Variability in the production of trichothecenes by Fusarium sporotrichioides

Production of trichothecenes as with all secondary metabolites, will vary from one producing strain to another. If a particular metabolite is produced at all it may be assumed that the part of the genome involved is intact and it would seem most likely that the quantitative variation observed from strain to strain might arise from modifications in metabolic control. An opportunity to study this phenomenon is presented by the existence of cultures of Fusarium sporotrichioides descended from the original T-2 toxin producing strain isolated in 1965 from French corn by W.C. Snyder and originally referred to as F. tricinctum and since then maintained independently by different culture collections. These strains continue to be T-2 toxin producers but are now morphologically distinct on media such as potato sucrose agar.Preliminary results are reported in studies designed to detail the differences in toxigenicity between these strains.     

New modified trichothecenes accumulated in solid culture by mutant strains of Fusarium sporotrichioides.

Mutant strains of Fusarium sporotrichioides NRRL 3299 deficient in the ability to synthesize T-2 toxin were examined on solid rice medium. Five novel alicyclic trichothecenes were isolated: 11 alpha-hydroxytrichodiene; tricho-9-ene-2 alpha,3 alpha,11 alpha-triol; tricho-9-ene-2 alpha,3 alpha,8 alpha,11 alpha-tetraol; tricho-9-ene-2 alpha,3 alpha,8 beta,11 alpha-tetraol; and tricho-9-ene-2 alpha,3 alpha,11 alpha,16-tetraol.     

Isolation and characterization of two new trichothecenes from Fusarium sporotrichioides strain M-1-1.

Two new trichothecenes were isolated along with T-2 toxin, neosolaniol, and HT-2 toxin from the culture filtrate of Fusarium sporotrichioides strain M-1-1. The structures of the new toxins were characterized to be 4 beta, 8 alpha-diacetoxy-12,13-epoxytrichothec-9-ene-3 alpha, 15-diol (designated NT-1) and 4 beta-acetoxy-12,13-epoxy-trichothec-9-ene-3 alpha,8 alpha,15-triol (designated NT-2).     

New modified trichothecenes accumulated in solid culture by mutant strains of Fusarium sporotrichioides

Mutant strains of Fusarium sporotrichioides NRRL 3299 deficient in the ability to synthesize T-2 toxin were examined on solid rice medium. Five novel alicyclic trichothecenes were isolated: 11 alpha-hydroxytrichodiene; tricho-9-ene-2 alpha,3 alpha,11 alpha-triol; tricho-9-ene-2 alpha,3 alpha,8 alpha,11 alpha-tetraol; tricho-9-ene-2 alpha,3 alpha,8 beta,11 alpha-tetraol; and tricho-9-ene-2 alpha,3 alpha,11 alpha,16-tetraol.     

Comparative yields of T-2 toxin and related trichothecenes from five toxicologically important strains of Fusarium sporotrichioides.

The range and comparative yields of T-2 toxin and related trichothecenes from five toxicologically important strains of Fusarium sporotrichioides, i.e., NRRL 3299, NRRL 3510, M-1-1, HPB 071178-13, and F-38, were determined. Lyophilized cultures of the five strains maintained in the International Toxic Fusarium Reference Collection were used to inoculate autoclaved corn kernels. Corn cultures were incubated at 15 degrees C for 21 days and analyzed for trichothecenes by thin-layer chromatography and capillary gas chromatography. All five strains produced T-2 toxin, HT-2 toxin, T-2 triol, and neosolaniol. Two strains also produced T-2 tetraol, and two others produced diacetoxyscirpenol. The highest producer of T-2 toxin (1,300 mg/kg), HT-2 toxin (200 mg/kg), T-2 triol (1.9 mg/kg), and neosolaniol (170 mg/kg) was NRRL 3510, which was originally isolated from millet associated with outbreaks of alimentary toxic aleukia in the USSR. The second highest producer of T-2 toxin (930 mg/kg) was NRRL 3299. The other three strains produced T-2 toxin at levels ranging from 130 to 660 mg/kg. Thus, the five strains differed considerably in the amounts of T-2 toxin and other trichothecenes produced under identical laboratory conditions. These strains are being maintained under optimal conditions for the preservation of Fusarium cultures and are available from the Fusarium Research Center, The Pennsylvania State University, University Park.     

Formation of moniliformin by Fusarium sporotrichioides and Fusarium culmorum.

Two strains of Fusarium sporotrichioides and one strain of F. culmorum were shown to produce the mycotoxin moniliformin in rice culture. Identification was by reverse-phase liquid chromatography, thin-layer chromatography, and mass spectrometry.     

