll b in the seedlings or eventually visual quality after Chl-CHS coating of grains and illumination with visible light have been observed. In conclusion, chlorophyllin-chitosan coating in the concert with visible light has great potential as cost-effective, environmentally friendly and sustainable strategy for better microbial control of highly contaminated sprouts.


Assuntos
Antifúngicos/química , Quitosana/química , Clorofilídios/química , Fusarium/efeitos dos fármacos , Luz , Triticum/microbiologia , Antifúngicos/farmacologia , Fusarium/efeitos da radiação , Germinação/efeitos dos fármacos , Germinação/efeitos da radiação , Sementes/crescimento & desenvolvimento , Sementes/microbiologia , Triticum/crescimento & desenvolvimento
8.
Phytopathology ; 110(2): 370-378, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31713459

RESUMO

Fusarium head blight (FHB) and wheat yield data were gathered from fungicide trials to explore their relationship. Thirty-seven studies over 9 years and 11 locations met the criteria for inclusion in the analysis: FHB index in the untreated check ≥ 5% and the range of index in a trial ≥ 4 percentage points. These studies were grouped into two baseline yields, low (Yl ≤ 3,631 kg ha-1) or high (Yh > 3,631 kg ha-1), defined based on the median of maximum yields across trials. Attainable (disease-free) yields and FHB index were predicted using a wheat crop and a disease model, respectively, in 280 simulated trials (10 planting dates in a 28-year period, 1980 to 2007) for the Passo Fundo location. The damage coefficient was then used to calculate FHB-induced yield loss (penalizing attainable yield) for each experiment. Losses were compared between periods defined as before and after FHB resurge during the early 1990s. Disease reduction from the use of one or two sprays of a triazole fungicide (tebuconazole) was also simulated, based on previous meta-analytic estimates, and the response in yield was used in a profitability analysis. Population-average intercepts but not the slopes differed significantly between Yl (2,883.6 kg ha-1) and Yh (4,419.5 kg ha-1) baseline yields and the damage coefficients were 1.60%-1 and 1.05%-1, respectively. The magnitudes and trends of simulated yield losses were in general agreement with literature reports. The risk of not offsetting the costs of one or two fungicide sprays was generally higher (>0.75) prior to FHB resurgence but fungicide profitability tended to increase in recent years, depending on the year. Our simulations allowed us to reproduce trends in historical losses, and may be further adjusted to test the effect and profitability of different control measures (host resistance, other fungicides, etc.) on quality parameters such as test weight and mycotoxin contamination, should the information become available.


Assuntos
Agricultura , Fungicidas Industriais , Fusarium , Modelos Teóricos , Doenças das Plantas , Triticum , Agricultura/economia , Agricultura/métodos , Brasil , Simulação por Computador , Análise Custo-Benefício , Fungicidas Industriais/economia , Fungicidas Industriais/normas , Fusarium/fisiologia , Doenças das Plantas/economia , Doenças das Plantas/prevenção & controle , Triticum/microbiologia
9.
Phytopathology ; 110(2): 393-405, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31532351

RESUMO

Wheat blast is a devastating disease caused by the Triticum pathotype of Magnaporthe oryzae. M. oryzae Triticum is capable of infecting leaves and spikes of wheat. Although symptoms of wheat spike blast (WSB) are quite distinct in the field, symptoms on leaves (WLB) are rarely reported because they are usually inconspicuos. Two field experiments were conducted in Bolivia to characterize the change in WLB and WSB intensity over time and determine whether multispectral imagery can be used to accurately assess WSB. Disease progress curves (DPCs) were plotted from WLB and WSB data, and regression models were fitted to describe the nature of WSB epidemics. WLB incidence and severity changed over time; however, the mean WLB severity was inconspicuous before wheat began spike emergence. Overall, both Gompertz and logistic models helped to describe WSB intensity DPCs fitting classic sigmoidal shape curves. Lin's concordance correlation coefficients were estimated to measure agreement between visual estimates and digital measurements of WSB intensity and to estimate accuracy and precision. Our findings suggest that the change of wheat blast intensity in a susceptible host population over time does not follow a pattern of a monocyclic epidemic. We have also demonstrated that WSB severity can be quantified using a digital approach based on nongreen pixels. Quantification was precise (0.96 < r> 0.83) and accurate (0.92 < ρ > 0.69) at moderately low to high visual WSB severity levels. Additional sensor-based methods must be explored to determine their potential for detection of WLB and WSB at earlier stages.


