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1.
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2.
Fusarium head blight is one of the most serious cereal diseases of the world. Epidemics of Fusarium head blight can lead to a decline in grain quality and yield. In addition, grains often become contaminated with mycotoxins, which are harmful to humans and animals. In a field survey of winter wheat in Switzerland, Fusarium graminearum proved to be the most prevalent species responsible for head blight and deoxynivalenol the most common mycotoxin. To elucidate and quantify single or combined effects of cropping factors on F. graminearum infestation and to reduce the risk of mycotoxin contamination of wheat under conservation tillage, we developed the decision support system FusaProg. Our model takes into account the effects of cropping factors, previous crops, soil and straw management, as well as the F. graminearum susceptibility of the planted variety. These factors are used as driving variables and are combined with the prevailing weather conditions and growth stage in order to predict the deoxynivalenol content of a specific wheat plot before harvest. To use FusaProg as a threshold‐based tool to control F. graminearum with optimized timing of fungicide applications, forecasts of deoxynivalenol contents are conducted during the flowering period. FusaProg is an Internet‐based decision support system which not only provides information about the local and regional F. graminearum infection risks; it also forecasts plot‐specific deoxynivalenol contamination of winter wheat. In 2006, the system was evaluated by Swiss cantonal plant protection officers, and in 2007, the system will be made available to Swiss wheat producers.  相似文献   

3.
The fungal pathogen Fusarium graminearum is the causal agent of fusarium head blight in wheat and other small grain cereals. This fungus is known to produce high amounts of cell wall‐degrading enzymes during infection of wheat spikes. In addition, wheat tissue is particularly rich in xylan, which can be hydrolysed by fungal xylanases. In order to establish the role of F. graminearum xylanase activity in pathogenicity, targeted gene disruption of the F. graminearum xyr1 gene, encoding the major regulator of xylanase gene expression, was performed. When grown on xylan as carbon source, the xylanase activity of the Δxyr1 mutant was dramatically reduced and fungal growth was significantly reduced compared to the wildtype fungus. When grown on carboxymethylcellulose, the cellulolytic activity of the mutant was also reduced and the mutant did not grow on wheat cell walls. The disruption of the xyr1 gene greatly reduced the expression of xylanase‐encoding genes both in vitro and during wheat spike infection, thus confirming the involvement of F. graminearum Xyr1 in the regulation of genes controlling xylan degradation. However, despite the deep impact caused by xyr1 gene disruption on the expression of xylanase genes and on total xylanase activity, the virulence of the Δxyr1 mutant appeared unaffected on Triticum aestivum and T. durum spikes and on soybean seedlings. In conclusion, although a possible role for residual xylanase activity in the virulence of F. graminearum cannot be conclusively excluded, the results question the importance of xylanase activity during the infection process.  相似文献   

4.
Fusarium Head Blight is a major disease of wheat and an important contributor to the reduced cultivation of wheat in South Africa, where the crop often is grown under irrigation. We collected Fusarium isolates from 860 Fusarium Head Blight-infected wheat heads in seven irrigated wheat-growing areas of South Africa. Six Fusarium species, i.e., F. chlamydosporum, F. crookwellense, F. culmorum, F. equiseti, F. graminearum and F. semitectum were recovered, three of which, i.e., F. chlamydosporum, F. equiseti and F. semitectum, were not previously associated with Fusarium Head Blight in South Africa. Fusarium graminearum occurred at high frequencies at all seven locations. Based on polymerase chain reaction (PCR) assays of diagnostic sequences, more isolates were predicted to produce deoxynivalenol than nivalenol. Fusarium graminearum (sensu lato) appears to be the primary causal agent of Fusarium Head Blight in irrigated wheat in South Africa, which may not be the case for wheat cultivated under rain-fed conditions. Rotations of irrigated wheat with other graminaceous crops and maize could increase fungal inoculum and disease pressure. The establishment of Fusarium Head Blight in the irrigated wheat region of the country means that resistant lines and alternative agronomic practices are needed to limit disease severity, yield losses and mycotoxin contamination.  相似文献   

