Co-occurrence of aflatoxin and fumonisin in maize under site-specific nitrogen

FANTINI, E.; GIAJ-MERLERA, G.; REYNOSO, M.M; TORRES, A.M.

Rotterdam,

Simposio; 7th Conference of The World Mycotoxin Forum and XIII IUPAC International Symposium on Mycotoxins and Phycotoxins; 2012

IUPAC

Maize is one of the most important cereal grains produced in Argentina. In the last decade the country has positioned as the sixth producer in the world and the second world exporter. Precision agriculture has the potential to adjust fertilizer rates according to soil types and/or other defined conditions within management zones. The aim of this work was to determine the effect of site-specific nitrogen rates to fumonisin and aflatoxin contamination on maize in natural infection conditions. For this purpose two on-farm trials were set up in 2011-2012 crop season, in Córdoba Province. The trials were done using a strip trial design where N rates were varied (site-specific) and uniform along strips (0 to 400 kg N ha-1) in replicated strips along the length of each field (500 m). Measurements of the yields were carried out with a yield monitor placed in a combine harvester. At harvest time, sampling was done to evaluate the presence of mycotoxigenic fungi and mycotoxins in maize grain. Fumonisin B1 (FB1), and fumonisin B2 (FB2), were measured by precolumn derivatization with o-phthalaldehyde followed by separation on reversed-phase column. Aflatoxins were separated and determined by reversed-phase LC with fluorescence detection after pre-column derivatization with trifluoroacetic acid. Aspergillus section flavi were the most abundant species detected in maize kernels in Adelia Maria field, and Fusarium spp. were detected in both locations. The level of fungal contamination was no depending on the fertilization rate. The level of aflatoxin in Adelia Maria varied between 8.6 and 516.0 ppb, while in Alejandro Roca the toxin was no detected. This high level of aflatoxin are unexpected because is not common to detect the toxin in corn filed samples in Argentina.  Fumonisin contamination in samples from Alejandro Roca was approximately 2-fold higher than those from Adelia Maria, with the level varied from 3983 to 14039 ppb.  Fumonisins not show a clear relationship to N fertilization rate. When the climatic conditions favored aflatoxin production, the levels of contamination in the grain were independent of fertilizer rate.