Assuntos
Magnaporthe , Modelos Estatísticos , Imagem Óptica , Triticum , Bolívia , Magnaporthe/fisiologia , Doenças das Plantas/microbiologia , Fatores de Tempo , Triticum/microbiologia
10.
Plant Dis ; 104(1): 60-70, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31647693

RESUMO

Rapid detection is key to managing emerging diseases because it allows their spread around the world to be monitored and limited. The first major wheat blast epidemics were reported in 1985 in the Brazilian state of Paraná. Following this outbreak, the disease quickly spread to neighboring regions and countries and, in 2016, the first report of wheat blast disease outside South America was released. This Asian outbreak was due to the trade of infected South American seed, demonstrating the importance of detection tests in order to avoid importing contaminated biological material into regions free from the pathogen. Genomic analysis has revealed that one particular lineage within the fungal species Pyricularia oryzae is associated with this disease: the Triticum lineage. A comparison of 81 Pyricularia genomes highlighted polymorphisms specific to the Triticum lineage, and this study developed a real-time PCR test targeting one of these polymorphisms. The test's performance was then evaluated in order to measure its analytical specificity, analytical sensitivity, and robustness. The C17 quantitative PCR test detected isolates belonging to the Triticum lineage with high sensitivity, down to 13 plasmid copies or 1 pg of genomic DNA per reaction tube. The blast-based approach developed here to study P. oryzae can be transposed to other emerging diseases.


Assuntos
Agricultura , Genoma Fúngico , Magnaporthe , Reação em Cadeia da Polimerase em Tempo Real , Triticum , Agricultura/métodos , Genes Fúngicos/genética , Genômica , Magnaporthe/genética , Doenças das Plantas/microbiologia , América do Sul , Triticum/microbiologia
11.
Plant Dis ; 104(1): 260-268, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31644391

RESUMO

Rye (Secale cereale L.) is an important gene donor for wheat improvement because of its many valuable traits, especially disease resistance. Development of novel wheat-rye translocations with disease resistance can contribute to transferring resistance into common wheat. In a previous study, a wheat-rye T4BL·4RL and T7AS·4RS translocation line (WR41-1) was developed by distant hybridization, and it was speculated that its resistance to powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), was derived from rye based on pedigree analysis. To make accurate use of chromosome 4R in wheat improvement, a set of new 4R translocations involving different arm translocations (e.g., 4RS monosomic, 4RL monosomic, 4RL disomic, 4RS monosomic plus 4RL monosomic, 4RS monosomic plus 4RL disomic, and 4RS disomic plus 4RL disomic translocations) was developed from crosses with common wheat. Those translocations were characterized by genomic in situ hybridization and expressed sequence tag simple sequence repeat marker analysis. To confirm the source of powdery mildew resistance, the translocation plants were tested against Bgt isolate E09. The results indicated that all translocations with 4RL were resistant at all tested growth stages, whereas those with only 4RS translocation or no alien translocation were susceptible. This further indicated that the powdery mildew resistance of WR41-1 was derived from the alien chromosome arm 4RL. To effectively use 4RL resistance in wheat improvement, two competitive allele-specific PCR markers specific for chromosome arm 4RL were developed to detect the alien chromosome in the wheat genome. These new translocation lines with diagnostic markers can efficiently serve as important bridges for wheat improvement.


Assuntos
Ascomicetos , Resistência à Doença , Secale , Triticum , Cromossomos de Plantas/genética , Resistência à Doença/genética , Secale/genética , Secale/microbiologia , Translocação Genética , Triticum/genética , Triticum/microbiologia
12.
Int J Syst Evol Microbiol ; 70(1): 126-138, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31613740

