EFS12- Book of abstracts - Contact

SESSION 2: SECONDARY METABOLITES – BIOCHEMISTRY,
BIOSYNTHESIS, FEED AND FOOD SAFETY
Ecological role of mycotoxins produced by Fusarium
graminearum
M. Abid 1 , L. Fayolle 1 , C. Héraud 1 , P. Mangin 2 , L. Falchetto 2 , N. Gautheron 1 , J.
Laurent 1 , E. Gautheron 1 , V. Edel-Hermann 1 , C. Steinberg 1
1 INRA, UMR1347 Agroécologie 17 rue Sully, BP 86510, F-21000 Dijon, France; 2 INRA, UE Domaine
d’Epoisses, F-21110 Bretenières, France
E-mail: christian.steinberg@dijon.inra.fr
Fusarium graminearum is a plant pathogenic fungus, producing mycotoxins some
of which remain in the crop residues let in the field after harvest. Whether the
presence of mycotoxins in the crop residues gives an advantage to F.
graminearum to survive and develop a primary inoculum in the presence of the
whole soil biota including fungi, bacteria, protozoa, nematodes and earthworms
was tested. The impact of deoxynivalenol (DON) on the soil communities was
evaluated in the field and in microcosms, in wheat and in maize residues under
tillage and no-tillage conditions. The disease development and the yield were
noted in the field experiment. Some DON resistant active fungal decomposers
and nitrogen fixing bacteria were picked and the dynamics of F. graminearum was
observed in their presence, in the presence or absence of DON.
DON in crop residues had an impact on the biotic components of the soil but the
impact depended on the communities and on the location of the residues. The
molecular biomass showed that fungal and bacterial densities were significantly
affected by DON. The latter played significant role on the structure of bacterial
and protozoan community while the nematodes and fungal communities remained
unaffected. However, the minimal inhibitory concentration tests revealed that the
susceptibility of some competitive fungal strains to DON was dose-dependent.
Earthworms (Lumbricus terrestris) were not affected by the presence of
mycotoxin. The degradation of DON in the residues was dependent on the time,
the location of residues and the soil biota.
Obviously DON gave no advantage for the survival and development of primary
inoculum during the decomposition of crop residues in the soil. Moreover fungal
decomposers can be selected on their enzymatic potential towards organic matter
more than on the DON resistance to increase the degradation of the straw left at
the surface and limit the subsequent development of F. graminearum.
Keywords: Biological control, habitat, soil ecology, saprophytic phase
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