The incidence of Fusarium spp. in stem bases of selected crops of winter wheat in the Midlands, UK

The incidence of pathogenic Fusarium and Microdochium species in stem bases of winter wheat was investigated in a total of nine crops in 3 years, i.e. 1987, 1988 and 1989. Four Fusarium species were isolated: F. nivale ( = Microdochium nivale ), F. avenaceum , F. culmorum and F. graminearum . The predominant species was F. nivale followed by F. avenaceum and F. culmorum . Isolations of F. graminearum were made only from shoots collected during August 1989. The highest incidence of F. nivale occurred during April 1989 in the cultivar Brock when the fungus was isolated from 65% of the shoots sampled. The highest incidence of F. avenaceum was 60% (August 1988, cv. Slejpner) and F. culmorum 37% (August 1989, cv. Mercia). A delay in the isolation of Fusarium spp. during 1987 was attributed to the low January temperatures, and an upsurge of F. culmorum and F. graminearum during 1989 to the warm dry summer. The incidence of F. nivale fluctuated during the 1988 and 1989 seasons, particularly during spring. The effects of fungicide spray programmes and the growth and development of the wheat crop are discussed as possible contributory factors to this.     

Fusarium head blight of cereals in Denmark: species complex and related mycotoxins

Quantitative real-time polymerase chain reaction differentiating 10 Fusarium spp. and Microdochium nivale or M. majus was applied to a total of 396 grain samples of wheat, barley, triticale, oat, and rye sampled across Denmark from 2003 to 2007, along with selected samples of wheat and barley from 1957 to 2000, to determine incidence and abundance of individual Fusarium spp. The mycotoxins deoxynivalenol (DON), nivalenol, zearalenone, T-2, and HT-2 were quantified using liquid chromatography-double mass spectrometry. Major differences in the Fusarium species complex among the five cereals as well as great yearly variation were seen. Fusarium graminearum, F. culmorum, and F. avenaceum were dominant in wheat, with DON as the dominant mycotoxin. F. langsethiae, F. culmorum, and F. avenaceum were dominant in barley and oat, leading to relatively high levels of the mycotoxins T-2 and HT-2. F. graminearum, F. culmorum, and F. avenaceum dominated in triticale and rye. The nontoxigenic M. nivale/majus were present in significant amounts in all cereal species. Wheat and barley samples from 1957 to 1996 exhibited no or very low amounts of F. graminearum, indicating a recent increase of this pathogen. Biomass and mycotoxin data exhibited good correlations between Fusarium spp. and their corresponding mycotoxins under field conditions.     

The use of species-specific PCR-based assays to analyse Fusarium ear blight of wheat

Polymerase chain reaction (PCR) assays for the detection of various Fusarium species and Microdochium nivale subspecies were compared with conventional visual disease assessment using a field plot of wheat in which the central subplot was inoculated with F. culmorum . Visual disease assessment was performed on a range of samples taken from each of 15 subplots at growth stage 80. At harvest, each sample was divided into its component parts, i.e. grain, glume and rachis, and species-specific PCR analysis was used to detect the presence of F. culmorum , F. poae , F. avenaceum , F. graminearum , M. nivale var. majus and M. nivale var. nivale . Within the inoculated subplot there was good correlation between visual disease assessment and PCR analysis, both techniques indicating a high incidence of F. culmorum in this region. According to the visual disease assessment results, there was also a relatively high incidence of F. culmorum in most other regions of the field plot. However, according to PCR analysis the incidence of F. culmorum in many of the other subplots was relatively low and F. poae , M. nivale var. majus and var. nivale , and F. avenaceum were detected within the grain, glume and rachis tissues of many of the ear samples from these subplots. F. poae predominated in the glume component of ears and M. nivale var. majus and var. nivale in the rachis component. M. nivale PCR results revealed that 64% of infected samples involved var. majus , and 36% var. nivale . PCR analysis has highlighted some difficulties that may arise when using visual assessment for studying disease complexes.     