RESUMO

Two novel Actinobacteria, designated strains NEAU-YY421T and NEAU-YY642T, were isolated from the rhizosphere soil of wheat (Triticum aestivum L.) collected from Zhumadian, Henan Province, PR China and characterized using a polyphasic approach. Phylogenetic analyses based on 16S rRNA gene sequences showed that strains NEAU-YY421T and NEAU-YY642T belonged to the genus Streptomyces and strain NEAU-YY421T was most closely related to Streptomyces fumanus CGMCC 4.1732T (97.9 % sequence similarity) and Streptomyces naganishii DSM 40282T (97.8 %), and that of strain NEAU-YY642T to Streptomyces zhaozhouensis LZS-5T (98.0 %) and Streptomyces sedi YIM 65188T (97.5 %). The cell walls of the two strains contained ll-diaminopimelic acid as the diagnostic diamino acid and the whole-cell hydrolysates were glucose and ribose. Multilocus sequence analysis using the concatenated sequences of the atp D, gyr B, rec A, rpo B and trp B genes showed that the two strains formed separate branches in the genus Streptomyces. Moreover, a combination of DNA-DNA hybridization results and cultural and physiological properties indicated that the two strains can be distinguished from their closest phylogenetic relatives. Therefore, strains NEAU-YY421T and NEAU-YY642T belong to two novel species in the genus Streptomyces, for which the names Streptomyces triticagri sp. nov. (NEAU-YY421T=CGMCC 4.7476T=DSM 106775T) and Streptomyces triticirhizae sp. nov. (NEAU-YY642T=CCTCC AA 2018092T=DSM 107172T) are proposed, respectively.


Assuntos
Filogenia , Rizosfera , Microbiologia do Solo , Streptomyces/classificação , Triticum/microbiologia , Técnicas de Tipagem Bacteriana , Composição de Bases , Parede Celular/química , China , DNA Bacteriano/genética , Ácido Diaminopimélico/química , Ácidos Graxos/química , Genes Bacterianos , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Streptomyces/isolamento & purificação
13.
Int J Syst Evol Microbiol ; 70(1): 139-145, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31622227

RESUMO

A novel actinomycete, designated strain NEAU-HEGS1-5T, was isolated from the ear of wheat (Triticum aestivum L.) and characterized using a polyphasic approach. The morphological and chemotaxonomic characteristics of the strain coincided with those of members of the genus Microbispora. The results of 16S rRNA gene sequence analysis showed that the isolate was most closely related to Microbispora bryophytorum NEAU-TX2-2T (99.3 %), Microbispora camponoti 2C-HV3T (99.2 %), Microbispora amethystogenes JCM 3021T (99.1 %) and Microbispora rosea subsp. rosea JCM 3006T (98.5 %). However, two tree-making algorithms supported the position that strain NEAU-HEGS1-5T formed a distinct clade with M. bryophytorum NEAU-TX2-2T, M. camponoti 2C-HV3T and M. rosea subsp. rosea JCM 3006T. Furthermore, multilocus sequence analysis based on the 16S-gyr B-rpo B genes and a combination of DNA-DNA hybridization results and some physiological and biochemical properties demonstrated that the strain could be distinguished from its closest relatives. Therefore, it is proposed that strain NEAU-HEGS1-5T should be classified as representative of a novel species of the genus Microbispora, for which the name Microbispora fusca sp. nov. is proposed. The type strain is NEAU-HEGS1-5T (=CCTCC AA 2019030T=DSM 104648T).


Assuntos
Actinomycetales/classificação , Filogenia , Triticum/microbiologia , Actinomycetales/isolamento & purificação , Técnicas de Tipagem Bacteriana , Composição de Bases , China , DNA Bacteriano/genética , Ácidos Graxos/química , Genes Bacterianos , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , Análise de Sequência de DNA
14.
Mol Biol Evol ; 37(1): 221-239, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31553475

RESUMO

Transposable elements (TEs) are drivers of genome evolution and affect the expression landscape of the host genome. Stress is a major factor inducing TE activity; however, the regulatory mechanisms underlying de-repression are poorly understood. Plant pathogens are excellent models to dissect the impact of stress on TEs. The process of plant infection induces stress for the pathogen, and virulence factors (i.e., effectors) located in TE-rich regions become expressed. To dissect TE de-repression dynamics and contributions to virulence, we analyzed the TE expression landscape of four strains of the major wheat pathogen Zymoseptoria tritici. We experimentally exposed strains to nutrient starvation and host infection stress. Contrary to expectations, we show that the two distinct conditions induce the expression of different sets of TEs. In particular, the most highly expressed TEs, including miniature inverted-repeat transposable element and long terminal repeat-Gypsy element, show highly distinct de-repression across stress conditions. Both the genomic context of TEs and the genetic background stress (i.e., different strains harboring the same TEs) were major predictors of de-repression under stress. Gene expression profiles under stress varied significantly depending on the proximity to the closest TEs and genomic defenses against TEs were largely ineffective to prevent de-repression. Next, we analyzed the locus encoding the Avr3D1 effector. We show that the insertion and subsequent silencing of TEs in close proximity likely contributed to reduced expression and virulence on a specific wheat cultivar. The complexity of TE responsiveness to stress across genetic backgrounds and genomic locations demonstrates substantial intraspecific genetic variation to control TEs with consequences for virulence.


