Abstract:
Wheat seeds produced in 1987 and stored under
various conditions at research stations, seed farms, state
farms and farmer fields in different regions of Ethiopia were
checked for Fusarium infection. Fusarium was detected in 35 to
65% of the samples. Fusarium Head Blight (FHB) survey in wheat
fields in 1988 indicated as many as 85% of the plants in some
state farms showed head scab. Lower levels of FHB were
recorded at farmer fields. The results indicated that FHB can
be a major problem to wheat production in Ethiopia and a
breeding' program against the disease should be initiated.
Seventeen and thirteen Fusarium species were
identified from stored seed and scabby wheat heads in the
field, respectively. F. nivale and F. avenaceum were dominant
species in samples collected from cool, moist, high altitude
areas. F. graminearum was more frequent at lower altitude and
in northwestern regions. In both state farms and farmer
fields, F. soorotrichioides and F. poae occurred less frequently and had more limited distribution than F.
crraminearum. F. equiseti was more commonly isolated from
stored seed samples.
The majority of the Fusarium species did not produce
detectable amounts of either trichothecenes or zearalenone.
Two isolates of F. araminearum produced low levels of 3-
acetyldeoxynivalenol, 15-acetyldeoxynivalenol and zearalenone.
An isolate of F. poae produced a low level of neosolaniol.
A single strain, F. sporotrichioides #48d produced
a variety of trichothecenes. They were tentatively identified
by thin layer chromatography and gas chromatography-mass
spectrometry as neosolaniol, 8-acetylneosolaniol, 8-
p r o p i o n y l n e o s o l a n i o l , 8 -n-valerylneosolaniol , 8-
isovalerylneosolaniol (T-2 toxin), 8-n-butyrylneosolaniol, 8-
isobutyrylneosolaniol, 8-hexynylneosolaniol and 4,8-diacetyl
T-2 tetraol (NT-1). The 8-n-valerylneosolaniol and 8-
hexynylneosolaniol are reported for the first time.
Sensitivity of wheat cultivars to Fusarium toxins in
coleoptile elongation assay did not, generally, correlate with
their reaction to FHB in the field. The cultivars did not
respond similarly to all the mycotoxins or to different
concentrations of a single mycotoxin. Line HAR424, however,
exhibited low sensitivity to all mycotoxins as well as low FHB
in the field.