Use of quantitative molecular diagnostic assays to investigate fusarium dry rot in potato stocks and soil

ABSTRACT Specific and sensitive quantitative diagnostics, based on real-time (TaqMan) polymerase chain reaction (PCR) and PCR enzyme-linked immunosorbent assay, were developed to detect dry-rot-causing Fusarium spp. (F. avenaceum, F. coeruleum, F. culmorum, and F. sulphureum). Each assay detected Fusarium spp. on potato seed stocks with equal efficiency. Four potato stocks, sampled over two seed generations from Scottish stores, were contaminated with F. avenaceum, F. sulphureum, F. culmorum, F. coeruleum or a combination of species, and there was a general trend towards increased Fusarium spp. contamination in the second generation of seed sampled. F. sulphureum and F. coeruleum caused significantly (P < 0.05) more disease in storage than the other species when disease-free tubers of potato cvs. Spunta and Morene were inoculated at a range of inoculum concentrations (0, 10(4), 10(5), and 10(6) conidia/ml). Increased DNA levels were correlated with increased disease severity between 8 and 12 weeks of storage. The threshold inoculum levels resulting in significant disease development on both cultivars were estimated to be 10(4) conidia/ml for F. sulphureum and 10(5) conidia/ml for F. coeruleum. To study the effect of soil infestation and harvest date on disease incidence, seed tubers of cvs. Morene and Spunta were planted in a field plot artificially infested with the four Fusarium spp. F. culmorum and F. sulphureum were detected in soil taken from these plots at harvest, and F. sulphureum DNA levels increased significantly (P < 0.05) at the final harvest. All four Fusarium spp. were detected in progeny tubers. There was a trend toward higher levels of F. culmorum detected in progeny tubers at the earliest harvest date, and higher levels of F. sulphureum at the final harvest. The use of diagnostic assays to detect fungal storage rot pathogens and implications for disease control strategies are discussed.     

Development of disease symptoms and fungal pathogens on shoot bases in continuous winter wheat, and effects of fungicides

Field plots in three consecutive crops of winter wheat were sampled at approximately 2-week intervals from April to July in 1989, 1990 and 1991. Culm and stem bases were examined for symptoms of eyespot, sharp eyespot and brown foot rot. The W-type and R-type of Pseudocercosporella herpotrichoides, P. anguioides, Fusarium culmorum, F. avenaceum and Microdochium nivale grown from this plant material on agar were identified. Eyespot was most severe in 1991, when plant development was least rapid following cool weather in late winter and the summer was relatively cool and wet. Sharp eyespot was most severe in 1990, which had a warm summer with moderate rainfall. The other warm summer, 1989, was drier and these conditions favoured late development of brown foot rot, associated mainly with F. culmorum which was scarce at other times. Sharp eyespot sometimes increased where prochloraz, which decreased eyespot, was applied. Distinct symptoms of more than one disease occurred less frequently on the same stem than expected from the individual total occurrences, but co-occurrences of different fungi were often more frequent than expected. In July 1990, Fusarium spp. co-occurred with R-type, but not W-type, P. herpotrichoides more frequently than expected, and in July 1990 and 1991 M. nivale and both W-type and R-type co-occurred more frequently than expected. Fusarium spp. and M. nivale were more frequent, especially in the earlier samples, on nodes than on internodes, whilst P. herpotrichoides normally infected at the internodes. The results suggest that stems weakened or altered by a primary colonizer are often a suitable substrate for a secondary colonizer, often a Fusarium sp., which may begin infection at a distance from the original lesion and often not cause distinct symptoms itself.     

Survey of benomyl resistance in Fusavium species on winter wheat in England and Wales in 1986

In 1986, samples from 109 winter wheat crops in England and Wales were examined for benomyl resistance in Fusarium species. Of the 704 isolates obtained, 581 were identified as Fusarium nivale, of which 92.1 % were resistant to benomyl. Of the remaining isolates, 82 were identified as F. avenaceum, 40 as F. culmorum and one as F. poae; none of these isolates were resistant to benomyl. The vast majority of isolates of Fusarium spp. were obtained from superficial nodal or internodal lesions on the stems.     