Assuntos
Ascomicetos/genética , Ascomicetos/patogenicidade , Evolução Biológica , Elementos de DNA Transponíveis , Estresse Fisiológico , Perfilação da Expressão Gênica , Redes Reguladoras de Genes , Genoma Fúngico , Triticum/microbiologia , Virulência/genética
15.
Phytopathology ; 110(2): 257-266, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31448998

RESUMO

Bacterial leaf streak (BLS) of wheat and barley has been a disease of increasing concern in the Upper Midwest over the past decade. In this study, intra- and interfield genetic and pathogenic diversity of bacteria causing BLS in Minnesota was evaluated. In 2015, 89 strains were isolated from 100 leaf samples collected from two wheat and two barley fields naturally infected with BLS. Virulence assays and multilocus sequence alignments of four housekeeping genes supported pathovar identifications. All wheat strains were pathogenic on wheat and barley and belonged to the same lineage as the Xanthomonas translucens pv. undulosa-type strain. All barley strains were pathogenic on barley but not on wheat. Three lineages of barley strains were detected. The frequency and number of sequence types of each pathovar varied within and between fields. A significant population variance was detected between populations of X. translucens pv. undulosa collected from different wheat fields. Population stratification of X. translucens pv. translucens was not detected. Significant differences in virulence were detected among three dominant sequence types of X. translucens pv. undulosa but not those of X. translucens pv. translucens. Field trials with wheat and barley plants inoculated with strains of known sequence type and virulence did not detect significant race structures within either pathovar. Knowledge of virulence, sequence types, and population structures of X. translucens on wheat and barley can support studies on plant-bacterial interactions and breeding for BLS disease resistance.


Assuntos
Variação Genética , Hordeum , Doenças das Plantas , Triticum , Xanthomonas , Hordeum/microbiologia , Especificidade de Hospedeiro , Minnesota , Doenças das Plantas/microbiologia , Triticum/microbiologia , Xanthomonas/classificação , Xanthomonas/genética , Xanthomonas/patogenicidade
16.
Plant Dis ; 104(1): 44-51, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31730412

RESUMO

Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici Erikss. (Pst), is an important disease of wheat. In China, Pst management has focused on the Gansu region where the pathogen can complete its annual cycle, including oversummering and overwintering. From this region, Pst inoculum is dispersed to the southern Yangtze River region in the late autumn/early winter and then to the main wheat production regions in the following spring. We used historical weather data (1995 to 2016) and field stripe rust assessment data (8 years) in the spring to evaluate the performance of a published model for predicting the potential of Pst overwintering in the Gansu region. Both predicted and observed values of rust overwintering in the Gansu region varied greatly between years and between sites within a single year, indicating the value of predicting rust overwintering for disease management. The model predictions fitted with observed values satisfactorily. All high incidences of rust in the spring were observed in the fields of the monitoring sites where the high potential of overwintering was predicted. Conversely, the predicted rust overwintering potential was also close to zero in the fields where rust was not observed in the spring. There were many false-positive predictions, which may be attributable to the absence of rust in autumn seedlings. This model can be used to target rust management in the spring and its effectiveness will be further improved if autumn rust assessment can be carried out.


Assuntos
Basidiomycota , Modelos Biológicos , Estações do Ano , Triticum , Basidiomycota/fisiologia , China , Doenças das Plantas/microbiologia , Triticum/microbiologia
17.
Lett Appl Microbiol ; 70(1): 48-54, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31642537

