Graminearum Group Research Articles

Fungal communities in wheat grain show significant co-existence patterns among species

The wheat grain mycobiome is only scarcely investigated and focus has been on seed-transmitted wheat pathogens of agricultural importance. In this study, we used next generation sequencing to study the mycobiome of Danish wheat grain samples at harvest. In total 228,421 sequences were obtained from 90 samples that were taken from locations across Denmark during three years. These sequences could be grouped into 173 non-singleton operational taxonomic units (OTUs) of which 21 OTUs, identified as belonging to genera such as Fusarium, Alternaria, Cladosporium. Phaeosphaeria and Microdochium, were identified as ‘core’ OTUs as they were found in all or almost all samples and accounted for almost 99 % of all sequences. The remaining OTUs were only sporadically found and only in small amounts. Cluster and factor analyses showed patterns of co-existence among the core species. Cluster analysis grouped the 21 core OTUs into three clusters: cluster 1 consisting of saprotrophs, cluster 2 consisting mainly of yeasts and saprotrophs and cluster 3 consisting of wheat pathogens. Principal component extraction showed that the Fusarium graminearum group was inversely related to OTUs of clusters 1 and 2.

Gibberella zeae on St. John's wort in Serbia

Gibberella zeae (anamorph Fusarium graminearum) was determined on seed of St. John's wort produced in localities Pančevo, Gorobilje and Kačarevo during 2008 and 2009. Morphological characteristics of monosporial isolates were described. All tested isolates formed in vitro perithecia, and were classified as F. graminearum (syn. F. graminearum Group 2). Pathogenicity was confirmed by the artificial inoculation of St. John's wort seed.

Presence of deoxynivalenol in small-grain samples from 2009/10 harvest season

Fusarium head blight (FHB) is present in all growing regions of small grains and causes significant losses in yield and grain quality. In our environmental conditions, dominant species is Fusarium graminearum Group 2. During 2009/10 there was a significant Fusarium infestation on wheat, barley and triticale. The aim of this study was to examine the contents of deoxynivalenol (DON) in cereal samples taken after 2009/10 harvest season. We analyzed 22 NS varieties of small grains from Rimski Sancevi, including 16 varieties of winter wheat, one facultative wheat variety, four varieties of winter barley and one variety of triticale. Analytical methods based on clean-up by solid-phase extraction (SPE) columns and detection by liquid chromatography were used. Fifteen out the 22 analyzed samples were positive for the presence of DON at a mean level of 0.537 mg/kg. The highest concentration was 1.952 mg/kg. These findings were in correlation with percentage of the Fusarium damaged kernels.

Incidence of Crown Rot Disease of Wheat Caused by Fusarium pseudograminearum as a New Soil Born Fungal Species in North West Iran

Root rot and crown rot is one of the main important fungal diseases on wheat in North West Iran. The disease was studied during 1999-2004 growing seasons in four provinces including Qazvin, Zanjan, East Azarbyjan and Ardabil. Different wheat fields in the areas studied were visited and samples of the plants showing symptoms like chlorosis, withering, whiting of spikes, growth reduction and white heads were collected and transferred to the laboratory. Samples were surface sterilized with sodium hypochlorite and then cultured on common media (PDA) and specific media (PPA and CLA). Totally 155 fungal isolates belonging to five genera were identified and the pathogen most frequently isolated was Fusarium pseudograminearum (formerly known as F. graminearum Group 1). This species normally causes crown rot resulting in severe damage in several locations under dry spring conditions. The disease caused losses from 18-45.5% in the fields where the season and crop rotation allowed the disease to build up. Prolonged moisture stresses coupled with relatively high soil temperature in the fall enhanced early disease development on the roots and sub crown internodes. Environmental conditions and genetic susceptibility of cultivars were the two main factors affecting diseases incidence.