甘肃省临夏州小麦脚腐病病原鉴定

对甘肃省临夏州小麦脚腐病病原进行了分离鉴定,从3块病田的37株罹病小麦上分离得到56个真菌菌株,分别被鉴定为雪腐镰刀菌[Fusarium nivale(Fr.)Ces.]、燕麦镰刀菌[Fusarium avenaceum(Corda et Fr.)Sacc.]、麦斑点附球霉[Epicoccum triticiP.Henn.]、小壳色单隔孢菌[Diplodiellasp.]、交链孢菌[Alternariaspp.]、芽枝霉[Cladosporiumsp.]、黑孢霉[Nigrosporasp.]。其中,雪腐镰刀菌致病性最强,燕麦镰刀菌致病性中强,麦斑点附球霉致病性弱,其余菌不致病。     

Fusarium ear blight (scab) in small grain cereals—a review

This review of Fusarium ear blight (scab) of small grain cereals has shown that up to 17 causal organisms have been associated with the disease, which occurs in most cereal-growing areas of the world. The most common species were Fusarium graminearum (Gibberella zeae), F. culmorum, F, avenaceum (G, avenacea), F, poae and Microdochium nivale (Monographella nivalis). The disease was recorded most frequently under hot, wet climatic conditions where significant yield losses and mycotoxin accumulation in grain were reported. Possible sources of inoculum were reported as crop debris, alternative hosts and Fusarium seedling blight and foot rot of cereals. The mode of dispiersal of inoculum to ears remains unclear, but contaminated arthropod vectors, systemic fungal growth through plants, and wind and rain-splash dispersal of spores have been proposed. Infection of wheat ears was shown to occur mainly during anthesis, and it has been demonstrated that fungal growth stimulants may be present in anthers. Despite the importance of the disease, particularly during epidemic years, control methods are limited. Much effort has gone into breeding resistant wheat varieties and into improving our understanding of the possible mechanisms and genetic basis of resistance, with only moderate success. There are also surprisingly few reports of successful fungicidal or biological control of the disease in the field.     

Comparison of commercial European wheat cultivars to Fusarium infection of head and seedling tissue

Susceptibility of eight commercial European wheat cultivars to fusarium head blight (FHB) disease caused by Fusarium graminearum , F. culmorum , F. poae and Microdochium nivale (formerly known as Fusarium nivale ) was compared under controlled environment conditions (16°C). FHB did not differentially affect cultivars in terms of disease symptoms, fungal DNA content of grain or deoxynivalenol (DON) contamination. However, the Hungarian-grown cultivars GK-Othalom and Fatima 2 (of Romanian origin) showed greater type V resistance (yield tolerance) to FHB than did the others. Also, nivalenol was produced by F. poae in these two cultivars and in Italian cultivar Norba, but not in other cultivars. Overall, significant relationships were found between the FHB and seedling blight resistance in vitro of these eight cultivars, but such relationships were generally highly dependent on cultivar, and therefore it is likely that the in vitro test is at best measuring components of FHB resistance and/or genotype-specific resistance components.     

Visual disease and PCR assessment of stem base diseases in winter wheat

Stem base disease (eyespot, sharp eyespot and brown foot rot) was assessed visually and by the polymerase chain reaction (PCR) technique on single plants sampled at four-week intervals in two crops of winter wheat grown in the UK in 1992–3. PCR assays were conducted for Fusarium avenaceum , F. culmorum , both varieties of Microdochium nivale , both eyespot-causing species of Tapesia and Rhizoctonia cerealis . PCR diagnoses were compared with visual diagnoses at each time point. Eyespot was caused principally by T. acuformis (R-type) and developed rapidly late in the season. Visual diagnoses of eyespot were largely confirmed by PCR but T. acuformis was detected in many plants lacking eyespot symptoms. R. cerealis was detected at relatively low incidences on both sites, and sharp eyespot visual diagnoses did not correlate with the incidence of any of the pathogens assayed by PCR. Brown foot rot, caused principally by Microdochium nivale var . majus , accumulated earlier in the season than eyespot. Overall, visual diagnoses of stem base disease coincided poorly with PCR data until after growth stage (GS) 30.     

