Iron tolerance in rice: an efficient method for performing quick early genotype screening.

OBJECTIVES: This study was conducted to establish a method for early, quick and cheap screening of iron excess tolerance in rice (Oryza sativa L.) cultivars. RESULTS: Based on the experiments, iron excess leads to reduction in shoot length (SL) and this can be a useful characteristic for adequate screening of tolerant genotypes. The sensitive genotypes Nipponbare and BR-IRGA 409 indicated higher accumulation of iron in their tissues while BRS-Agrisul and Epagri 108 also accumulated iron, but at lower concentrations. BR-IRGA 410 displayed an intermediate phenotype regarding iron accumulation. No changes in shoot Cu content can be observed when comparing treatments. On the other hand, an increase was seen for Zn and Mn when shoots are subjected to Fe2+ excess. Fe stress at a lower concentration than 7 mM increased Zn but decreased Mn contents in shoots of BR-IRGA 409. Strong positive correlations were found here for Fe × Zn (0.93); Fe × Mn (0.97) and Zn × Mn (0.92), probably due to the Fe-induced activation of bivalent cation transporters. Results show that genotypes scored as sensitive present higher concentration of Fe in shoots and this is an efficient method to characterize rice cultivars regarding iron response.

Resíduos de azevém na superfície de um Planossolo alagado e seus efeitos na concentração de nutrientes na solução do solo e em plantas de arroz / Ryegrass residues on soil surface of a flooded Albaqualf soil and their effects on nutrients concentration in soil solution and rice plants

A incorporação de resíduos de culturas ao solo em lavouras de arroz irrigado tem o potencial de melhorar as características físicas, químicas e biológicas do solo e acelerar as reações de oxirredução durante o alagamento, proporcionando maior disponibilidade de nutrientes para as plantas, que respondem com maior crescimento e maior absorção de nutrientes. Com o objetivo de determinar a concentração de nutrientes na solução do solo e quantificar a absorção de nutrientes e o crescimento de plantas de arroz submetidas a quantidades crescentes de resíduos de azevém aplicadas na superfície do solo, foi conduzido um experimento em casa de vegetação. O experimento foi delineado em blocos ao acaso, com três repetições, sendo utilizadas como tratamentos doses de resíduos de azevém (0,0; 1,25; 2,5; 5,0; 7,5 e 10,0Mg ha-1) aplicadas na superfície de um Planossolo. Sementes de arroz pré-germinadas da cultivar 'BRS 7 Taim' foram semeadas na superfície do solo, que foi alagado 15 dias após, e as plantas foram cultivadas por um período de 45 dias. Nas plantas de arroz, foram avaliados a massa seca da parte aérea e os teores dos nutrientes: N, K, P, Ca, Mg, Fe, Mn, Cu e Zn. Na solução do solo, foram avaliados o potencial redox (Eh), o pH e as concentrações de Mn, Fe, K, Ca e Mg. Os resultados mostraram que a adição de doses crescentes de resíduos de azevém na superfície do solo alagado, até a dose máxima de 10Mg ha-1, intensificou o processo de oxirredução do solo, aumentando a concentração de Mn, Fe, Ca, Mg e K na solução do solo, aumentou os teores de K e Fe na parte aérea das plantas de arroz e aumentou a massa seca de arroz.

The incorporation of ryegrass residues on the soil in rice irrigated fields can improve the physical, chemical and biological soil properties. It can also accelerate the redox reaction during the soil flooding, allowing a higher availability of nutrients to the plants, which responds with a higher growing and nutrient absorptions. The objectives of this research are to quantify the nutrient absorptions, the rice crop growing, and to determine the concentration of nutrients in the soil solution on a flooding Albaqualf soil. For this, increasing doses of ryegrass residues were applied in the soil surface. A greenhouse experiment was carried out using a randomized complete block design with six doses of ryegrass residues (0.0; 1.25; 2.5; 5.0; 7.5 and 10.0Mg ha-1) applied to the soil surface. Cultivar 'BRS 7 Taim' pre-germinated seeds were sown in plastic pots. The soil in the pots was flooded 15 days after this procedure and plants were hept in this condition for an additional 45 days. In the rice plants were evaluated the dry matter weight of the shoots and the following nutrients: N, K, P, Ca, Mg, Fe, Mn, Cu and Zn. In the soil solution were evaluated the redox potential (Eh), pH, and the concentration of Mn, Fe, K, Ca, Mg. Results show that the addition of increasing doses of ryegrass residues in the flooded soil surface until 10Mg ha-1 strengthened the soil redox reaction process increasing the concentration of Mn, Fe, Ca, Mg and K in the soil solution. It also increased the K and Fe contents in the aerial part of rice plants as well increased their dry matter weight.