Production of zearalenone, deoxynivalenol, nivalenol, and acetylated derivatives by Australian isolates of Fusarium graminearum and F.pseudograminearum in relation to source and culturing conditions

Australian isolates of Fusarium pseudograminearum (Fp = F. graminearum Group 1) and F.�graminearum (Fg = F. graminearum Group 2) can produce mycotoxins including zearalenone (ZEA), 4-deoxynivalenol (DON), and nivalenol (NIV). Fp isolates from wheat and barley tillers in southern Queensland all produced ZEA and DON in culture, and one typical isolate also produced 3-acetyldeoxynivalenol. Most Fg isolates from wheat and sorghum grains in southern Queensland produced ZEA and DON and one typical isolate also produced 15-acetyldeoxynivalenol. Fg isolates from maize plants in northern Queensland were all ZEA and NIV producers, which was consistent with previous reports, and they also produced high concentrations of acetyl-nivalenols. ZEA and either DON or NIV production by cultures derived from different conidia (and ascospores in Fg isolates) varied by 4–18-fold for ZEA and 2–4-fold for DON/NIV production, and there were significant negative correlations between ZEA and either DON or NIV, indicating a common controlling process. The pattern of ZEA production was quite different between Fp and Fg, with ZEA production being relatively delayed in Fg. After 7 days incubation at 28�C on maize meal, one Fp isolate produced 49 mg ZEA/kg, but in both DON-producing and NIV-producing isolates of Fg, ZEA concentrations after 7 days were <1 mg/kg. ZEA and DON were produced on sorghum and combined wheat–barley grains as well as maize meal, although there were trends for maize meal to be more productive, probably due to greater surface area or different gaseous exchange. Low temperature incubation of a Fg DON-type isolate increased ZEA production, but did not affect either a Fg NIV-type isolate or a Fp isolate. Relationships between these patterns of mycotoxin production, pathogenicity, and implications for crop contamination are discussed.

Climatic analysis of the distribution of Fusarium graminearum, F. pseudograminearum and F. culmorum on cereals in Australia

The distributions of Fusarium graminearum (Gibberella zeae), F. pseudograminearum (F. graminearum Group 1) and F. culmorum from cereals in Australia were determined from published survey data and accessions to culture collections. The distributions were analysed in terms of climate, using the climate matching system BIOCLIM. F. graminearum was found mostly in warm temperate to subtropical areas with moderate to high summer rainfall, where mean temperature of the warmest quarter was greater than 18.7°C and rainfall of the warmest quarter was greater than 195 mm. This appeared to be due to the effect of climate on production of maize, the host from which most records were obtained. F. pseudograminearum occurred throughout the main cereal growing areas and its occurrence did not appear to be limited by climate within the Australian grain belt. The distribution of F. culmorum on cereals was more limited than that of F. pseudograminearum. In the southern winter rainfall zone, F. culmorum was restricted to sites with mean summer temperatures less than about 22°C and annual rainfall greater than about 350 mm, whereas in the northern summer rainfall zone F. culmorum was restricted to areas with mean summer temperatures less than about 24.5°C and annual rainfall greater than about 625 mm.

The application of species-specific assays based on the polymerase chain reaction to analyse Fusarium crown rot of durum wheat

Crown rot of wheat in Australia is caused by species of Fusarium, particularly F pseudograminearum, formerly known as F. graminearum Group 1. Rapid assays are required to identify the species responsible for disease symptoms, especially those with similar morphology. Previously developed assays based on the polymerase chain reaction (PCR) were able to identify F. pseudograminearum, F. graminearum, F. culmorum and F. crookwellense isolates, but not F. acuminatum. To design novel F. acuminatum and F. pseudograminearum species-specific primer sets, randomly amplified polymorphic DNA profiles were amplified that differentiated F. acuminatum and F. pseudograminearum from the other species and polymorphic bands were cloned and sequenced. The specificity of the PCR assays was verified on 79 isolates from 12 different Fusarium species. For two isolates an apparent misidentification occurred using the F. pseudograminearum PCR assay. These isolates were fingerprinted using Amplified Fragment Length Polymorphism analysis, which showed that they had genotypes more similar to F. graminearum than F. pseudograminearum. The PCR-based assays were validated using seedlings infected with single or multiple isolates. A method was also devised to rapidly identify Fusarium species associated with crown rot symptoms on mature wheat stems by culturing the fungi and extracting DNA directly from infected tissue. This assay can be used for routine diagnosis and for epidemiological studies of this disease.

Seedling Blight Development and Control in Spring Wheat Damaged by Fusarium graminearum Group 2.

