NATURAL OCCURRENCE OF FUMONISINS IN RICE WITH FUSARIUM SHEATH ROT DISEASE

Twenty samples of rough rice (Oryza sativa) (unpolished kernels) colle cted during the 1995 harvest season from Arkansas (seven samples) and Texas (13 samples) were obtained from rice fields known to include pla nts with symptoms of Fusarium sheath rot putatively caused by Fusarium proliferatum. Samples were analyzed for fumonisin B-1(FB1) at three l aboratories using three different extracting solvents by high-performa nce liquid chromatography (HPLC) or enzyme-linked immunosorbent assay (ELISA) methods. Forty percent of the samples were positive for FBI at levels less than or equal to 4.3 mu g/g by HPLC. The same samples con tained FBI at less than or equal to 3.6 mu g/g when measured by an ELI SA method. Most samples that were positive for FBI were positive for f umonisin B-2 (FB2) and fumonisin B-3 (FB3) by HPLC at levels less than or equal to 1.2 mu g/g. Very good agreement was obtained among the tw o laboratories using HPLC methods and the third using ELISA. Shelling of the unpolished rice results in hull and brown rice fractions. In a sample that contained 4.3 mu g/g in whole kernels, the fumonisin level was very high in hulls (less than or equal to 16.8 mu g/g) and low in brown rice (less than or equal to 0.9 mu g/g). Milling of brown rice results in bran and white rice fractions. Fumonisins were found in bra n at a level of less than or equal to 3.7 mu g/g but were below the le vel of detection by HPLC in white rice. The presence of fumonisins (FB 1, FB2, and FB3) was confirmed by fast atom bombardment/mass spectrome try. This is the first report of fumonisins in naturally contaminated rice in the United States.