5.
为明确植物病原真菌禾谷镰刀菌Fusarium graminearum全生活史的转录组特征和基因表达模式,采用生物信息学技术对其生活史不同阶段15个时期或组织的链特异性RNA-seq数据进行分析。结果表明,共有8 106个基因在所有时期均有表达,为禾谷镰刀菌生活史核心基因,占总基因数的47.2%;有性生殖和侵染过程中表达的基因数相对较多,其中有性生殖后期表达的基因数最多,达15 221个;无性产孢和侵染小麦穗过程中基因表达水平整体较高,而分生孢子中基因表达水平最低。在燕麦培养基上禾谷镰刀菌气生菌丝的基因表达模式与侵染过程中的基因表达模式较为相似,而与营养生长菌丝的基因表达模式差异较大。该菌次生代谢物合成特征酶基因和分泌蛋白基因的表达模式均分成3类,即分别在侵染、营养生长和有性生殖过程上调表达,暗示其在生活史不同阶段的特异性功能。  相似文献   

6.
山东省小麦赤霉病菌种群组成及其致病力分化   总被引：2，自引：2，他引：0  
由禾谷镰孢菌群Fusarium graminearum clade引起的赤霉病是小麦的重要病害。为明确山东省小麦赤霉病菌的种群组成及其致病力,于2011年和2012年从山东省15地市分离了95株小麦赤霉病菌,在形态和分子生物学鉴定种的基础上,采用鉴定B型毒素化学型的特异性引物进行毒素化学型分析。在95个菌株中,93株分离物为禾谷镰孢菌F.graminearum,2株为燕麦镰孢菌F.avenaceum。94株分离物为脱氧雪腐镰孢菌烯醇(deoxynivalenol,DON)化学型,1株为雪腐镰孢菌烯醇(nivalenol,NIV)化学型。在94株DON毒素化学型菌株中,90株为15-乙酰脱氧雪腐镰孢菌烯醇(15-acetyldeoxynivalenol,15-AcDON)化学型,4株为3-乙酰脱氧雪腐镰孢菌烯醇(3-acetyldeoxynivalenol,3-AcDON)化学型。在小麦扬花期,采用单花滴注接种法对29个菌株进行了致病力测定,供试菌株的致病力分化明显。表明在山东省冬小麦产区,产15-AcDON毒素的F.gra-minearum是小麦赤霉病菌的优势种群。  相似文献   

7.
Fusarium pseudograminearum, F. culmorum and F. graminearum are the most important fusarium crown rot (FCR) causal agents. They have the common ability to biosynthesize deoxynivalenol (DON). To elucidate the behaviour of each of the three species, a comparative study was carried out to investigate symptom progression, fungal systemic growth and translocation of DON following stem base inoculation of soft wheat. FCR symptoms were mainly localized in the inoculated area, which extended up to the second node for all inoculated species. Only the most aggressive strains caused symptoms up to the third node. Real‐time quantitative PCR showed that fungal colonization reached the third node for all the tested species, but a low percentage of plants showed colonization above the third node following inoculation with the most aggressive strains. Fungal growth was detected in symptomless tissues but none of the three species was able to colonize as far as the head tissues. However, even if the pathogens were not detected in the heads, DON was detected in head tissues of the plants inoculated with the most aggressive strains. These results demonstrate that F. pseudograminearum, F. culmorum and F. graminearum, under the same experimental conditions, follow a similar pattern of symptom progression, fungal colonization and DON translocation after stem base infection. Differences in the extent of symptoms, fungal colonization and mycotoxin distribution were mainly attributable to strain aggressiveness. These findings provide comparative information on the events following infection of the stem base of wheat by three of the most important FCR casual agents.  相似文献   