Aspects of seedborne infection in Fusarium-damaged and undamaged seed lots of hard red spring wheat were studied. In a 22°C environment, seedling blight developed from plantings of Fusarium-damaged seed that were characterized by both reduction and delay in emergence and postemergence seedling death. After 28 days, stand counts from the Fusarium-damaged seed lot averaged 46%, compared with 98% from the undamaged seed lot. However, the mean dry weight of surviving seedlings from the Fusarium-damaged lot was not statistically different from that of seedlings from the undamaged seed lot. Surface-sterilization reduced recovery of Fusarium graminearum group 2 from the damaged lot by 7% and increased germination by 32%, suggesting that seed are both infected and contaminated with viable propagules of the fungus. In field experiments, seed treatment with maneb- or thiabendazole-containing fungicide combinations significantly reduced seedling blight and improved stands derived from the Fusarium-damaged seed lot. Triazole fungicides, including difenoconazole, fenbuconazole, and tetraconazole, were less effective. Triazole fungicides and carboxin-containing fungicide combinations controlled loose smut in these trials, while maneb seed treatments did not. In four field tests, seedling blight incidence in plantings of Fusarium-damaged seed increased as soil temperatures during emergence increased. The distribution of blighted seedlings was random and not clustered. Seedling blight did not develop in field plantings of the undamaged seed lot.

Isozyme characterisation of Fusarium graminearum isolates associated with head blight of irrigated wheat in South Africa

Head blight, caused by certain species in the genus Fusarium, has become an economically important disease of wheat under centre pivot-irrigation along the Orange River region in South Africa. Isozyme analysis, by means of starch gel electrophoresis, was employed to compare 73 Fusarium isolates, obtained from three farms in this region, with isolates of Fusanum acuminatum, F. chlamydosporum, F. compactum, F. crookwellense, F. culmorum, F. equiseti, F. graminearum Group I and Group II. F. moniliforme, F. oxysporum, F. solani, and F. subglutinans. For all 11 Fusarium species, nine loci were identified in eight enzyme systems and 19 electrophoretic phenotypes (EPs) were detected, each composed of isolates from one species only. The extent of isozyme polymorphisms found among these Fusarium spp. provides a potential method for delineating isolates at species level. Six EPs, of which the most common one comprised 36 isolates, were identified within isolates obtained from the three farms. These isolates clustered together with the F. graminearum Group II reference isolates. Based on perithecial production, their identity was confirmed as F. graminearum Group II.

Morphological and molecular characterization of Fusarium pseudograminearum sp. nov., formerly recognized as the Group 1 population of F. graminearum

Fusarium pseudograminearum sp. nov., formally known as F. graminearum Group 1, is described and illustrated. Fusarium pseudograminearum can be distinguished from F. graminearum based on difference in colony growth rates, region of conidia with greatest width, different reactions to near-ultraviolet black-light-blue light concerning the length of 3-and 5-septate conidia, and absence of homothallic production of perithecia. Maximum parsimony analysis of DNA sequences from the β-tubulin gene introns and exons indicate that F. pseudograminearum represents a phylogenetically distinct species that is a sister group to a F. graminearum-F. lunulosporum-F. culmorum clade. DNA sequence data from the translation elongation factor gene were used to develop a polymerase chain reaction primer pair which specifically amplified DNA from all isolates of Fusarium pseudograminearum tested.

Morphological and Molecular Characterization of Fusarium pseudograminearum sp. nov., Formerly Recognized as the Group 1 Population of F. graminearum

Fusarium pseudograminearum sp. nov., formally known as F. graminearum Group 1, is described and illustrated. Fusarium pseudograminearum can be distinguished from F. graminearum based on difference ...

Effect of Burkholderia (Pseudomonas) cepacia and soil type on the control of crown rot in wheat

