POPULATION DIFFERENCES IN INDIGENOUS FUSARIUM SPECIES BY CORN CULTURE OF PRAIRIE SOIL

Six species of Fusarium were identified among approximately 7,000 cultures isolated from roots and soils collected from prairies and cornfields in southern Minnesota. In both soil sources, F. oxysporum and F. solani predominated, followed in order by F. roseum, F. episphaeria, F. tricinctum, and F. moniliforme. The same order was obtained for the 28 species of prairie grasses and forbs as for corn. From prairie plant and corn roots, respectively, F. oxysporum was isolated from 64 and 90%; F. solani, 26 and 80%; F. roseum, 8 and 35%; and F. tricinctum, 6 % each. In 10 of 17 companion soil pairs, populations of Fusarium species were higher in cornfield than in prairie soils. Populations of F. roseum and F. moniliforme especially, were higher in cornfield soils of sample pairs, but populations of F. solani were higher in prairie soils. Fusarium roseum ‘Equiseti’ was the predominant cultivar of this species in both prairie and cornfield soils. Thus all six species of Fusarium appeared to be indigenous to the prairie, and some, especially F. roseum, apparently had increased in prevalence in soil and roots by corn culture.     

Distribution of Fusarium in some British soils

Soil fusaria from various areas in and around Surrey were estimated on medium selective forFusarium. 4 species ofFusarium, F. episphaeria. F. oxysporum, F. roseum andF. solani were detected.F. roseum was the most widely distributed species and present in highest numbers. Among 3 cultivars of this species obtained, non-pathogenic clones of “Culmorum” was always present. The other 3 species ofFusarium were less widely distributed and occurred in lower numbers, withF. solani being the most restricted in distribution and present in very small populations. NoFusarium was recorded for soils from natural field vegetation (except grass areas) and forests.     

Moniliformin production byFusarium species isolated from Argentinian corn

Forty-one isolates ofFusarium obtained from the main Argentinian corn production area were tested for their ability to produce moniliformin. One of 22 isolates ofF. moniliforme, 2/10 of F.proliferatum and 3/9 ofF. subglutinans, produced moniliformin in a range between 0,3 to 2,7 mg/g. These data represent the first report of the production of moniliformin byFusarium species from section Liseola in Argentina.     

Production of neosolaniol monoacetate by an undescribedFusarium species resemblingF camptoceras

Cultures of 12 South African isolates of an undescribedFusarium species resembling but distinct fromF camptoceras were analysed for the presence of diacetoxyscirpenol (DAS), neosolaniol monoacetate (NMA), and T-2 toxin, by capillary gas chromatography utilizing electron capture detection. No DAS or T-2 toxin could be detected in any of the cultures of the isolates. NMA was, however, detected in 10 of the 12 isolates at levels ranging from 310 to 2060 ng/g. The method used, was primarily developed for the determination of DAS and T-2 toxin in fungal cultures and grain samples but was found to be suitable for the coextraction of NMA at an average recovery of 80.8%, with a detection limit in the order of 100 ng/g. Supportive evidence for the presence of the NMA was obtained by capillary gas chromatography / mass spectrometry. Regarded as a relatively rare trichothecene, NMA has never been reported to occur naturally and has previously been shown to be produced by only a fewFusarium strains.     

Prevalence of Fusarium species of the Liseola section on selected Colombian animal feedstuffs and their ability to produce fumonisins

