Prevention of fumonisin contamination in corn.

Species of the genus Fusarium are the moulds most frequently found on cereal crops in temperate regions. Many of these species possess the ability to produce mycotoxins, a diverse group of substances toxic to humans and animals. Fumonisins are a family of mycotoxins that are predominantly found in corn and their main producers are F. verticillioides and F. proliferatum. These mycotoxins have been classified as a "possibly carcinogenic agent in humans" by the International Agency for Research on Cancer and their maximum levels have been defined in food for human and animal consumption in the European Union and in other countries.

In Galicia, despite the existence of a favourable climate for the development of moulds, the presence of mycotoxigenic species or contamination with mycotoxins in corn or other cereals has hardly been investigated. Currently, there is no concrete information on what environmental and/or genotypic factors determine the level of fungal infection and the fumonisin content in grains at harvest time. This knowledge is important and necessary when assessing risk and making decisions to prevent contamination with fumonisins. For this reason, in the present work we have studied which are these factors, the weight that each one of them has and at what moments throughout the cultivation period are critical for infection by F. verticillioides and contamination with fumonisins of corn kernels. The degree of presence of other Fusarium species in the grains has also been determined to assess the risk of contamination with other mycotoxins. At the same time, it has been sought to find out how environmental, biotic and abiotic factors influence the process of fungal infection and accumulation of fumonisins throughout the physiological development and drying of the grain in the field. Finally, and in parallel, the resistance to fumonisin accumulation of four white corn hybrids was evaluated after artificial inoculation with a local isolate of F. verticillioides.

As a result of this work, we can confirm that F. verticillioides is the most abundant species and the main producer of fumonisins in corn grains grown in Pontevedra. Less frequently, other mycotoxigenic species of the genus Fusarium were detected, so there is a potential risk of contamination with other mycotoxins. Late plantings and early harvests were less favourable for infection by F. verticillioides, its development and the accumulation of fumonisins in the grains, so its application is recommended to reduce contamination with these mycotoxins. It was observed that fumonisin contamination was especially influenced by environmental conditions during flowering and during grain drying. It is necessary to be cautious when the climatic conditions during flowering are drier and hotter, and try to avoid (through early harvests) heavy rainfall before harvest, as well as greater damages to the grains (caused mainly by insects). The use of varieties with some resistance to moths, to the borer and with good bract coverage can be a useful tool to reduce the risk of contamination with fumonisins.

Throughout the development of the grains, the significant increase in the concentration of fumonisins occurred from physiological maturity and during field drying. This increase was favoured by the decrease in temperatures and by fungal growth, favoured, in turn, by moth damage, and indicating that, in addition to the state of development of the grain, local environmental conditions during field drying can be decisive in the accumulation of fumonisins.

Finally, the standard behaviour of the local isolate of F. verticillioides and its ability to produce fumonisins has been verified, and the partial resistance of the white corn hybrid EP10 x EC22 to the accumulation of fumonisins in the grains has been confirmed by artificial inoculation.