Abstract
Iron toxicity is a major nutritional disorder in rice plants, especially in flooded areas. The use of alternative crop management practices, such as soil drainage, may mitigate negative impacts of iron toxicity, since soil aeration that follows drainage can oxidize and precipitate potentially toxic Fe+2 into Fe3+. This study aimed to evaluate the impact of alternative water management on agronomical and physiological parameters in rice plants grown in a field location with iron toxicity history. Rice cultivars BR-IRGA 409 (sensitive) and IRGA 425 (resistant to iron toxicity) were tested. Irrigation management comprised three treatments: continuous irrigation, one cycle of water suppression (1S) and two cycles of water suppression (2S). Evaluations included the ionic composition of soil solution and leaf tissues, grain yield, antioxidant responses and gene expression. Permanent soil flooding resulted in higher grain yield in plants from the resistant than from the sensitive genotype, which had higher malondialdehyde (MDA) concentrations in leaves. In contrast, two cycles of alternate soil drying resulted in equivalent grain yield and MDA concentrations in both genotypes. Resistance to iron toxicity in IRGA 425 plants seems related to limited Fe translocation to shoots, increased tolerance to oxidative stress in leaves and higher expression of Ferritin, OsGAP1, OsWRKY80 and Oryzain-α genes. Plants from the BR-IRGA 409 cultivar (sensitive to Fe toxicity) improved growth and yield under the interrupted irrigation treatments, probably due to lower Fe availability in the soil solution. Management of water irrigation successfully alleviated Fe toxicity in rice plants cultivated in field conditions.
Highlights
Iron (Fe) is an essential micronutrient for plants, being required for fundamental biochemical activities and cellular functions, such as photosynthesis, respiration, DNA synthesis and repair
Plant visual observation revealed that IRGA 425 plants did not suffer apparent damage due to iron toxicity, while plants from the BR-IRGA 409 cultivar showed clear signs of chlorosis under continuous irrigation
The rice grain yield of cultivar BR-IRGA 409 was significantly increased by the treatments with interrupted irrigation: a major increase in productivity was observed in the 2S treatment in relation to Continuous Irrigation (CI) (Fig. 1B), reaching productivity levels equivalent to the ones seen in the resistant cultivar, IRGA 425, which was not affected by the treatments
Summary
Iron (Fe) is an essential micronutrient for plants, being required for fundamental biochemical activities and cellular functions, such as photosynthesis, respiration, DNA synthesis and repair. Iron toxicity in lowland rice (Oryza sativa L.) is a nutritional disorder that affects the production of this cereal in several rice-producing regions worldwide. It occurs most frequently in acid soils rich in sulphate and iron oxide, where, due to the anoxic environment and to the chemical reactions that occur after flooding, reduced iron (Fe2+) becomes soluble and available to plants at high concentrations. Under these conditions, Fe can be excessively absorbed by plants (Ponnamperuma 1972)
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