8.
Fungal species comprising the Fusarium graminearum species complex (FGSC) may cause disease in maize and wheat. Host preference within the FGSC has been suggested, in particular F. boothii towards maize ears. Therefore, the disease development and mycotoxin production of five FGSC species in maize and wheat grain was determined. Eighteen isolates representing F. acaciae-mearnsii, F. boothii, F. cortaderiae, F. graminearum and F. meridionale were used. Each isolate was inoculated on maize ears and wheat heads to determine host preferences. Disease severity and disease incidence was measured for maize and wheat, respectively. Fungal colonisation and mycotoxins, deoxynivalenol (DON), nivalenol and zearalenone, was also quantified. Isolates differed significantly (P < 0.05) in their ability to produce symptoms on maize ears, however, no significant differences between FGSC species were determined. Similarly, significant differences (P < 0.05) between isolates but not between FGSC species in disease incidence on wheat were determined. The isolates also differed significantly (P < 0.05) in their ability to colonise maize and wheat grain. No significant differences in fungal colonisation, among the five FGSC species, were determined in field grown maize. However, under greenhouse conditions, F. boothii was the most successful coloniser of maize grain (P < 0.05). In wheat, F. graminearum colonised the grain more successfully and produced significantly more (P < 0.05) DON than the other species. Fusarium boothii isolates were the best colonisers and mycotoxin producers in maize, and F. graminearum isolates in wheat. The selective advantage of F. boothii to cause disease on maize was supported in this study.  相似文献   

9.
Fusarium head blight (FHB) is one of the most important fungal diseases affecting wheat worldwide and it is caused mainly by species within the Fusarium graminearum species complex (FGSC). This study evaluated the presence of FGSC in durum wheat from the main growing area in Argentina and analyzed the trichothecene genotype and chemotype of the strains isolated. Also, the genetic variability of the strains was assayed using ISSR markers. Molecular analysis revealed that among the strains isolated and identified morphologically as F. graminearum, there were 14 strains identified as F. cerealis. Also, it revealed that durum wheat grains were mostly contaminated by F. graminearum, being this the only species reported so far, within the FGSC, affecting durum wheat in Argentina. Analysis of molecular variance (AMOVA) indicated a high genetic variability within rather than between F. graminearum populations. All F. graminearum strains presented 15ADON genotype and were able to produce DON while all F. cerealis strains presented the NIV genotype and most of them were able to produce this toxin. The finding of F. cerealis in durum wheat grains indicates the need for investigating if this fungus is the responsible for the NIV contamination found in wheat in Argentina.  相似文献   

10.
Fusarium graminearum causes fusarium head blight (FHB) of wheat and gibberella ear rot (GER) of corn in Canada and also contaminates grains with trichothecene mycotoxins. Very little is known about trichothecene diversity and population structure of the fungus from corn in Ontario, central Canada. Trichothecene genotypes of F. graminearum isolated from corn (n = 452) and wheat (n = 110) from 2010 to 2012 were identified. All the isolates were deoxynivalenol (DON) type. About 96% of corn isolates and 98% of wheat isolates were 15‐acetyl deoxynivalenol (15ADON) type. The fungal population structures from corn (n = 313) and wheat (n = 73) were compared using 10 variable number tandem repeat (VNTR) markers. The fungal populations and subpopulations categorized based on host, cultivar groups, years and geography showed high gene (H = 0.818–0.928) and genotypic (GD = 0.999–1.00) diversity. Gene flow was also high between corn and wheat population pairs (Nm = 8.212), and subpopulation pairs within corn (Nm = 7.13–23.614) or wheat (Nm = 19.483) populations. Phylogenetic analysis revealed that isolates from both hosts were F. graminearum clade 7. These findings provide baseline data on 3‐acetyl deoxynivalenol (3ADON) and 15ADON profiles of F. graminearum isolates from corn in Canada and are useful in evaluating mycotoxin contamination risks in corn and wheat grains. Understanding the fungal genetic structure will assist evaluation and development of resistant cultivars/germplasm for FHB on wheat and GER on corn.  相似文献   

