Rice interspecific hybrid NERICA4 shows extremely high tolerance to excess iron and salinity in the rhizosphere

Soil salinity and excess iron are major abiotic stresses that limit global plant growth and productivity. However, the response of NERICA4 rice, which is a high-yielding and interspecific hybrid developed by crossing O. sativa and O. glaberrima to these abiotic stresses occurring in rain-fed paddy fields, has not been demonstrated. In a completely randomized design, we evaluated the effects of salinity (0, 50, and 100 mM NaCl) and excess iron (0, 250, 500, and 750 mg L−1 FeSO4) on NERICA4 and susceptible and tolerant control rice varieties at the seedling stage. NERICA4 was highly responsive to osmotic stress, as the leaf blade water potential was maintained even under high salt stress (100 mM NaCl). A low shoot Na+/K+ ratio under salt stress suggests that Na+ may be eliminated by the root system, supporting its salt-tolerance ability. NERICA4 presented low root and shoot iron ion concentrations across all the iron treatments, suggesting that it might inhibit iron uptake under iron-rich conditions. In conclusion, our research will play a significant role in the introduction and dissemination of the NERICA4 cultivar in the rainfed-rice growing regions of Africa, where soil problems are common.