The carcinogen, aflatoxin B1 (AFB1) produced by Aspergillus flavus, is a major food safety concern in crops. However, information on AFB1 occurrence in soil and crop residue is scarce. A series of experiments investigated the occurrence of AFB1 in soil and corn residues, and ascertained the ecology of A. flavus in a Dundee silt loam soil. Samples of untilled soil (0 to 2 cm) and residues were collected in March 2007 from plots previously planted with a corn isoline containing the Bacillus thurengiensis endotoxin gene (Bt) or the parental non-Bt isoline. Aflatoxin B1 levels were significantly different in various corn residues. The highest AFB1 levels were observed in cobs containing grain, with 145 and 275 ng g-1, in Bt and non-Bt, respectively (Pr ≥ F = 0.001). Aflatoxin levels averaged 3.3 and 9.6 ng g-1 in leaves/stalks and cobs without grain, respectively. All soils had AFB1 ranging from 0.6 to 5.5 ng g-1 with similar levels in plots from Bt and non-Bt corn. Based on cultural methods, soil contained from log (10) 3.1 to 4.5 A. flavus CFU g-1 with about 60% of isolates producing aflatoxin. Laboratory experiments demonstrated that AFB1 is rapidly degraded in soil at 28oC (half-life ≤ 5 days). The potential of the soil A. flavus to produce aflatoxins was confirmed by molecular methods. Transcription of five aflatoxin biosynthesis genes including afllD, aflG, aflP, aflR and aflS were detected by RT-PCR analysis in soil. Although AFB1 appears to be transient in soils, it is clear that AFB1 is produced in surface soil in the presence of corn residues as indicated by A. flavus CFU levels, AFB1 detection, and expression of aflatoxin biosynthetic genes.

Aspergillus flavus occurence and expression of biosynthesis genes in soil

ACCINELLI, CESARE;
2008

Abstract

The carcinogen, aflatoxin B1 (AFB1) produced by Aspergillus flavus, is a major food safety concern in crops. However, information on AFB1 occurrence in soil and crop residue is scarce. A series of experiments investigated the occurrence of AFB1 in soil and corn residues, and ascertained the ecology of A. flavus in a Dundee silt loam soil. Samples of untilled soil (0 to 2 cm) and residues were collected in March 2007 from plots previously planted with a corn isoline containing the Bacillus thurengiensis endotoxin gene (Bt) or the parental non-Bt isoline. Aflatoxin B1 levels were significantly different in various corn residues. The highest AFB1 levels were observed in cobs containing grain, with 145 and 275 ng g-1, in Bt and non-Bt, respectively (Pr ≥ F = 0.001). Aflatoxin levels averaged 3.3 and 9.6 ng g-1 in leaves/stalks and cobs without grain, respectively. All soils had AFB1 ranging from 0.6 to 5.5 ng g-1 with similar levels in plots from Bt and non-Bt corn. Based on cultural methods, soil contained from log (10) 3.1 to 4.5 A. flavus CFU g-1 with about 60% of isolates producing aflatoxin. Laboratory experiments demonstrated that AFB1 is rapidly degraded in soil at 28oC (half-life ≤ 5 days). The potential of the soil A. flavus to produce aflatoxins was confirmed by molecular methods. Transcription of five aflatoxin biosynthesis genes including afllD, aflG, aflP, aflR and aflS were detected by RT-PCR analysis in soil. Although AFB1 appears to be transient in soils, it is clear that AFB1 is produced in surface soil in the presence of corn residues as indicated by A. flavus CFU levels, AFB1 detection, and expression of aflatoxin biosynthetic genes.
2008
Accinelli C.; Abbas H.K.; Zablotowicz R.M.; Wilkinson J.R.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/127573
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