Effect of climatic conditions on natural mycoflora and fumonisins in freshly harvested corn of the State of Parana, Brazil

Natural mycoflora associated with fumonisins were analyzed in 150 samples o f freshly harvested corn from Central-Southern, Central-Western and Norther n regions of the State of Parana, Brazil and correlated to climatic conditi ons. The corn samples were frequently contaminated with Fusarium sp. (98.7 to 100%) and Penicillium sp. (93 to 100%), when compared to Aspergillus sp. (not detected to 27.7%). The highest contamination with potentially mycoto xigenic fungi occurred in corn harvested in the Central-Western region, whe re total mould and yeast counts ranged from 5.5 x 10(3) to 5.2 x 10(6) CFU/ g, with 98.7% contaminated by Fusarium sp. and 93% by Penicillium sp. In th is region F. moniliforme ( F. verticillioides) was the predominant Fusarium sp., and was isolated in 85.9% of the samples. Aspergillus sp. was isolate d from 27.7% samples. FB1 was detected in 100% of the samples (mean of 2.39 mu g/g) and FB2 in 97.7% (mean of 1.09 mu g/g). Fumonisins were also detec ted in all samples from Northern region, with mean of 4.56 mu g/g (FB1) and 2.20 mu g/g (FB2). Considering 1.0 mu g/g as the threshold, 72% of the cor n samples from the Central-West and 92% from the North were contaminated wi th concentrations above this value, in contrast to a 18.5% contamination ra te from Central-Southern samples. Between corn planting to harvesting seaso n, the average maximum temperature and relative humidity were 26 degrees C and 77.1% (Central-Southern), 27 degrees C and 69% (Northern) and 29.9 degr ees C and 89.1% (Central-Western). Therefore, the higher fumonisins contami nation of corn from Northern region when compared to the Central-South were due to the differences in rainfall levels (92.8 mm in Central-Southern, 20 2 mm in Northern) during the month preceding harvest.