Transgenic rice lines that include barley genes have increased tolerance to low iron availability in a calcareous paddy soil

Iron (Fe) deficiency stress is a widespread problem in agriculture and must be overcome to increase crop yields, particularly in calcareous soils. Unlike barley, rice, one of the three major crops in the world, is very susceptible to low Fe availability because of a low capacity to secrete mugineic acid family phytosiderophores (MAs), which are Fe chelators secreted by graminaceous plants. We tested three transgenic rice lines possessing three barley genes involved in MAs synthesis in a field experiment on a calcareous soil under paddy conditions. Two rice lines, one with a barley gene encoding nicotianamine synthase (NAS) and the other with a barley gene encoding a dioxygenase, referred to as Fe-deficiency specific clone no. 3 (IDS3), showed higher tolerance to low Fe availability under these conditions. The rice line with the IDS3 gene also had increased concentrations of Fe and zinc (Zn) in the grains. These results show that introducing barley genes involved in the synthesis of MAs into rice is an effective and practical method to improve agricultural productivity in calcareous soils.