A total of 57 samples of feedstuffs commonly used for animal nutrition in Colombia (corn, soybean, sorghum, cottonseed meal, sunflower seed meal, wheat middlings and rice) were analyzed for Fusarium contamination. Fusarium fungi were identified at species level by means of conventional methods and the ability to produce fumonisins of the most prevailing species was determined. A total of 41 of the feedstuffs analyzed (71.9%) were found to contain Fusarium spp. Most contaminated substrates were corn (100%), cottonseed meal (100%), sorghum (80%), and soybean (80%). Wheat middlings and rice showed lower levels of contamination (40% and 20%, respectively), while no Fusarium spp. could be isolated from sunflower seed meal. The most prevalent species of Fusarium isolated were F. verticilliodes (70.8%), F.␣proliferatum (25.0%), and F. subglutinans (4.2%). All of them correspond to section Liseola.Production of fumonisins on corn by the isolated Fusarium was screened through liquid chromatography. Almost all strains of F. verticilliodes (97.1%) produced FB1 (5.6–25,846.4 mg/kg) and FB2 (3.4–7507.5 mg/kg). Similarly, almost all strains of F.␣proliferatum (91.7%) produced fumonisins but at lower levels than F.␣verticilliodes (FB1 from 6.9 to 3885.0 mg/kg, and FB2 from 34.3 to 373.8 mg/kg), while F. subglutinans did not produce these toxins. This is the first study in Colombia describing toxigenic Fusarium isolates from␣animal feedstuffs.     

Production of Beauvericin, Moniliformin, Fusaproliferin, and Fumonisins B1, B2, and B3 by Fifteen Ex-Type Strains of Fusarium Species

Fifteen Fusarium species were analyzed by high-performance liquid chromatography for the production of six mycotoxins in corn grits cultures. Production of mycotoxins ranged from 66 to 2,500 μg/kg for fumonisin B₁, 0.6 to 1,500 μg/g for moniliformin, 2.2 to 720 μg/g for beauvericin, and 12 to 130 μg/g for fusaproliferin. Fumonisin B₂ (360 μg/kg) was produced by two species, fumonisin B₃ was not detected in any of the 15 species examined, and Fusarium bulbicola produced none of the six mycotoxins that we analyzed.     

Effects of Management Practices on Nematode and Fungi Populations and Okra Yield

Okra was grown in field plots of Tifton loamy sand naturally infested with the nematodes Meloidogyne incognita and Criconemoides ornalus and the pathogenic fungi Fusarium oxysporum, F. solani, F. roseum, and Pythium spp. Plots were treated with various soil pesticides and left exposed or covered with biodegradable paper film mulch under trickle irrigation. Soil was assayed for nematodes and fungi, and plant roots were examined for root-rot and insect damage. Fewer nematodes and fungi generally were recovered from soil treated with DD-MENCS (with and without film mulch) or methyl bromide-chloropicrin (2:1) (MBC) and film mulch than from nontreated soil. Funfigation with DD-MENCS or MBC suppressed populations of M. incognita, C. ornatus, F. oxysporum, F. solani, F. roseum, and Pythium spp. Ethoprop (alone or combined with other pesticides), sodium azide, and chloroneb were less effective than DD-MENCS and MBC. Plant growth anti yield were greatest when nematodes and pathogenic fungi were controlled. Yield was increased 3-fold by DD-MENCS + film mulch or MBC + film mulch in comparison with the average yield of okra produced in Georgia. The root-knot nematode-Fusarium wilt complex was most severe in nonfuntigated soil.     

Biological Control of Fusarium spp. in Cotton, Wheat and Muskmelon by Trichoderma harzianum

A new isolate of Trichoderma harzianum (T-35) was isolated from the rhizosphere of cotton plants from a field infested with Fusarium. Under glasshouse conditions, the antagonist was applied to soil growing in a bran/peat mixture (1:1, v/v) or as a conidial suspension or used as a seed coating. When T. harzianum was tested against Fusarium oxysporum f. sp. vasinfectum, F. oxysporum f. sp. melonis or F. roseum‘Culmorum”, a significant disease reduction, was obtained in cotton, melon and wheat, respectively. Biological control of Fusarium wilt of cotton was achieved when tested at two inoculum levels of the pathogen (2 × 10⁷ and 2 × 10⁸ microconidia/kg soil), decreasing the Fusarium spp. soil population. The long term effect of T. harzianum on Fusarium wilt of cotton was studied using successive plantings. The antagonist persisted in soil throughout three consecutive plantings, reducing the Fusarium, wilt incidence in each growth cycle. At the first planting the largest amount of preparation was found superior, whereas at the third planting, no significant difference could be observed between the four rates of Trichoderma preparation. T. harzianum (T-35) controlled Fusarium wilt in cotton and muskmelon when applied in both naturally or artificially infested alluvial vertisol and sandy-loam soils, respectively. Soil or seed treatments with the antagonist provided a similar disease control of F. roseum‘Culmorum’ and of F. oxysporum f. sp. melonis.     

