Tolerance and Phenotypic Analysis of Irrigated Rice Genotypes under Iron Toxicity

Abstract

Introduction: The development of tolerant rice genotypes is the main tool to minimize the problem caused by the excess of iron in the soil.
 Aims: The study aims to evaluate the response of genotypes of the Embrapa breeding program of irrigated rice against iron stress, as well as to envision the relationship of the effect of this disorder on leaf mass production in different phenological phases of the plant.
 Study Design: The trial was established in a randomized block design with additional controls, with the plots consisting of four rows 3 m long with 0.20 m spacing between rows.
 Place and Duration of Study: The experiment was conducted in the experimental field of Embrapa Temperate Climate Lowlands Station, in a period of nine years, consisting of the harvest of 2006/2007 until 2014/2015.
 Methodology: It was evaluated 255 lines along with 4 additional control cultivars with known tolerance levels. The symptoms were evaluated at 40, 70 and 100 days after plant emergence through a visual assessment in the field, based on the standard evaluation system for rice. In addition to the determination of the average toxicity levels of genotypes, the mass was collected, constituted by the dry matter of shoot, for the detection of interrelationships through their correlations.
 Results: It was found that 58.82% of the developed irrigated rice lines show good tolerance to toxicity by excess iron. The association of the content of dry matter of shoots and the levels of indirect toxicity of iron showed a significant negative correlation (-0.6848), being that the highest magnitude of negative correlation was at 70 DAE (-0.6161).
 Conclusion: There is variability for tolerance to indirect iron toxicity between the irrigated rice genotypes assessed. The breeding program of irrigated rice of Embrapa has been effective in developing genotypes with tolerance by excess iron in the soil over nine years. There is a negative association between the content of dry matter of shoots and the levels of indirect iron toxicity.