A rifampicin-resistant isolate of Burkholderia (Pseudomonas) cepacia (A3R) reduced crown rot (Fusarium graminearum Group 1) symptoms significantly (P ≤ 0.05) in wheat in glasshouse and field experiments and increased grain yield significantly (P ≤ 0.05) in one of two field experiments. In glasshouse experiments, applying the bacteria as a soil drench (2.5 × 109 cfu/g soil) was more effective than coating the bacteria on wheat seed (3.4 × 107cfu/seed). In field experiments, the bacteria were applied as a soil drench at the rate of 1.8 x 1010 cfu/m row. In both the glasshouse and the field, disease severity in the bacteria-inoculated treatments was significantly less in a silt loam than in a sandy loam. The silt loam had a large proportion of fine clay and silt particles (51.7%), which may have favoured the biocontrol activity and survival of the introduced B. cepacia. In a glasshouse experiment, control by B. cepacia was significantly greater in the silt loam than in the sandy loam, which in turn was greater than in a loamy sand. The loamy sand appeared to favour crown rot development but not the activity or survival of the bacterial antagonist. The latter was reflected by the relative populations of the rifampicin-resistant bacteria re-isolated from the various soils during a 5-week period after application of the bacteria (silt loam > sandy loam > loamy sand). This study further confirms that soil type can influence the populations and the level of biocontrol activity of some bacterial antagonists.

Crown rot and common root rot in wheat grown under different tillage and stubble treatments in southern Queensland, Australia

In southern Queensland, crown rot caused by Fusarium graminearum Group 1 and common root rot caused by Bipolaris sorokiniana are common soilborne diseases of wheat and barley. The incidence of these diseases was measured in the susceptible wheat ( Triticum aestivum L.) cultivar, Hartog which was grown under no tillage, reduced tillage (two tillage operations plus herbicides) and where stubble was retained or removed by burning (1984–1986) or physically removed (1987–1993). Primary tillage was with blade, disc or chisel implements. The level of crown rot and common root rot was higher where stubble was retained than where it was removed. There was a significant interaction in incidence of crown rot between stubble management and some types of tillage. Where there was no tillage, incidence of crown rot was significantly higher where stubble was retained (32.2%) than where it was removed (4.7%) whereas under disc tillage, there was no significant difference in disease level between stubble treatments (12–17%). Incidence of crown rot was not affected by the type of tillage employed. The incidence of deadheads (heads without grain) caused by crown rot was lowest in the no tillage plots (4.3%) and highest in the reduced (19.3%) and conventional (12.2%) disc tillage stubble retained treatments. Available soil water (depth of 1.2 m) at sowing and anthesis was lowest in the conventional disc stubble retained plots and highest in the no tillage stubble retained plots. It is hypothesised that the high levels of deadheads were due to moderate to high levels of disease and low available soil water at planting and anthesis. Although incidence of crown rot was high under no tillage, incidence of deadheads was lower than in other treatments due to the higher availability of soil water. Severity of common root rot was lower in stubble removed, than in stubble retained, treatments and also lower in no tillage than in any of the other tillage treatments.

Pathogenic Fungi Associated with Fusarium Foot Rot of Winter Wheat in the Semiarid >Pacific Northwest

Winter wheat plants and soil were collected from 288 nonirrigated fields in the semiarid Pacific Northwest during 1993 and 1994. Fungi associated with 5,390 crown and subcrown internodes from 10 Oregon and nine Washington counties were identified. Fusarium graminearum Group 1 was most widespread and the dominant pathogen associated with a crown and root rot named Fusarium foot rot or dryland root rot. E culmorum was widely distributed in soil but was detected in plants in only half as many locations as F. graminearum. Other pathogens included Bipolaris sorokiniana, Microdochium nivale, and F. avenaceum. Highly variable isolation frequencies for all five pathogens were presumed related to a very dry and a very wet survey year. Each pathogen was considered dominant or co-dominant at one or more sites during one or more years. All five species and F acuminatum and F. oxysporum included isolates capable of killing wheat seedlings in the greenhouse.

Control of Fusarium crown rot of wheat by late stubble burning and rotation with sorghum

The effects of late (autumn) burning of stubble, and of rotation with sorghum, on the incidence of infection of wheat with Fusarium graminearum Group 1 were studied under conditions simulating commercial practice. Late stubble burning was effective in maintaining a low incidence of infection over four seasons, compared with stubble retention. This did not result in increased yield, possibly because of deleterious agronomic effects of removing residue. Incidence of infection was significantly lower in wheat rotated with sorghum than in continuous wheat, over three complete rotation cycles.

White crown rot - a new disease of cereals

A new cereal disease was observed in central New South Wales in 1990 and 1991. The most characteristic symptoms were the formation of whiteheads and the presence of profuse white mycelium enveloping tiller bases in the crown region of infected wheat plants. Sometimes, black zone lines were present in the white mycelium. An unidentified sterile basidiomycete was consistently isolated from the tiller bases and shown to be the causal agent in pot and field experiments. The fungus was pathogenic to wheat, barley and triticale. The disease has been named ‘white crown rot’ to distinguish it from crown rot caused by Fusarium graminearum Group 1, which is renamed ‘Fusarium crown rot’.