Occurrence of Trichothecin in Wheat

Trichothecin, a toxic metabolite of Trichothecium roseum, was detected in 3 of 13 wheat samples examined at levels of 560, 290, and 270 ng/g. In addition, all the T. roseum isolates from the wheat produced the toxin on wheat.     

Beauvericin Production by Fusarium Species

Beauvericin is a cyclohexadepsipeptide mycotoxin which has insecticidal properties and which can induce apoptosis in mammalian cells. Beauvericin is produced by some entomo- and phytopathogenic Fusarium species (Fusarium proliferatum, F. semitectum, and F. subglutinans) and occurs naturally on corn and corn-based foods and feeds infected by Fusarium spp. We tested 94 Fusarium isolates belonging to 25 taxa, 21 in 6 of the 12 sections of the Fusarium genus and 4 that have been described recently, for the ability to produce beauvericin. Beauvericin was produced by the following species (with the number of toxigenic strains compared with the number of tested strains given in parentheses): Fusarium acuminatum var. acuminatum (1 of 4), Fusarium acuminatum var. armeniacum (1 of 3), F. anthophilum (1 of 2), F. avenaceum (1 of 6), F. beomiforme (1 of 1), F. dlamini (2 of 2), F. equiseti (2 of 3), F. longipes (1 of 2), F. nygamai (2 of 2), F. oxysporum (4 of 7), F. poae (4 of 4), F. sambucinum (12 of 14), and F. subglutinans (3 of 3). These results indicate that beauvericin is produced by many species in the genus Fusarium and that it may be a contaminant of cereals other than maize.     

Role of Zearalenone Lactonase in Protection of Gliocladium roseum from Fungitoxic Effects of the Mycotoxin Zearalenone

Zearalenone is a mycotoxin with estrogenic effects on mammals that is produced by several species of Fusarium. We found that zearalenone and its derivatives inhibit the growth of filamentous fungi on solid media at concentrations of ≤10 μg/ml. The fungitoxic effect declined in the order zearalenone > α-zearalenol > β-zearalenol. The mycoparasitic fungus Gliocladium roseum produces a zearalenone-specific lactonase which catalyzes the hydrolysis of zearalenone, followed by a spontaneous decarboxylation. The growth of G. roseum was not inhibited by zearalenone, and the lactonase may protect G. roseum from the toxic effects of this mycotoxin. We inactivated zes2, the gene encoding zearalenone lactonase in G. roseum, by inserting a hygromycin resistance cassette into the coding sequence of the gene by means of Agrobacterium tumefaciens-mediated genetic transformation. The zes2 disruption mutants could not hydrolyze the lactone bond of zearalenone and were more sensitive to zearalenone. These data are consistent with a hypothesis that resorcylic acid lactones exemplified by zearalenone act to reduce growth competition by preventing competing fungi from colonizing substrates occupied by zearalenone producers and suggest that they may play a role in fungal defense against mycoparasites.     