Restriction fragment length polymorphism analysis of variation in Fusarium species causing ear blight of cereals

Genetic variation in Fusarium species on wheat was investigated using restriction fragment length polymorphism (RFLP) analysis. Single-spore lines (76) of Fusarium were recovered from 24 ears of wheat in a field plot exhibiting severe symptoms of Fusarium ear blight and identified using classical taxonomic criteria. Four Fusarium species were present, of which F. avenaceum and F. culmorum were predominant with F. lateritium and F. poae present in two ears and one ear, respectively. RFLP analysis using rDNA (pTA71) or total genomic DNA from an F. culmorum isolate clearly distinguished the four species. Genetic fingerprints of the isolates generated using DNA of bacteriophage M13 (which contains a mini-satellite repeat sequence) revealed considerable variation within three of the four species (except F. poae). Generally, only a single clone was recovered from each ear and in all but one case only a single species was obtained from each spikelet. However, in several instances it appeared that more than one clone of a species was present within a single spikelet.     

Characterization of Fusarium spp. responsible for causing dry rot of potato in Great Britain

A 3-year survey was undertaken to establish the relative frequency of different Fusarium spp. present as inoculum on potato tubers collected from four regions of Great Britain. A total of 219 samples (comprising 10 950 tubers) were collected from the 2000, 2001 and 2002 crops and processed to recover dry rot-producing isolates. In total, 228 isolates of Fusarium spp. were recovered. Most (94·7%) of these isolates were attributed to one of four Fusarium species: F. coeruleum, F. avenaceum, F. culmorum and F. sambucinum (formerly F. sulphureum) . The incidence of the combined Fusarium spp. increased the further south the crops had been grown. Fusarium coeruleum was the most commonly isolated species in each survey year, comprising 37 to 52% of the total Fusarium species. Selected isolates of each species were evaluated for their ability to produce rots in potato tubers. Fusarium sambucinum was a more aggressive pathogen than the other Fusarium species in eight out of 10 cultivars. Fusarium avenaceum and F. culmorum were relatively weaker pathogens. However, these species were aggressive on some cultivars, notably Hermes. The selected isolates were also assessed for their sensitivity to the fungicides thiabendazole and imazalil. Using in vitro tests, 65% of F. sambucinum isolates were resistant to thiabendazole and 7% of F. avenaceum isolates were resistant to imazalil. Tubers treated with imazalil yielded a higher proportion of isolates of F. avenaceum than those that were untreated. Similarly, a higher proportion of F. sambucinum isolates were recovered from tubers treated with thiabendazole than from those that were not treated.     

大豆根腐病原镰孢菌种群多样性DGGE分析及其致病性研究

 应用变性梯度凝胶电泳(DGGE)技术以及主成分分析方法,结合植物病原菌传统分离、鉴定及致病力测定,检测位于黑龙江省海伦市大豆连作定位试验区根腐病原镰孢菌的种群构成及其致病力。采用真菌传统分离和鉴定方法共确定镰孢菌6个种,包括燕麦镰孢Fusarium avenaceum、木贼镰孢F. equiseti、禾谷镰孢F. graminearum、腐皮镰孢F. solani、尖镰孢F. oxysporum和拟轮枝镰孢F. verticillioides。其中,尖镰孢菌的分离频率最高,为56.7%。结合DGGE条带克隆测序及系统发育分析鉴定出8种镰孢菌,较传统方法增加了黄色镰孢F. culmorum和一个尖镰孢近似种。同时,DGGE图谱中尖镰孢所占百分比下降为37.4%。采用主成分分析方法将大豆生育指标相关的多种变量进行降维分析,得到第一主成分贡献值为91.2%。按照贡献值的正负结果,将30株镰孢菌分为致病和非致病类群。第二主成分贡献值为5.8%,根据其正负值可以矫正被错误估计的致病能力。综合所有研究结果,该定位试验区大豆根腐病主要病原镰孢菌为尖镰孢、禾谷镰孢和燕麦镰孢,且以尖镰孢菌为优势病原菌。     

Stem-base disease and fungal colonisation of winter wheat grown in compost inoculated with Fusarium culmorum, F. graminearum and Microdochium nivale

Fungal colonisation of winter wheat cv. Cadenza by Fusarium culmorum, F. graminearum and Microdochium nivale was studied under conditions designed to avoid the splash dispersal of conidia from infested compost, to evaluate the possibility that systemic growth may transfer infection from the stem-base to the head. At decimal growth stages 33, 59, 77–87 and 95 the extent of fungal growth was assessed using a sample of 72 plants, by the recovery of fungal species from the stem-base, from each node and from the ear. Each of the fungi was recovered from stem tissues above soil level in some, apparently symptomless, plants. Symptoms of Fusarium foot rot were seen in an increasing proportion of plants during grain-fill and desiccation. There was an inverse relationship between recovery and the height above stem-base from which the stem tissue was excised. F. culmorum was the most frequently isolated fungus and it was also recovered from the highest position in plants. Only 3% of plants were colonised above the second node and none of the fungal species were recovered from either the fifth node or the ear. This suggests that colonisation and systemic growth from Fusarium infested compost is unlikely to contribute to the development of ear blight symptoms in winter wheat.     