Mycogeography of Fusarium species in soils from tropical, arid and mediterranean regions of Australia

Twenty-two Fusarium species as well as three undescribed populations were recovered from 42 sites representing three different climatic regions: Darwin (tropical), Alice Springs (arid) and Ceduna (mediterranean). These species were F. acuminatum subsp. acuminatum, F. anthophilum, F. avenaceum subsp. aywerte, F. beomiforme, F. chlamydosporum, F. compactum, F. dimerum, F. equiseti, F. graminearum Group 1, F. lateritium, F. longipes, F. merismoides, F. moniliforme, F. napiforme, F. nygamai, F. oxysporum, F. polyphialidicum, F. proliferatum, F. semitectum, F. scirpi, F. solani, F. subglutinans . Fifteen species were recovered from soils from the tropical region, 13 species and three undescribed populations from the arid region and seven species from the mediterranean region. Species found in all three regions were F. dimerum, F. equiseti, F. solani and F. oxysporum . Species recovered only from tropical soils were F. beomiforme, F. longipes, F. moniliforme and F. subglutinans. F. nygamai and F. scirpi were only recovered from arid soils; and F. a. acuminatum was only recovered from the mediterranean region. F. chlamydosporum and F. compactum were isolated frequently from soils in the tropical and arid regions but were more abundant in the arid soils from Alice Springs.

Reaction of Durum Wheat Cv Yallaroi to Crown and Root Rot Caused by Fusarium Graminearum Group 1 and Fusarium Crookwellense

The comparative pathogenicity of Fusarium graminearum Group 1 and Fusarium crookwellense to the durum wheat cv. Yallaroi was studied in the greenhouse. F. graminearum Group 1 was shown to cause more severe above ground symptoms of crow rot and a higher incidence of infection than F. crookwellense at all the sampling dates. F. crookwellense did, however, cause some root and crow necrosis.

Effect of rotation with barley and oats on crown rot of wheat in the northern wheat belt of New South Wales

We investigated the incidence of Fusarium graminearum Group 1 (infection, stem colonisation) and crown rot in 3-year crop sequences of 1 or 2 years of barley, oats, or mown oats followed by wheat, compared with 3 years of wheat. Seed was sown into the stubble of the previous crop. Stubble production was estimated for each cereal treatment. Plants of each cereal were infected by the crown rot pathogen. Oats were susceptible to infection but did not express symptoms of crown rot in 2 years of the trial. Oats can, therefore, be considered a symptomless host that may contribute to the maintenance of inoculum. The overall mean incidence of infected plants increased from 12% in 1987 to 81% in 1989. The various treatments did not significantly reduce the incidence of infected wheat plants in November of the final year. The incidence of crown rot of wheat in 1989 was greatest after 2 prior wheat crops and lowest after 1 or 2 years of mown oats. The 3 species produced a similar amount of straw by weight; however, mown oats produced significantly less. Oat straw decomposed more rapidly than that of other cereals in controlled conditions.

Reaction of Australian cultivars of oats and barley to infection by Fusarium graminearum Group 1

The incidence of infection by Fusarium graminearum Group 1 and the incidence of crown rot were compared for various cultivars of oats, wheat and barley in glasshouse and field experiments. In glasshouse studies, the incidence of infected plants was lower in oats than in wheat or barley at 6 weeks after sowing. Crown rot symptoms were not observed in oats of any cultivar. The incidence and severity of crown rot in barley was similar to that in wheat cv. Banks. Between 17 and 29 genotypes of oats, wheat and barley were assessed in field trials over 3 years. Stem browning, a symptom of crown rot, was common in wheat and barley but was not observed in any cultivar of oats. Among plants of wheat and barley, the effect of cultivar on incidence of crown rot was significant (P = 0.05) in 3 of 4 trials. Results suggest that oats are a symptomless host. This should be considered when growing oats in rotation to reduce crown rot inoculum. The barley cultivars assessed all developed moderate-severe crown rot symptoms and thus may incur yield limitations where crown rot is prevalent.