11.
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12.
The presence of Fusarium spp. causing Fusarium head blight (FHB) of wheat was studied in Flanders (Belgium) in 2007 and 2008. Symptoms, deoxynivalenol content (DON), Fusarium spp. and trichothecene chemotypes were determined at seven locations on different commercial wheat varieties. Overall, significant differences in disease pressure between locations and varieties were observed within 1 year. In addition, we were able to detect consistent and significant resistance differences among the common varieties both under high disease pressure (2007) and low disease pressure (2008). The accumulation of DON was not related to the presence of F. graminearum but showed a clear correlation with rainfall during and after the period of anthesis. During the two-year survey, characterisation of 756 Fusarium samples by species-specific PCR designated F. poae and F. graminearum as the predominant species in Flanders. Furthermore, most of the ears were colonised by multiple FHB pathogens in 2007 whereas the Fusarium population was less complex in 2008. Log-linear analysis of these multiple (two- and three-way) species interactions revealed a clear correlation between F. poae and several pathogens of the FHB disease complex. Finally, chemotype analysis showed that F. culmorum and F. graminearum were respectively of the NIV chemotype and DON chemotype. 3-ADON and 15-ADON chemotypes occurred in more or less equal amounts within the F. graminearum population both in 2007 and 2008. The congruence of these results with observations throughout Europe are discussed.  相似文献   

13.
Two Fusarium graminearum strains were cultured in glucose yeast extract peptone broth or minimal medium broth to measure the production of mycelial biomass, pH, mycotoxins, and aurofusarin pigment, when limited to single carbon sources (at 1%), including xylan, cellulose, starch, or glucose. A random complete block design with factorial arrangement and analysis of variance at a significance level of 0.01 were employed to test for treatment differences. Overall, the F. graminearum strains produced significantly more biomass, deoxynivalenol, and aurofusarin with xylan than with cellulose. No significant differences were found in terms of 15–acetyldeoxynivalenol production from the four carbon sources. The presence of significant interactions between the strains, carbon sources, and media led to the following specific differences. In yeast extract peptone broth, R-9828 strain yielded significantly more deoxynivalenol production with xylan than cellulose and R-9832 produced significantly more mycelium (biomass) with xylan than cellulose. R-9828 strain yielded significantly more deoxynivalenol production than the R-9832 strain. Also in yeast extract peptone broth, cellulose led to significantly higher pH values than other carbons, which might be due to the limited ability of the Fusarium strains to utilize cellulose as an energy source. Aurofusarin was the only expressed analyte to show a significant difference in minimal medium broth, and R-9832 produced significantly more aurofusarin with xylan than with cellulose in the broth. These results suggest that xylan may induce Fusarium growth and deoxynivalenol production to assist the infection process and may support the theory that F. graminearum invades through xylan in the cell walls of cereals.  相似文献   

14.
Foot rot and crown rot are fungal diseases of wheat caused by a complex of Fusarium species. They have a huge economic impact mainly due to yield reduction. A survey was conducted to identify four Fusarium species, occurring on wheat stem bases, using species-specific PCR assays in samples collected during spring of 2012. The dominant species was F. graminearum, which was identified in above 64 % of samples. F. culmorum was detected in 15.71 %, F. poae in 15.71 % and F. sporotrichioides in 5.71 % wheat fields. Most of the wheat fields in the eastern Poland were infected with at least one or two of Fusarium species, while in central Poland no Fusarium species were identified in most of the fields. The presence of F. graminearum tends to favor the presence of F. culmorum and this effect was visible also for F. poae and F. sporotrichioides. The frequency of F. graminearum and F. culmorum detections were highest where wheat crops were preceded by maize and in the samples from late sown fields. The opposite observation was made for F. poae and F. sporotrichioides, where the number of detections of these species was higher in samples from early sown fields. The number of detected Fusarium species was significantly lower in samples collected from fields protected with autumn herbicide in comparison to unprotected fields. The rate of autumn N fertilization did not affect the number of Fusarium detections.  相似文献   