Zearalenone production in Fusarium culmorum after transformation with DNA of F. graminearum

Total DNA from a cycloheximide-resistant mutant of Fusarium graminearum producing zearalenone was incubated with the protoplasts of a non-zearalenone-producing cycloheximide-susceptible isolate of F. culmorum. The regenerated protoplasts were inoculated on a 5-mM cycloheximide medium. The cultures which developed were examined for zearalenone production. Sixty-five cycloheximide-resistant isolates, including two isolates producing zearalenone, were obtained from approximately 3.6 × 10⁴ viable F. culmorum protoplasts. Similar incubations with homologous F. culmorum DNA and non-fungal DNA did not elicit zearalenone production. The results suggest the transformation of F. culmorum by the genetic factors responsible for cycloheximide resistance and zearalenone production from F. graminearum. The epidemiological and taxonomic significance of these observations is discussed.     

Towards the Development of a Novel In Vitro Strategy for Early Screening of Fusarium Ear Blight Resistance in Adult Winter Wheat Plants

A novel in vitro bioassay is described for screening Fusarium ear blight (FEB) resistance in adult winter wheat plants. Seven winter wheat cultivars were assessed for components of partial disease resistance as 28 day-old detached leaf segments in the laboratory using isolates of Microdochium nivale var. nivale and M. nivale var. majus. Results were compared with disease data obtained at anthesis using the same cultivars as whole plants and the same isolates under glasshouse conditions. Significant cultivar differences were observed using detached leaves, with cv. Avalon (a Fusarium culmorum ear susceptible cultivar) having the shortest leaf incubation period, greatest leaf lesion development and shortest leaf latent period compared to cv. Spark (a Fusarium culmorum ear resistant cultivar), which had the longest leaf incubation period, least leaf lesion development and longest leaf latent period. Using whole plants, cv. Avalon had the shortest ear incubation period and greatest ear disease severity, whilst cv. Spark had the longest incubation period and least ear disease severity. Overall, cultivars of intermediate F. culmorum ear resistance expressed intermediate responses to M. nivale isolates, using both detached leaves and whole plants. Significant correlations were found with ear disease severity and ear incubation period in whole plants and components of partial disease resistance in detached leaves, with significant correlations obtained between leaf incubation period and ear disease parameters using the M. nivale var. nivale isolate. In addition, leaf latent period and leaf lesion size showed significant correlations with whole plant reactions using M. nivale var. nivale and var. majus isolates. The in vitro screening of cultivars as detached leaves using M. nivale isolates may offer a real possibility of a rapid bioassay for the early screening of FEB resistance in wheat and other cereals.     

Isozyme and RAPD-PCR analyses of Fusarium avenaceum strains from Finland

Differences in isozyme and RAPD-PCR polymorphisms amongst 33 isolates of Fusarium avenaceum were compared using native polyacrylamide gel electrophoresis and agarose gel electrophoresis. The isolates were collected from different regions of Finland. Amongst eight enzymes analysed clear isozyme polymorphism was detected in five enzymes which could be grouped into 20 different electrophoretic phenotypes and three main groups at the similarity level of 70% in unweighted pair group method with arithmetic average (UPGMA) analysis. RAPD-PCR analysis differentiated all F. avenaceum strains from each other. The phenotypes resulting from RAPD-PCR analysis were grouped into five main groups by UPGMA analysis at the similarity level of 55%. These main groups had several similarities with the main groups from isozyme analysis. RAPD-PCR patterns of 16 isolates of Fusarium graminearum F. culmorum F. equiseti F. oxysporum and F. redolens were also studied and strains from each Fusarium species formed individual groups in UPGMA and principal components analyses. Thus, the extent of isozyme and RAPD-PCR polymorphisms found in Fusarium strains potentially provides a method for identifying the fungi both at strain and species level.     