Incidence of Fusarium spp. and Levels of Fumonisin B1 in Maize in Western Kenya

Maize kernel samples were collected in 1996 from smallholder farm storages in the districts of Bomet, Bungoma, Kakamega, Kericho, Kisii, Nandi, Siaya, Trans Nzoia, and Vihiga in the tropical highlands of western Kenya. Two-thirds of the samples were good-quality maize, and one-third were poor-quality maize with a high incidence of visibly diseased kernels. One hundred fifty-three maize samples were assessed for Fusarium infection by culturing kernels on a selective medium. The isolates obtained were identified to the species level based on morphology and on formation of the sexual stage in Gibberella fujikuroi mating population tests. Fusarium moniliforme (G. fujikuroi mating population A) was isolated most frequently, but F. subglutinans (G. fujikuroi mating population E), F. graminearum, F. oxysporum, F. solani, and other Fusarium species were also isolated. The high incidence of kernel infection with the fumonisin-producing species F. moniliforme indicated a potential for fumonisin contamination of Kenyan maize. However, analysis of 197 maize kernel samples by high-performance liquid chromatography found little fumonisin B₁ in most of the samples. Forty-seven percent of the samples contained fumonisin B₁ at levels above the detection limit (100 ng/g), but only 5% were above 1,000 ng/g, a proposed level of concern for human consumption. The four most-contaminated samples, with fumonisin B₁ levels ranging from 3,600 to 11,600 ng/g, were from poor-quality maize collected in the Kisii district. Many samples with a high incidence of visibly diseased kernels contained little or no fumonisin B₁, despite the presence of F. moniliforme. This result may be attributable to the inability of F. moniliforme isolates present in Kenyan maize to produce fumonisins, to the presence of other ear rot fungi, and/or to environmental conditions unfavorable for fumonisin production.     

Moniliformin and the European Corn Borer (<Emphasis Type="Italic">Ostrinia nubilalis</Emphasis>)

A representative survey was made of maize ears of the 1988 and 1989 crop in Austria to establish the influence of corn borer injuries onFusarium species involved in ear fusariosis andFusarium toxin production.TheFusarium species most frequently isolated from rot-damaged ears wereFsacchari var. subglutinans (about 50 %) andF. graminearum (about 30 %). There was a striking difference between theFusarium species of the Liseola and the Discolor section concerning their occurrence on corn borer-damaged ears. More than 80 % of the ears infected withF. sacchari var. subglutinans andF. verticillioides, but less than 15 % of the ears infected withF. graminearum, F. crookwellense andF. culmorum showed corn borer injuries.Toxin analyses of the infected ears corresponded to the known toxigenicity of the respectiveFusarium species. Ears infected withF. sacchari var. subglutinans contained moniliformin (up to 20 mg/kg), those infected withF. verticillioides fumonisin B₁ and B₂ (up to 15 mg/kg). In ears infected withF. graminearum, F. culmorum andF. crookwellense zearalenone (up to 40 mg/kg) and deoxynivalenol (up to 500 mg/kg) or nivalenol (up to 10 mg/kg), respectively, could be detected. Hence measures to combat the European corn borer will mainly reduce moniliformin and fumonisin contamination, but will affect zearalenone, deoxynivalenol and nivalenol contents of the ears to a much lesser extent.     

Natural occurrence of Fusarium species and fumonisin-production by toxigenic strains isolated from poultry feeds in Argentina

Fusarium species and fumonisin production by toxigenic strains were investigated. During 1996–1998, 158 samples of poultry feeds were collected from a factory located in the department of Río Cuarto Córdoba province, Argentina. The most common species of Fusarium were F. moniliforme (60.7%) and F. nygamai (35.4%) followed by F. semitectum, F. subglutinans, F. proliferatum, F. dlamini, F. solani, F. oxysporum and F. napiforme. Fungal counts ranged from 1 × 10³ to 8 × 10⁵ CFU/g with mean values from 1.5 × 10³ to 2.3 × 10⁵ CFU/g. The highest counts were for F. dlamini, F. subglutinans, F. moniliforme and F. nygamai. Strains of F. moniliforme, F. nygamai, and F. proliferatum were screened for their potential to produce fumonisin B₁ (FB₁), fumonisin B₂ (FB₂) and fumonisin B₃ (FB₃) in corn grain. The samples were analysed using a modified high performance liquid chromatography method. The strains assayed, 43 strains, produced three fumonisins. There was a high degree of variability in the quantities of FB₁, FB₂, and FB₃ produced. The toxin produced in highest levels by the majority of the strains was FB₁. The range of concentration varied from 5.4 to 3,991, 1.01 to 189 and 0.4 to 765 ppm per gram of corn for FB₁, FB₂ and FB₃ respectively. The toxigenic pattern of strains was normal, although two strains of F. moniliforme produced exceptionally high concentrations of FB₃ and minor concentrations of FB₂ and FB₁. This is the first report from Argentina on Fusarium species in poultry feeds and fumonisin production by these strains.This revised version was published online in October 2005 with corrections to the Cover Date.     

