New Zealand Journal of Crop and Horticultural Science abstracts
Fusaria and Fusarium mycotoxins in leaves and ears of maize plants 2.
A time course study made in the Waikato region, New Zealand, in 1997
D. R. LAUREN
The Horticulture and Food Research
Institute of New Zealand Ltd
Ruakura Research Centre
Private Bag 3123
Hamilton, New Zealand
email: dlauren@hort.cri.nz
M. E. DI MENNA
New Zealand Pastoral Agriculture
Research Institute Limited
Ruakura Research Centre
Private Bag 3123
Hamilton, New Zealand
Abstract The patterns of fungal infection and mycotoxin
contamination in leaf and ear sections of plants of two maize (
Zea mays
L.) hybrids, one resistant to mycotoxin accumulation under New Zealand
conditions (Pioneer 3902 (P3902)) and one less so (Pioneer 3751 (P3751)), have
been measured. Sampling commenced early in the season, well before ear and
tassel formation, and continued until harvest. A number of fungi were isolated,
the most common overall being
Fusarium. Most common in leaf fractions
were
Epicoccum,
Fusarium, and
Alternaria, whereas in ear
fractions the most common were
Fusarium,
Penicillium,
Cladosporium,
and
Mucor. The most common fusaria isolated
from leaf fractions were the toxigenic species
F. crookwellense and
F. graminearum. These species were evident from late February although
other, non-toxigenic, species were present in leaf axils from early January.
For ear fractions the most common species were
F. graminearum,
F.
crookwellense, and
F. subglutinans.
Fusarium infection was
evident in ears of P3902 from March to April, although heavy infection by the
toxigenic species tended to occur later towards May-June, especially for the
basal ear fractions. For P3751 ear infection commenced in May, and then was
predominantly by toxigenic species. Mycotoxins were found in most plant
fractions measured, especially as the plants aged. The toxins found reflected
the particular toxigenic
Fusarium species present in the fraction. The
highest mycotoxin concentration in a leaf fraction was 16.6 mg/kg of
zearalenone (ZEN) in an upper leaf axil sample. Nivalenol (NIV) was also found
at up to 7.4 mg/kg in leaf axils. The most contaminated ear fraction was the
rachis, with over 40-95 mg/kg of ZEN, NIV, or deoxynivalenol (DON) at various
times. The highest concentration found in kernels was 3.8 mg/kg of DON found in
apical kernels of P3751 two weeks before harvest. The results suggest that the
mechanisms of maize infection by
Fusarium in New Zealand may not be
controlled by factors at silk emergence but rather by later season events such
as high rainfall and warmer temperatures.
Keywords maize; mycotoxins; Fusarium; F.
graminearum; F. crookwellense; infection; plant fractions
H98061
Received 10 December 1998; accepted 3 May 1999
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