RESUMO

This study aims to describe the native microbiota of fermented spelt, taking into consideration both lactic acid bacteria (LAB) and yeasts, for which little data are available. Five samples of commercial spelt flour were subjected to spontaneous fermentation to obtain a type I sourdough. A total of 186 LAB and 174 yeast isolates were selected at different refreshment steps and subjected to further analyses. Within LAB, coccal isolates constituted 78·5% of the total LAB, with the dominance of Pediococcus pentosaceus. Although documented before as a component, this is the first report of a spelt sourdough fermentation dominated by this homofermentative LAB, characterized by a high acidification rate, ability to utilize a wide range of carbon sources and to grow in high osmolarity conditions. Yeast communities resulted in four dominant species, Saccharomyces cerevisiae, Wickerhamomyces anomalus, Pichia fermentans and Clavispora lusitaniae. This study highlights for the first time the biodiversity and dynamics of yeast communities involved in sourdough fermentation of spelt. Compared to commercial baker's yeast, autochthonous W. anomalus, P. fermentans and S. cerevisiae isolates show a good performance, and their use could be an advantage for their acquired adaptation to the environment, providing stability to the fermentation process. SIGNIFICANCE AND IMPACT OF THE STUDY: Nowadays, there is a renewed interest in products based on spelt. This 'ancient grain' is a highly nutritional grain; however, its use is limited to bread-making processes, which are not standardized. The low baking and sensory quality of spelt can be overcome through fermentation processes. However, the autochthonous microbiota of spelt sourdough is poorly known. This study highlights the dynamics of microbial communities involved in sourdough fermentation of spelt and provides the basis for the selection of autochthonous cultures, with the aim of improving the nutritional potential of spelt and its rheology and bread-making properties.


Assuntos
Pão/microbiologia , Lactobacillales/metabolismo , Consórcios Microbianos , Triticum/microbiologia , Leveduras/metabolismo , Biodiversidade , Pão/análise , Fermentação , Farinha/microbiologia , Microbiologia de Alimentos , Lactobacillales/classificação , Lactobacillales/genética , Lactobacillales/isolamento & purificação , Triticum/metabolismo , Leveduras/classificação , Leveduras/genética , Leveduras/isolamento & purificação
18.
J Sci Food Agric ; 100(2): 803-810, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31612503

RESUMO

BACKGROUND: New evidence has shown that arbuscular mycorrhizal (AM) fungi can contribute to the aluminum (Al3+ ) tolerance of host plants growing in acidic soils with phytotoxic levels of Al3+ . The aim of this study was to investigate the role of AM fungi isolated from naturally occurring Al3+ acidic soils in conferring host tolerance to Al3+ toxicity in three wheat cultivars differing in Al3+ sensitivity. The experiment was conducted in a soilless substrate (vermiculite/perlite, 2:1 v/v) using two Al3+ -tolerant wheat genotypes and one Al3+ -sensitive wheat genotype. The wheat was colonized with a consortium of AM fungi isolated from an Andisol, with or without Al3+ at a concentration of 200 µmol L-1 . RESULTS: The response of wheat to Al3+ in the medium was dependent on both the plant genotype and AM colonization. The benefits of the AM fungi to the wheat cultivars included an increased P concentration and relatively low Al3+ accumulation in the plants. This was achieved through two mechanisms. First, the metal-chelating capacity of the AM fungi was clear in two of the cultivars ('Tukan' and 'Porfiado'), in which the enhanced extraradical mycelium development was able to retain Al3+ in the glomalin and hyphae. Second, the increased AM-induced acid phosphatase activity in the rhizosphere of the other cultivar ('Atlas 66') increased host nutrition possibly by hyphae-mediated nutrient uptake and glomalin-related soil protein. CONCLUSION: The results suggest that the role of AM fungi in cultivar-specific Al3+ detoxification can be achieved by increased extraradical mycelial filters and enhanced bioavailability of P in the host rhizosphere. © 2019 Society of Chemical Industry.


Assuntos
Alumínio/metabolismo , Micorrizas/metabolismo , Fósforo/metabolismo , Poluentes do Solo/metabolismo , Triticum/microbiologia , Alumínio/análise , Alumínio/toxicidade , Hifas/crescimento & desenvolvimento , Hifas/metabolismo , Micélio/crescimento & desenvolvimento , Micélio/metabolismo , Micorrizas/crescimento & desenvolvimento , Fósforo/análise , Poluentes do Solo/análise , Poluentes do Solo/toxicidade , Triticum/crescimento & desenvolvimento , Triticum/metabolismo
19.
J Sci Food Agric ; 100(2): 863-873, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31646638

