15-Acetoxyscirpenol

Epidemics of Fusarium head blight (FHB) occurred on barley in Minnesota, North Dakota, and South Dakota from 1993 to 1998. The Red River Valley region was most severely impacted by the disease based on assessments of FHB severity in grain samples harvested from commercial fields. Fusarium graminearum was the primary pathogen causing these FHB epidemics. It comprised from 62 to 64% of all Fusarium species isolated from infected kernels from 1994 to 1996. Fusarium poae (range of isolation 13 to 20%),F. sporotrichioides (10 to 17%), and F. avenaceum (6 to 10%) also were isolated from barley kernels and were likely involved in causing some FHB infection, but to a very limited extent. All four Fusarium species were pathogenic on barley in inoculation tests conducted in both the greenhouse and the field. Mycotoxin screens were performed on barley spikes inoculated with the respective species in the greenhouse. Spikes infected with F. graminearum contained deoxynivalenol and 15-acetyldeoxyni-valenol; those infected with F. sporotrichioides contained T-2 toxin, HT-2 toxin, and T-2 tetraol; and those infected with F. poae contained nivalenol. Some isolates of F. poae also produced 15-acetoxyscirpenol and scirpentriol. Although F. graminearum and DON are recognized as the primary FHB pathogen and mycotoxin, respectively, in barley, the possible presence of other Fusarium species and mycotoxins should not be overlooked.

Using the paper-disk method with Chlorella-seeded agar plates, 15-acetoxyscirpenol, HT-2 toxin, acetyl T-2 toxin and neosolaniol inhibited growth at a concentration of 1 mg/ml, whereas verrucarol, T-2 tetraol, nivalenol, fusarenon-X, deoxynivalenol and 3-acetyldeoxynivalenol were inactive. Taking into account that verrucarin A, roridin A, T-2 toxin and diacetoxyscirpenol had previously been found to strongly inhibit Chlorella growth, esterification at R15 appears to be important for growth inhibitory activity. The most active agents are also esterified at R4. Inhibition of protein synthesis appears to be involved in the toxicity.

An enzyme-linked immunosorbent assay (ELISA) for the detection of diacetoxyscirpenol (DAS) was developed. Antibodies against DAS were obtained after immunization of rabbits with DAS-hemiglutarate-human serum albumin (DAS-HG-HSA). After an immunization period of 6 weeks a sufficient level of specific antibodies was reached. A DAS-hemisuccinate-horseradish peroxidase-conjugate (DAS-HS-HRP) was prepared by an ester method and used as enzyme-labelled toxin in the competitive assay. The detection limit for DAS was about 10 pg/ml. The relative cross reactivity of the assay was 597.5, 5.2, 100.0, 2.5, and 1.5% for 3 alpha-acetyl-DAS, DAS, T-2 toxin, neosolaniol, and 15-acetoxyscirpenol, respectively.