Comparative yields of T-2 toxin and related trichothecenes from five toxicologically important strains of Fusarium sporotrichioides

The range and comparative yields of T-2 toxin and related trichothecenes from five toxicologically important strains of Fusarium sporotrichioides, i.e., NRRL 3299, NRRL 3510, M-1-1, HPB 071178-13, and F-38, were determined. Lyophilized cultures of the five strains maintained in the International Toxic Fusarium Reference Collection were used to inoculate autoclaved corn kernels. Corn cultures were incubated at 15 degrees C for 21 days and analyzed for trichothecenes by thin-layer chromatography and capillary gas chromatography. All five strains produced T-2 toxin, HT-2 toxin, T-2 triol, and neosolaniol. Two strains also produced T-2 tetraol, and two others produced diacetoxyscirpenol. The highest producer of T-2 toxin (1,300 mg/kg), HT-2 toxin (200 mg/kg), T-2 triol (1.9 mg/kg), and neosolaniol (170 mg/kg) was NRRL 3510, which was originally isolated from millet associated with outbreaks of alimentary toxic aleukia in the USSR. The second highest producer of T-2 toxin (930 mg/kg) was NRRL 3299. The other three strains produced T-2 toxin at levels ranging from 130 to 660 mg/kg. Thus, the five strains differed considerably in the amounts of T-2 toxin and other trichothecenes produced under identical laboratory conditions. These strains are being maintained under optimal conditions for the preservation of Fusarium cultures and are available from the Fusarium Research Center, The Pennsylvania State University, University Park.     

Heterokaryosis in Fusarium tricinctum and F. sporotrichioides

Heterokaryons were formed in intra- and interspecific crosses between Fusarium sporotrichioides and F. tricinctum auxotrophs. Segregant homokaryons were evaluated for trichothecene toxin production in culture. Results were consistent with nuclear control of toxin synthesis. The sexual compatibility of auxotrophs and 30 additional F. tricinctum sensu Snyder & Hansen strains was tested. Perithecial production was restricted to crosses between Florida isolates pathogenic to English ivy (Hedera helix). The linkage of several auxotrophic markers was determined by analysis of progeny of certain crosses. No T-2 toxin was produced by sexually compatible F. tricinctum isolates.     

Natural occurrence of Fusarium mycotoxins (trichothecenes and zearalenone) in barley and corn in Korea.

Barley is produced in four provinces, Chonbuk, Chonnam, Kyungbuk, and Kyungnam, and corn is mainly produced in the Kangwon province in Korea. The natural occurrence of Fusarium mycotoxins was surveyed in 39 barley and 46 corn samples from different areas. Five 8-ketotrichothecenes, namely deoxynivalenol (DON), nivalenol (NIV), 4-acetylnivalenol (4-ANIV), 3-acetyldeoxynivalenol (3-ADON), and 4,15-diacetylnivalenol (4,15-DANIV), and zearalenone (ZEA) were detected in barley. DON, NIV, and ZEA were the major contaminants in barley, with mean levels of 170, 1,011, and 287 ng/g, respectively. On the other hand, DON, 15-acetyldeoxynivalenol (15-ADON), NIV, 4-ANIV, 4,15-DANIV, and ZEA were detected in corn samples. DON and 15-ADON were the major contaminants in corn, with mean levels of 310 and 297 ng/g, respectively. The survey indicated that the natural occurrence of monoacetyl-DON and the ratios of NIV to DON in two cereals were different. In addition, this is the first report of the natural occurrence of 4,15-DANIV in cereals.     

Formation of moniliformin by Fusarium sporotrichioides and Fusarium culmorum

Two strains of Fusarium sporotrichioides and one strain of F. culmorum were shown to produce the mycotoxin moniliformin in rice culture. Identification was by reverse-phase liquid chromatography, thin-layer chromatography, and mass spectrometry.     

Acceptance by swine and rats of corn amended with trichothecenes.

Swine and rats demonstrated the same response factor (i.e., the average amount of corn amended with trichothecenes consumed by animals per the average amount of uncontaminated corn consumed by animals) for consumption of corn amended with 40 ppm of either T-2 toxin or diacetoxyscirpenol Rat response factor for corn containing 40 ppm of vomitoxin was 1.8 times more than corn containing either T-2 toxin or diacetoxyscirpenol at 40 ppm. For the corn containing 40 ppm of vomitoxin, swine response factor was 1.8 times greater than rat response factor.     

Mycotoxins and Fusarium spp. associated with infected ears of corn in Minnesota.

