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 Siderophore biosynthesis. Mostly expressed in root tissues, observed, at low levels, in mesocotyl and embryonic roots, seedling roots, crown and seedling leafes, mature bracts, anthers, pistil, caryopsis and embryos. Belongs to the aldo/keto reductase family.