Microbiological Production of Gibberellic Acid in Glucose Media

Gibberellic acid production from various substrates was studied in 43 strains of Fusarium, among which F. moniliforme strain IOC-3326 was selected as the best producer. Experiments were carried out in shaker flasks and pilot plant fermentors. The results indicate that the best substrate for gibberellic acid production with this strain is composed of the following: glucose, 20 g; corn steep liquor, 25 g; ammonium nitrate, 2.6 g; monopotassium phosphate, 0.5 g; potassium sulfate, 0.2 g; and water, 1000 ml. Glucose, ammonium nitrate, and corn steep liquor were found to be critical. With this medium, maximal yields of 1196 mg per liter in shaker flasks and 997 mg per liter in fermentors were produced.     

Occurrence of fumonisins in asparagus (asparagus officinalis L.) and garlic (allium sativum L.) from Germany

Fusarium proliferatum is able to produce fumonisins and is considered a pathogen of many economically important plants (e.g. corn, rice, asparagus) [1]. The occurrence of fumonisin FB₁ inF. proliferatum infected asparagus spears from Germany was investigated using a liquid chromatography/electrospray ionization-mass spectrometry (LC-ESI-MS) method with isotopically labeled fumonisin FB₁-d₆ as internal standard. Asparagus samples were harvested in July 2000 and screened forFusarium species. AltogetherF. oxysporum, F. proliferatum and F. sambucinum were isolated from the spears. The samples infected with F.proliferatum were subsequently analyzed for fumonisins. FB₁ was detected in 9 of the 10 samples in amounts ranging from 36.4 ng/g to 4513.7 ng/g (based on dry weight). Fumonisins FB₂ and FB₃ were found in six samples in lower concentrations. In asparagus spears of June 2002 we could findF. proliferatum in 6% of the samples, however no fumonisins were detectable. Furthermore the capability of producing FB₁ by the fungus in garlic bulbs was investigated. Therefore garlic was cultured inF. proliferatum contaminated soil and the bulbs were screened for infection with F.proliferatum and for the occurrence of fumonisins by LC-MS. F.proliferatum was detectable in the garlic tissue and all samples contained FB₁ (26.0 ng/g to 94.6 ng/g). This is the first report of the natural occurrence of FB₁ in German asparagus spears and furthermore our findings suggest a potential for natural contamination of garlic bulbs with fumonisins. For detailed results and methods see Ref. [2].     

Fusarium poae and Fusarium crookwellense, Fungi Responsible for the Natural Occurrence of Nivalenol in Hokkaido

To determine the reasons for the natural occurrence of nivalenol in the northernmost area of Japan, scabby wheat was harvested from 19 crop fields in Hokkaido. Mycological surveys and analysis for mycotoxin contamination were performed. Among 13 wheat grain samples harvested in seven locations, 9, 2, and 6 samples were positive for deoxynivalenol, nivalenol, and zearalenone, respectively, at levels ranging from 0.03 to 1.28 μg/g, 0.04 to 1.22 μg/g, and 2 to 25 ng/g, respectively. The predominant Fusarium species of the scabby wheat examined were F. sporotrichioides, F. avenaceum, F. poae, and F. crookwellense. Fifteen of 48 F. poae isolates and all four F. crookwellense isolates were screened for the production of seven derivatives of trichothecenes and zearalenone respectively, on rice culture. One isolate of F. poae produced diacetoxyscirpenol alone (4.3 μg/g); seven produced nivalenol (1.3 to 23.8 μg/g), 4-acetylnivalenol (0.1 to 4.6 μg/g), and diacetoxyscirpenol (0.9 to 99.5 μg/g); and five produced nivalenol alone (0.4 to 3.5 μg/g). The remaining two isolates produced no trichothecenes. Zearalenone production was not found in any isolate of F. poae tested. All isolates of F. crookwellense produced nivalenol (0.9 to 22.5 μg/g), 4-acetylnivalenol (0.5 to 25.0 μg/g), and zearalenone (1.4 to 162.5 μg/g). From these results, it is apparent that deoxynivalenol and zearalenone, and occasionally nivalenol, occur naturally throughout Hokkaido, and it is suggested that nivalenol-producing F. poae and F. crookwellense strains are responsible for the natural contamination with nivalenol found in the northernmost area of Japan. Furthermore, it was found for the first time that several isolates of F. poae distributed in Hokkaido possessed the ability to produce both type A and type B trichothecenes.     

