“Purple Stem,” a New Indicator of Soybean Stem Resistance to Bean Flies (Diptera: Agromyzidae)

Abstract
A purple pigment in the stem epidermis of wild soybean, Glycine soja Sieb and Zuec., varieties indicates that the underlying tissue contain specific traits for resistance to the agromyzid bean fly, Ophiomyia centrosematis (de Meijere). The anthocyanidin malvidin was identified as the cause of the purple color. This situation demonstrates interrelationships among this flavonoid and lignins and polyphenols which contribute to insect resistance in the stem of soybean.