Mycoflora and occurrence of fumonisins in freshly harvested and stored hybrid maize

Abstract

The study of the mycoflora in stored grain permits an evaluation of cereal storage conditions that affect grain deterioration and the risk of mycotoxin contamination. Abiotic factors can directly affect the relative frequency of fungal populations in stored grain. The aim of the present work was to study the influence of abiotic factors on variations of mycoflora of freshly harvested and stored maize in Brazil and the occurrence of fumonisins. Samples (195) of three hybrids of maize were analyzed monthly during one year. Microbiological analysis revealed a predominance of Fusarium spp, which presented the greatest total number of colony forming units per gram in the three hybrids, namely: Br 201 (11×10 4 to 5340×10 4 CFU/g), C 125 (18×10 4 to 2790×10 4 CFU/g) and Cx 322 (25×10 4 to 2940×10 4 CFU/g), followed by Penicillium spp, Aspergillus spp and 10 other fungal genera. Fusarium moniliforme Sheldon was the most prevalent species (59.2% of Fusarium isolates in Br 201, 55.4% in C 125 and 69.2% in Cx 322). Fusarium spp showed significant negative correlations with mean temperature and relative humidity of the air. Higher temperatures and relative humidity at the end of the study and high moisture content at the beginning of the study were observed. The CFU/g values recorded for the three predominant genera exceeded the internationally accepted tolerance limits. The mycotoxicological evaluation indicated contamination of 176 samples (90.2%) with fumonisin B 1 and of 190 samples (97.4%) with fumonisin B 2.