Screening fusarium strains isolated from overwintered Canadian grains for trichothecenes

A survey of 38 samples of Canadian overwintered grains showed that 14 (37 %) contained viableFusarium. Of a total of 38Fusarium isolates, cultured on autoclaved corn, 20 (from 7 grain samples) showed toxicity to brine shrimp larvae and 12 (from 5 samples) produced levels of trichothecenes detectable by thin layer chromatography. The principal trichothecene found was T-2 toxin, produced by 10 strains and accompanied in half of these by neosolaniol; some of these strains were identified asF. sporotrichioides Sherbakoff. Two strains ofF. poae (Peck) Wollenw. formed small amounts of diacetoxyscirpenol. T-2 toxin was the most toxic of 8 trichothecenes tested on brine shrimp larvae; the wide range of toxicities limits the usefulness of this bioassay as a general screening method for trichothecenes.     

Survey for Fusaria that produce and antibiotic that causes conidia of Penicillium digitatum to swell

During screening of Fusarium Lk. ex Fr. strains for antibiotic production, we observed a peculiar conidial swelling of Penicillium digitatum Sacc. strain NRRL 1202 when this sensitive fungus was grown in the presence of methanol extracts of Fusarium roseum Lk. Acuminatum strain NRRL 6227 cultures. In an expanded study to determine the prevalence of a swelling factor among Fusarium species, 23 of 132 strains produced an antibiotic that caused P. digitatum conidia to swell. Eighteen of the producing fungi belonged to the species F. tricinctum (Cda.) Sacc, two were identified as F. roseum Acuminatum, and one strain each was identified as F. roseum Sambucinum, F. roseum Equiseti and F. graminearum Schwabe. These data indicate that production of an antibiotic that causes P. digitatum conidia to swell is not unique to only a few Fusarium cultures.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Occurrence of Fusaproliferin and Beauvericin in Fusarium-Contaminated Livestock Feed in Iowa

Fusarium fungal contaminants and related mycotoxins were investigated in eight maize feed samples submitted to the Iowa State University Veterinary Diagnostic Laboratory. Fusarium moniliforme, F. proliferatum, and F. subglutinans were isolated from seven, eight, and five samples, respectively. These strains belonged to mating populations A, D, and E of the teleomorph Gibberella fujikuroi. Fusaproliferin was detected at concentrations of 0.1 to 30 μg/g in four samples, and beauvericin was detected (0.1 to 3.0 μg/g) in five samples. Fumonisins were detected in all eight samples (1.1 to 14 μg/g). Ten of 11 strains of F. proliferatum and all 12 strains of F. subglutinans isolated from the samples produced fusaproliferin in culture on whole maize kernels (4 to 350 and 100 to 1,000 μg/g, respectively). Nine F. proliferatum strains also produced beauvericin in culture (85 to 350 μg/g), but none of the F. subglutinans strains produced beauvericin. Fumonisin B₁ was produced by all nine F. moniliforme strains (50 to 2,000 μg/g) and by 10 of the F. proliferatum strains (1,000 to 2,000 μg/g). This is the first report of the natural occurrence of fusaproliferin outside Italy and of the natural occurrence of beauvericin in North America.