Deoxynivalenol, acetyl deoxynivalenol, and zearalenone formation by Canadian isolates of Fusarium graminearum on solid substrates

Production of deoxynivalenol and zearalenone by isolates of Fusarium graminearum Schw

The production of deoxynivalenol (DONI) on rice, corn, wheat, and barley grains by Fusarium graminearum Schw. NRRL 5883 was investigated. Highest yields (91.9-202 ppm) were obtained on rice; yields on the other substrates were: corn (34.1-84.5 ppm), wheat (3.6-24.4 ppm), and barley (0-6.6 ppm). Fifty isolates of Fusarium from corn inoculated in the field in 1979 with a mixture of strains of F. graminearum, originally collected from corn plants infected with stalk rot, were tested for DONI production on corn. Twenty of these were also tested for zearalenone production. One isolate produced more than 200 ppm DONI, 13 produced 20-50 ppm, 17 produced 10-20 ppm, and the rest produced less than 10 ppm. The only isolate that did not produce DONI was not identified as F. graminearum. All 20 isolates tested produced zearalenone; 18 produced higher levels of zearalenone (15.4-369 ppm) than of DONI. The other 2 isolates formed essentially the same levels of zearalenone and DONI-37 and 30 ppm, and 15 and 16 ppm, respectively.

Toxigenic Potential of Some Fusarium Isolates from Southeast Asia

The isolation and characterization of 10 isolates of six Fusarium spp. from plant and soil samples collected in Southeast Asia is reported. The ability of these isolates to produce trichothecenes both in liquid cultures (CZ, GYEP, and MYRO) and on rice was assessed, and their toxigenic potential was examined by skin assay and gavage studies with culture filtrates. Although culture filtrates of all the isolates caused minor damage to test animals, only that of F. equiseti DAOM 189762 produced trichothecenes.

Deoxynivalenol and 15-monoacetyl deoxynivalenol production by Fusarium graminearum R6576 in liquid media

Growth and toxigenesis by Fusarium graminearum R6576, were compared in four liquid media. Parameters monitored during the fermentation were deoxynivalenol (DON) and 15-acetyl deoxynivalenol (15-ADON) production, fungal mass, carbohydrate utilization, and pH. Factors which were varied included basal medium composition, corn steep liquor (CSL) concentration, sucrose concentration and ammonium tartrate concentration. Growth in modified Fries medium resulted in only low levels of DON (0.25 mg/L) and 15-ADON (0.25 mg/L) after 20 days. Addition of 4% CSL to modified Fries medium raised the 20 day DON yield to 16.5 mg/l. Increasing the sucrose concentration in modified Fries medium amended with 4% CSL resulted in increased mycelial dry weight but decreased levels of DON. Concentrations of ammonium tartrate greater than 1% in modified Fries amended with 4% CSL greatly reduced DON yield. Use of glucose-yeast extract-peptone (GYEP) for toxin production resulted in higher yields of 15-ADON (14.0 mg/L) than DON (5.5 mg/L) after 20 days. However, supplementation of GYEP with 4% CSL resulted primarily in DON production (4.5 mg/L) after 20 days. In general, qualitative and quantitative production of DON and 15-ADON by Fusarium graminearum R6576 were dependent on the composition of the complex liquid medium.

Effect of Cultural Practices, Soil Phosphorus, Potassium, and pH on the Incidence of Fusarium Head Blight and Deoxynivalenol Levels in Wheat

In a survey conducted in 1984 in Essex, Lambton, and Middlesex Counties of Ontario, Canada, greater incidences of head blight and greater concentrations of deoxynivalenol in grain were observed in fields of winter wheat planted after corn than in those planted after soybeans, barley, and mixed grains. Neither head blight nor deoxynivalenol level were correlated significantly with soil P, K, or pH. Head blight was reduced in wheat planted after corn where the residues from a preceding corn crop were plowed down or where seed was treated with Vitaflo 280. However, head blight and deoxynivalenol levels were not affected significantly by the level of N application, cultivar, other diseases or herbicides.

Rejection by pigs of mouldy grain containing deoxynivalenol

Weaner pigs on a farm near Beaudesert in south eastern Queensland refused to eat feed comprised largely of wheat and barley. Older pigs consumed small amounts and some prepubertal gilts subsequently displayed enlarged and reddened vulvas. Wheat, barley and triticale were grown on the farm during 1983, which was unusually and persistently wet. The wheat and triticale were harvested and stored for about 3 weeks with moisture contents above 14% before being fed. Samples of the wheat and triticale contained pale pink grains, which can indicate infection by the fungus Fusarium graminearum Schw. On analysis 2 mycotoxins known to be produced by F. graminearum were detected, deoxynivalenol (vomitoxin) which causes feed refusal and vomiting, and zearalenone which causes oestrogenic effects. Concentrations of deoxynivalenol in the wheat, triticale and barley were 34, 10, and less than 0.1 mg/kg respectively. Concentrations of zearalenone were 6.2, 2.8 and 0.1 mg/kg respectively. Subsequently, F. graminearum was isolated from grains and crop residues. Although the wet weather contributed to F. graminearum infection of the crops before harvest, most of the toxins probably developed during storage.