RAPID SCREENING TECHNIQUES FOR LIPOXYGENASES IN SOYBEAN SEEDS

Soybean [Glycine max] breeders are developing cultivars that lack one or more lipoxygenase enzymes for use in certain food products, but electrophoresis for screening lipoxygenase phenotypes in a large segregating population is expensive and time-consuming. Rapid procedures were developed to screen seeds for lipoxygenase-1, -2, and -3, based on the ability of these enzymes at the surface of cut or broken seed to form hydroperoxides when exposed to emulsions containing linoleate or linolenate. The peroxides are detected by a color test based on the oxidation of iodide-starch for lipoxygenase-1 or of ferrous thiocyanate for lipoxygenase-2 and -3. The test for lipoxygenase-3 is valid only in the absence of lipoxygenase-2; all other combinations of lipoxygenases can be tested. For more than a few samples, the new procedures are generally more rapid, convenient, and less costly than electrophoresis and do not require special equipment.