Suppression of wheat-seedling diseases caused by Fusarium culmorum and Microdochium nivale using bacterial seed treatment

Snow mould, caused by Microdochium nivale , and seedling blight caused by members of the Fusarium complex, are cereal diseases of great economic importance in many temperate zones. In a glasshouse bioassay designed to enhance disease, about 600 plant-associated bacterial isolates obtained by different methods were screened for suppressive effects in wheat against infection caused by Fusarium culmorum . Although most of the isolates tested had a neutral effect on test plants and disease development, a few were synergistic to the pathogen and about one-fifth showed > 80% disease suppression. During five consecutive growing seasons, 164 bacterial isolates were tested in field experiments against both F. culmorum and M. nivale as causal agents of seedling blight. Tests for effects on yield in experiments with spring and winter wheat, performed in different climatic regions of Sweden, showed that disease-suppressive effects were repeatable. The most efficient isolates, three fluorescent pseudomonads and a species of Pantoea , suppressed disease equal to that of the fungicide guazatine, both with respect to crop stand and yield. Seed treatment with Pantoea sp. (isolate MF 626) increased yield by an average of more than 500 kg ha⁻¹ in six field experiments.     

小麦赤霉病流行区镰刀菌致病种及毒素化学型分析

 为从分子水平上明确小麦赤霉病流行区镰刀菌致病种及其B 型毒素化学型的分布特点,本研究对2008 年度采自四川、重庆、湖北、安徽、江苏、河南6 省33 县市的赤霉病穗上分离获得的433 个镰刀菌单孢菌株,用鉴定种和鉴定B 型毒素化学型的特异性引物进行了鉴定分析。致病种检测结果表明,四川病穗检测到Fusarium asiaticum、F. graminearum、F.avenaceum 和F. meridionale 4 个镰刀菌种,重庆、湖北、安徽和江苏病穗检测到F. asiaticum 和F. graminearum 2 个种,河南病穗仅检测到F. graminearum 1 个种。毒素化学型检测结果表明,Nivalenol(NIV)是四川和重庆镰刀菌主要毒素化学型,Deoxynivalenol(DON)是湖北、河南、安徽和江苏镰刀菌主要毒素化学型;将DON 化学型进一步划分为3-AcDON 和15-AcDON 显示,四川、湖北、江苏镰刀菌毒素以3-AcDON 为主,安徽镰刀菌毒素为3-AcDON 和15-AcDON 两者参半,河南镰刀菌全部产生15-AcDON。结果揭示,F. asiaticum 是四川、重庆、湖北和江苏等赤霉病流行麦区的优势致病种;镰刀菌产生的DON 和NIV 毒素化学型存在明显的地域分布,长江上游的麦区以NIV 为优势化学型,长江中下游麦区以DON 为优势化学型;镰刀菌致病种与DON 毒素的化学型间存在一定关系。     

Relationship between the fungal complex causing Fusarium head blight of wheat and environmental conditions

ABSTRACT Over 4 years, the environmental conditions and the causal agents of Fusarium head blight (FHB) disease of wheat were determined in field sites in four European countries: Hungary, Ireland, Italy, and the United Kingdom. Polymerase chain reaction-based methods were used to detect each species causing FHB and quantify its DNA (as a measurement of fungal abundance) in the samples. Canonical correspondence analysis (CCA) was used to determine the relationship of the incidence and abundance of each species with weather variables. CCA indicated that little variability in the species prevalence data was explained by the weather variables. In contrast, a greater proportion of variability in abundance data was accounted for by the weather variables. Most samples contained two or more species and statistical analysis suggested that these species tended to coexist at field sites. CCA also indicated that there were differences in the relationships of the prevalence and abundance of the six FHB species with environmental variables. Fusarium poae was associated with relatively drier and warmer conditions, whereas F. graminearum was associated with warmer/humid conditions. F. avenaceum and F. culmorum were both associated with niches of cooler/wet/humid conditions. Two Microdochium species were associated with regions of relatively cool/moderate temperatures and frequent rainfalls of short duration. The results also suggested that environmental conditions differentially affect the infection and colonization processes, and the comparative abundance of the six species.