15.
Fusarium graminearum is an important pathogen causing Fusarium head blight (FHB) on wheat and barley and Fusarium ear rot (FER) on maize, and harvested grains often are contaminated with trichothecenes such as deoxynivalenol (DON) and nivalenol (NIV) that are a major health and food safety concern due to their toxicity to humans and farm animals. In this study, species identity and trichothecene toxin potential of 294 members of the Fusarium graminearum species complex (FGSC) collected from wheat, barley and maize in France in 2011 was determined using a microsphere-based multilocus genotyping assay. F. graminearum was predominant on all three hosts, but three isolates of F. cortaderiae and two isolates representing F. graminearum × F. boothii hybrids were also identified from maize. The 15-ADON trichothecene chemotype predominated on all three hosts, representing 94.7 %, 87.8 % and 85.4 % of the strains on barley (N?=?19), wheat (N?=?90), and maize (N?=?185), respectively. However, the NIV chemotype was found in 12.2 % of the wheat isolates and in 14.6 % of the maize isolates. Only a single FGSC isolate from this study, originating from barley, was found to have the 3-ADON chemotype. Regional differences could be observed in the distribution of the 15-ADON and NIV chemotypes, with the NIV producing-isolates being present at higher frequency (21.2 %) in the South of France compared to the rest of the country (4.4 %). Such information is critical because of the increased concern associated with NIV contamination of cereals. In addition, these results are needed to develop management strategies for FHB and FER in France and to improve understanding of the distribution and significance of FGSC diversity in Europe and worldwide.  相似文献   

16.
Fusarium head blight (FHB) of wheat and other small-grain cereals is a disease complex caused by several fungal species. To monitor and quantify the major species in the FHB complex during the growing season, real-time PCR was developed. TaqMan primers and probes were designed that showed high specificity for Fusarium avenaceum, F. culmorum, F. graminearum, F. poae and Microdochium nivale var. majus. Inclusion of an internal PCR control and serial dilutions of pure genomic DNAs allowed accurate determination of the concentration of fungal DNA for each of these species in leaves, ears as well as harvested grains of winter wheat. The DNA concentration of F. graminearum in grain samples correlated (r 2= 0.7917) with the incidence of this species on the grain as determined by isolation from individual kernels. Application of the TaqMan technology to field samples collected in 40 wheat crops in the Netherlands during the growing season of 2001 revealed that M. nivale var. majus predominated on leaves early in the season (GS 45-65). Ears and harvested grains from the same fields, however, showed F. graminearum as the major species. In 2002, grain samples from 40 Dutch fields showed a much wider range of species, whereas in ears from 29 wheat crops in France, F. graminearum was the predominant species. The concentration of DON correlated equally well with the incidence of the DON-producing species F. culmorum and F. graminearum in the grain samples (r 2= 0.8232) as well as with total DNA of both these species (r 2= 0.8259). The Fusarium TaqMan technology is an important tool to quantify and monitor the dynamics of individual species of the complex causing FHB in cereals during the growing season. This versatile tool has been applied in a comparison of different genotypes, but can also be applied to other disease management systems, e.g. fungicide treatments.  相似文献   

17.
Fusarium head blight in wheat spikes is associated with production of mycotoxins by the fungi. Although flowering is recognized as the most favourable host stage for infection, a better understanding of infection timing on disease development and toxin accumulation is needed. This study monitored the development of eight characterized isolates of F. graminearum, F. culmorum and F. poae in a greenhouse experiment. The fungi were inoculated on winter wheat spikes before or at anther extrusion, or at 8, 18 and 28 days later. Disease levels were estimated by the AUDPC and thousand‐kernel weight (TKW). The fungal biomass (estimated by qPCR) and toxin concentration (deoxynivalenol and nivalenol, estimated by UPLC‐UV‐MS/MS) were measured in each inoculated spike, providing a robust estimation of these variables and allowing correlations based on single‐individual measurements to be established. The toxin content correlated well with fungal biomass in kernels, independently of inoculation date. The AUDPC was correlated with fungal DNA, but not for early and late infection dates. The highest disease and toxin levels were for inoculations around anthesis, but early or late infections led to detectable levels of fungus and toxin for the most aggressive isolates. Fungal development appeared higher in kernels than in the chaff for inoculations at anthesis, but the opposite was found for later inoculations. These results show that anthesis is the most susceptible stage for FHB, but also clearly shows that early and late infections can produce significant disease development and toxin accumulation with symptoms difficult to estimate visually.  相似文献   