RESUMO

BACKGROUND: Wheat is the most important winter crop in the world, being affected by the presence of fungal, mainly those belonging to the Fusarium genus. Fusarium head blight (FHB) is a serious disease that causes important economic damage and quantitative/qualitative losses, with Fusarium graminearum and Fusarium poae being two of the most isolated species worldwide. The present study aimed to evaluate the interaction between F. graminearum and F. poae and the effects on disease parameters, grain quality and mycotoxin contamination on five wheat genotypes under field conditions during three growing seasons. RESULTS: Statistical differences between Fusarium treatments were found for disease parameters, grain quality and mycotoxin contamination during the 2014/2015 growing season. High values of incidence (58.00 ± 8.00%), severity (6.28 ± 1.51%) and FHB index (4.72 ± 1.35) were observed for F. graminearum + F. poae treatment. Regarding grain quality, the results showed that the degradation of different protein fractions depends on each Fusarium species: glutenins were degraded preferably by F. graminearum (-70.82%), gliadins were degraded preferably by F. poae (-29.42%), whereas both protein fractions were degraded when both Fusarium species were present (-60.91% and -16.51%, respectively). Significant differences were observed for mycotoxin contamination between genotypes, with Proteo being the most affected (DON = 12.01 ± 3.67 µg g-1 ). In addition, we report that 3-ADON predominated over 15-ADON in the three seasons evaluated. CONCLUSION: Variations in plant-pathogen interaction (Fusarium-wheat pathosystem) should be considered at least in years with favorable climatic conditions for FHB development, as a result of the potential impact of this disease on grain quality and mycotoxin contamination. © 2019 Society of Chemical Industry.


Assuntos
Fusarium/metabolismo , Micotoxinas/análise , Doenças das Plantas/microbiologia , Triticum/química , Triticum/microbiologia , Fusarium/classificação , Micotoxinas/metabolismo , Estações do Ano , Sementes/química , Sementes/microbiologia
20.
Int J Food Microbiol ; 313: 108381, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31670167

RESUMO

As a raw agricultural commodity, wheat is exposed to microbial contamination; therefore, enteric pathogens may be among its microbiota creating a food safety risk in milled products. This research evaluates (1) the effectiveness of organic acids dissolved in saline solutions to reduce the counts of pathogenic microorganisms in soft and hard wheat, and also investigates the effect of seasonal temperature on (2) survivability of pathogens in wheat kernels and on (3) pathogen inactivation during tempering with saline organic acid solutions. Wheat samples were inoculated with cocktails of either 5 serovars of Salmonella enterica, 5 E. coli O157:H7 or 6 non-O157 Shiga toxin-producing E. coli (STEC) strains to achieve a concentration of ~7 log CFU/g. Inoculated samples were allowed to stand for 7-days at temperatures (2.0, 10.8, 24.2, 32 °C) corresponding to those experienced during winter, spring/fall, and summer (average and maximum) in the main wheat growing regions in the state of Nebraska, USA. Besides water, solutions containing acid (acetic or lactic 2.5% or 5.0% v/v) and NaCl (~26% w/v) were used for tempering the wheat to 15.0% (soft) and 15.5% (hard) moisture at the different seasonal temperatures. The survival of pathogenic microorganisms throughout the resting period, and before and after tempering was analyzed by plating samples on injury-recovery media. The survival rate of pathogenic microorganisms on wheat kernels was higher at temperatures experienced during the winter (2.0 °C) and spring/fall (10.8 °C) months. Regardless of tempering temperature, the initial pathogen load was reduced significantly by all solutions when compared to the control tempered with water (P ≤ .05). The combination of lactic acid (5.0%) and NaCl was the most effective treatment against Salmonella enterica, E. coli O157:H7 and non-O157 STEC, with average reduction values of 1.8, 1.8 and 1.6 log CFU/g for soft wheat and 2.6, 2.4 and 2.4 log CFU/g for hard wheat, respectively. Implementation of organic acids and NaCl in tempering water may have the potential to reduce the risk of pathogen contamination in milled products.


Assuntos
Ácidos/farmacologia , Manipulação de Alimentos/métodos , Cloreto de Sódio/farmacologia , Triticum/microbiologia , Ácidos/química , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/crescimento & desenvolvimento , Manipulação de Alimentos/instrumentação , Microbiologia de Alimentos , Inocuidade dos Alimentos , Salmonella enterica/efeitos dos fármacos , Salmonella enterica/crescimento & desenvolvimento , Estações do Ano , Temperatura Ambiente
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