APPEARANCE OF FUNGUS, ERGOSTEROL AND Fusarium MYCOTOXINS IN THE HUSK, AXIAL STEM AND STALK AFTER EAR INOCULATION OF FIELD CORN

Abstract

(Miller et al. 1983b). This paper reports on the subsequent appearance of the fungus, ergosterol and mycotoxins in the husk, axial stem and stalk. MATERIALS AND METHODS Inoculation and Sampling of CornFull details of the methods used are given by Miller et al. (1983b). In summary, ears of corn were inoculated by a toothpick method with Fusarium graminearum isolate M69 and plants were taken at random at weekly intervals from 2 to 9 wk thereafter. The ears were husked, the plant stalks were cut into 10-cm sections to 50 cm above and below the point of attachment of the ear, and ca. l-mm tansverse slices were removed from the stalk and ear attachment stem (axial stalk) for analysis for fungi. All husks, axial stem and stalk samples were stored frozen ( -l8"C) Moisture and Ash DeterminationsMoisture and ash were determined in duplicate by heating samples (2 g) in a vacuum oven overnight at 60oC and, after measurement of the weight loss, in a muffle furnace (600'C) for 2h. RESULTS HuskThe moisture content of the husk remained constant at ca. 7 6Vo for weeks 2-4 and then decreased to 47Vo by week 9, while the ash content increased considerably (from2.7 to 4.0Vo, on a dry weight basis). Ergosterol levels increased steadily until reaching a maximum (at 370 ppm) at week 6 and then declined by 25Vo over the next 3 wk (Fig. lA). Deoxynivalenol levels reached a maximum (370 ppm) after 6 wk and then plateaued, while 15-acetyldeoxynivalenol levels peaked (59 ppm) at week 3 and then quickly dropped to about l2-15 ppm until harvest (Fig. 1A). Zearalenote remained low (< 0.3 pm) and only began to make a significant appearance in the last few weeks, reaching a maximum (5.2 ppm) at harvest.

Deoxynivalenol and Acetyldeoxynivalenol Accumulation in Field Maize Inoculated with Fusarium graminearum

“…The same metabolites have been detected in all fractions of maize samples. According to other reports (Young and Miller., 1985;Bennett et al, 1988;Perkowski et al, 1991) the highest amounts of DON were present in axial stem. In hybrids examined in this paper, the following DON concentrations were found in axial stem ranged from 153 mg/kg (Ruten) to 1962 mg/kg (RAH BE 86101).…”

“…Accumulation of mentioned metabolites in naturally infected ears have been reported in our previotis papers (Visconti et al, 1990;Perkowski et al, 1991). Miller and Young (1983) and Young and Miller (1985) studied the formation of DON, 15-AcDON and zearalenone in field com in ear and adjacent parts of stalk. They found toxins throughout the plant, but mainly in the infected part (ear).…”

Reaction of winter wheat (Triticum aestivumL.) cultivars to infection withFusariumspp.: mycotoxin contamination in grain and chaff

“…As mentioned above, metabolite penetration into the kernels is limited when humidity is high, when mycotoxins accumulate mostly on the kernels surface. Literature data and our earlier findings (Young and Miller 1985;Perkowski et al 1990) indicated that the outer portions, i.e. chaff and husk, have higher mycotoxin contamination levels, which is an interesting finding with practical implications.…”

Possible Role of Trichothecene Mycotoxins in Virulence of Fusarium graminearum on Maize

“…Trichothecenes apparently are not essential for fungal growth in vitro, because field strains and mutants that do not produce trichothecenes grow as vigorously as trichothecene-producing strains in the laboratory (10). Some studies have suggested that trichothecenes may be translocated in the plant tissues in advance of fungal growth (29,35). As trichothecenes probably act to impair protein synthesis in plants, trichothecenes could suppress or delay the plant defense response against a fungal attack.…”