18.
Mitogen activated protein (MAP) kinases are key components in signalling networks. In Fusarium graminearum, one of the most devastating fungal plant pathogens, two MAP kinases are known to be involved in pathogenicity, Mgv1 and the Gibberella pathogenicity MAP kinase Gpmk1. ??gpmk1 mutants with a disrupted GPMK1 gene are unable to infect wheat spikelets. They exhibit altered secretion of several extracellular enzymes. Among those, the lipase FGL1 is known to be a major virulence factor of F. graminearum. FGL1 gene expression was decreased in ??gpmk1 strains during wheat head infection. To uncouple FGL1 expression from Gpmk1 activity, we generated ??gpmk1 strains that constitutively express FGL1 under control of the Cochliobolus heterostrophus glyceraldehyde 3-phosphate dehydrogenase (GPD) promoter. The level of extracellular lipolytic activity of these strains in culture was comparable to the wild-type. These mutants showed fully restored conidiation and partial complementation of defects in development that were reported from the ??gpmk1 mutant. They also partially complemented the apathogenic disease phenotype of the ??gpmk1 mutants causing lesions in directly inoculated wheat spikelets. But in contrast to wild-type, their growth was restricted to directly inoculated spikelets. A barrier-like formation was observed at the rachis node. Based on these results, we could show that the lipase FGL1 is necessary but not sufficient to restore complete pathogenicity to the apathogenic ??gpmk1 mutant. Hence, we hypothesize that the MAP kinase Gpmk1 is involved in the regulation of additional factors required for complete virulence of F. graminearum.  相似文献   

19.
The fungal pathogen Fusarium graminearum attacks the seed spikes of barley and wheat, causing sterility, reduced seed weight and accumulation of mycotoxins. To explore infection patterns in barley and in the Arabidopsis model system, the green fluorescent protein gene (gfp) was used to transform F. graminearum. Inoculation of intact barley spikes resulted in rapid colonization of the brush hairs (ovary epithelial hairs) at the extruded seed tip within 7 h. Colonization followed a pattern of rapid basipetal growth along the pericarp epithelium (interior to the lemma and palea), accompanied by slower growth inward through the pericarp and testa. However, at 16 days after infection the aleurone and starchy endosperm remained uninfected, despite heavy colonization of the pericarp. Colonization of the outer lemma also occurred but was much slower. No increase in amylase enzyme activities was found, discounting the possibility that F. graminearum utilizes gibberellin-induced host enzymes to tap the endosperm for nutrients. The transformed Fusarium strain readily infected Arabidopsis thaliana leaves and produced copious spores within distant leaves. Results show the utility of gfp in tracing the growth of this pathogen, without misinterpretation due to contaminating fungi, and for resistance studies utilizing the Arabidopsis model system.  相似文献   

20.
Fungal incidence and mycotoxin contamination of farm-stored maize were assessed and compared in grain samples from three villages each in two agroecological zones over time. Maize samples were collected at 2 and 4 months after stocking from 72 farmers’ stores in 1996 and 1997 in the Humid Forest (HF) and Western Highlands (WHL) of Cameroon. Mycological assays of these samples revealed several fungal species.Nigrospora spp. were the most prevalent fungi in HF (32%) and WHL (30%) in 1996,Fusarium verticillioides (22%) andF. graminearum (27%) were also isolated from these samples. In the WHL in 1996, no significant difference in fungal incidence was found among villages for samples collected 2 months after harvest, but at 4 months incidence was significantly higherP<0.05). In 1997 the levels of fungal contamination were lower than in 1996. The incidence ofAspergillus spp. was low in general, ranging from 0.0 to 5.9% infected kernels. Analysis with thin layer chromatography detected low levels of aflatoxins in a few samples.F. verticillioides mycotoxin fumonisin Bi (300-26,000 ng/g) andF. graminearum metabolites deoxynivalenol (<100–l,300 ng/g) and zearalenone (<50–110 ng/g) were determined by means of polyclonal antibody competitive direct enzyme-linked immunosorbent assay. A significant correlation (r=0.72; P=0.0001) was found between the incidence ofF. graminearum and the contamination with deoxynivalenol. Storage time (2vs 4 months after stocking) had a significant positive effect (r=0.39; P=0.013) on the level of fumonisin B1. This is the first report of the natural occurrence of these mycotoxins in maize in Cameroon.  相似文献   

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