Mycotoxin Production Potential of Fusarium Species Identified from Ethiopian Wheat.

Mycotoxins are seconday metabolites produced by fungi that are toxic to animals and hymans. They have been implicated in a number of human and animal disease syndromes (Mycotoxicoses). FAO has estimated that 25 percent of the world food crops and up to 50 percent of the crops in Africa are contaminated by mycotoxins. Many Fusarium species, apart from being pathogenic to cereal crops (eg. Fusarium Head Blight of wheat), produce various mycotoxins. A good example of Fusarium mycotoxicoses in human is Alimentary Toxic Aleukia (ATA) which was wide spread among the population of the Soviet Union during World War II. Two groups of mycotoxins: zearalenone and trichothecenes (and their derivatives) are produced by many toxigenic Fusarium strains. Seventy-eight isolates from 17 Fusarium species isolated from stored wheat seed and scabby heads were screened for mycotoxin production on solid and liquid media. The presence of the mycotoxins in culture filtrate was detected by thin-layer chroma-tography (TLC) and confirmed by gas chromatography-mass spectroscopy (GC-MS). Most of the isolates did not produce a detectable amount of any of the mycotoxins in potato dextrose broth (PDB) liquid medium. However, a few species and isolates produced some of the mycotoxins on corn grit and rice solid media. Two Fusarium graminearum isolates produced low levels of 3=acetyldexynivalenol (3-ADON) and 15-acetyldeoxynivalenol (15-ADON). Both these isolates produced low level zearalenone. An isolate of F. sporotricioides which was a rare species isolated from Ethiopian wheat, however, produced a variety of trichothecenes on corn grits. The trichothecenes were neosolaniol, NT-1, 8-Acetylneosolaniol, 8-Propionylneosolaniol, 8-Isobutrylneoxolaniol, 8-n-Butrylneosolaniol, T-2 toxin, 8-n-Pentanoylneosolaniol and 8-n-Hexanoylneosolaniol. The last two trichothecenes are reported for the first time. The cytotoxicity of these two new trichothecenes in cultured body hamster kidney cells was comparable to that of T-2 toxin. Unlike most European and North American isolates, this isolate produced T-2 toxin as a minor product and neosolaniol as well as a number of C-8 substituted derivatives as major metabolites. F. nivale and F. avenaceum which were commonly isolated from scabby wheat heads in Ethiopia did not produce any of the mycotoxins under the different culturing conditions used or if present could not be detected with the procedures employed. The result indicated that although Fusarium head blight was a major problem to the wheat crop, the major species that caused the disease were not toxigenic to animals and humans.