Five Fusarium species were isolated from the grain of dent corn (Zea mays) selected from 20 of 32 damaged fields in 10 counties in Minnesota on the basis of hyphal growth visible on kernels in the field. Three mycotoxins were identified in the infected ears: zearalenone, deoxynivalenol, and 15-acetyl-deoxynivalenol. This is the first report of the presence of 15-acetyl-deoxynivalenol on corn ears in the field prior to harvest and in combination with deoxynivalenol and zearalenone. Ninety-nine cultures were selected from colonies growing from kernels on an agar medium; 30% of the cultures were F. graminearum, 23% were F. subglutinans, 20% were F. moniliforme, 14% were F. oxysporum, and 12% were F. proliferatum.     

Mycotoxins and Fusarium spp. associated with infected ears of corn in Minnesota

Five Fusarium species were isolated from the grain of dent corn (Zea mays) selected from 20 of 32 damaged fields in 10 counties in Minnesota on the basis of hyphal growth visible on kernels in the field. Three mycotoxins were identified in the infected ears: zearalenone, deoxynivalenol, and 15-acetyl-deoxynivalenol. This is the first report of the presence of 15-acetyl-deoxynivalenol on corn ears in the field prior to harvest and in combination with deoxynivalenol and zearalenone. Ninety-nine cultures were selected from colonies growing from kernels on an agar medium; 30% of the cultures were F. graminearum, 23% were F. subglutinans, 20% were F. moniliforme, 14% were F. oxysporum, and 12% were F. proliferatum.     

Fusarium species associated with banana fruit rot and their potential toxigenicity

Banana fruits exhibiting signs of decay were collected from markets in the United States and Italy. Fungi isolated from the lesions on the banana fruits wereFusarium moniliforme, F subglutinans, andF. semitectum var.majus. When the fungal strains were cultivated on maize kernels, the cultures did not produce zearalenone (ZON), zearalenols (á-, â-ZOH), and trichothecenes [deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), T-2 toxin (T-2), diacetoxyscirpenol (DAS)]. Fumonisins and fusarin C (FUS-C) were not detected naturally nor in bananas purchased in the U.S. and artificially infected withFusarium. Moniliformin (M) (up to 267 mg/kg) was detected in maize kernel cultures ofF. subglutinans from bananas. No mycotoxins were detected in naturally infected fruits. Although no mycotoxins were detected in the extracts from corn cultures ofF. semitectum var.majus, the extracts were toxic to brine shrimp and mice.     

Mycotoxin production by Fusarium oxysporum and Fusarium sporotrichioides isolated from Baccharis spp. from Brazil.

Fusarium oxysporum isolated from roots of and soil around Baccharis species from Brazil produced the trichothecenes T-2 toxin, HT-2 toxin, diacetoxyscirpenol, and 3'-OH T-2 (TC-1), whereas Fusarium sporotrichioides from the same source produced T-2 toxin, HT-2 toxin, acetyl T-2, neosolaniol, TC-1, 3'-OH HT-2 (TC-3), iso-T-2, T-2 triol, T-2 tetraol, and the nontrichothecenes moniliformin and fusarin C. Several unknown toxins were found but not identified. Not found were macrocyclic trichothecenes, zearalenone, wortmannin, and fusarochromanone (TDP-1).     

Formation of trichothecenes by Fusarium solani var. coeruleum and Fusarium sambucinum in potatoes.

Fusarium solani var. coeruleum can form deoxynivalenol in potato tubers and in liquid medium, although concentrations observed in the rot were highly variable; acetyldeoxynivalenol and HT-2 toxin were detected in 1 to 3 tubers only (of 57). Trichothecenes were also detected in a very few (3 of 20) cultures of Fusarium sambucinum in potato tubers.     

Mycotoxin production by Fusarium oxysporum and Fusarium sporotrichioides isolated from Baccharis spp. from Brazil

Fusarium oxysporum isolated from roots of and soil around Baccharis species from Brazil produced the trichothecenes T-2 toxin, HT-2 toxin, diacetoxyscirpenol, and 3'-OH T-2 (TC-1), whereas Fusarium sporotrichioides from the same source produced T-2 toxin, HT-2 toxin, acetyl T-2, neosolaniol, TC-1, 3'-OH HT-2 (TC-3), iso-T-2, T-2 triol, T-2 tetraol, and the nontrichothecenes moniliformin and fusarin C. Several unknown toxins were found but not identified. Not found were macrocyclic trichothecenes, zearalenone, wortmannin, and fusarochromanone (TDP-1).     

Zearalenone, deoxynivalenol, and T-2 toxin associated with stalk rot in corn.

The mycotoxins zearalenone (2.8 micrograms/g), deoxynivalenol (1.5 microgram/g), and T-2 toxin (110 ng/g) have been found in the pith of corn stalks standing in the field. Such contaminated stalks may contribute to mycotoxicoses of farm animals.