Catalyzes the reduction of a 3''-keto intermediate during the biosynthesis of 2'-deoxymugineic acid (DMA) from L-Met. Involved in the formation of phytosiderophores (MAs) belonging to the mugineic acid family and required to acquire iron. 2'-deoxymugineate + NAD(+) = 3''-deamino-3''-oxonicotianamine + H(+) + NADH 2'-deoxymugineate + NADP(+) = 3''-deamino-3''-oxonicotianamine + H(+) + NADPH Optimum pH is 8-9. Siderophore biosynthesis. Mostly expressed in root tissues, observed in mesocotyl and embryonic roots, seedling roots, crown and seedling leafes, mature bracts, anthers, pistil, caryopsis and embryos. Up-regulated under iron-deficient conditions in root and shoot tissues. Belongs to the aldo/keto reductase family.