Fusaria andFusariummycotoxins in leaves and ears of maize plants 2. A time course study made in the Waikato region, New Zealand, in 1997

摘要

The patterns of fungal infection and mycotoxin contamination in leaf and ear sections of plants of two maize(Zea maysL.) 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 beingFusarium.Most common in leaf fractions wereEpicoccum, Fusarium,andAlter#x2010;naria,whereas in ear fractions the most common wereFusarium, Penicillium, Cladosporium,andMucor.The most common fusaria isolated from leaf fractions were the toxigenic speciesF. crookwellenseandF. graminearum.These species were evident from late February although other, non#x2010;toxigenic, species were present in leaf axils from early January. For ear fractions the most common species wereF. graminearum, F. crookwellense,andF. subglutinans. Fusariuminfection was evident in ears of P3902 from March to April, although heavy infection by the toxigenic species tended to occur later towards May#x2010;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 toxigenicFusariumspecies 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#x2013;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 byFusariumin New Zealand may not be controlled by factors at silk emergence but rather by later season events such as high rainfall and warmer temperatures.