Seleção recorrente na população CNA9 de arroz de terras altas para tolerância e responsividade ao fósforo

• Autor(a) principal: Vidotti, Miriam Suzane
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/4860
• topic: Oryza sativa L.; Genética quantitativa; Estresse abiótico; Componentes de variância; Melhoramento populacional; Oryza sativa L.; Quantitative genetics; Abiotic stress; Variance components; Breeding population; GENETICA::GENETICA VEGETAL

The upland rice has a high potential for expansion in the Brazilian savannahs region, where soils have limiting factors to yields, such as low phosphorus (P) availability. Considering the costs and the natural reserves scarcity, a suitable alternative is to explore the genetic resources to develop cultivars with P deficiency tolerance and P-use efficiency. Given the polygenic inheritance of these traits, a strategy is to concentrate the favorable alleles gradually through recurrent selection. The objectives of this study were to estimate genetic and phenotypic parameters, and evaluate progenies from CNA9/3/1 recurrent selection population of upland rice for the tolerance to P deficiency in the soil. In 2011/12 crop year, in Santo Antônio de Goiás-GO and Sinop-MT, two contrasting trials were conducted within each location: low and high P-level determined by the clay content of the soil, and without discrimination of other crop practices. The simple square lattice design 14 x 14 was adopted, with 189 S0:2 progenies and seven checks, with plots consisted of four 3-m-long rows. Grain yield (GY, in kg ha-1), plant height (PH, cm) and days-to-flowering (DF, in days) were evaluated. The individual variance analysis by location and by P-level were obtained, well as their phenotypic, genetic and environmental correlations. Only for PG, genetic and phenotypic parameters were estimated from joint analysis of variance within each P-level, and involving locations and P-levels. Estimates of the expected response to selection were obtained for the two P-levels, considering the direct, indirect and general selection criteria, and also the Harmonic Mean of Relative Performance () and Tolerance Index () of the genotypes identified as efficient and responsive from a graphic dispersion of adjusted means. The overall average of the GY was reduced significantly in 27% for P deficiency in the soil and the genetic variance among S0:2 progenies (̂ 2) was narrowed in 63%. Highly significant diferences (p≤0.01) were observed among progenies, demonstrating the presence of sufficient genetic variability for GY, in this population, to obtain genetic progress in both P-levels. The progenies showed performance significantly (p≤0.01) below the of checks and also a significant interaction (p≤0.01) with locations, in both P-levels. The genotype x Plevel interaction was significant (p≤0.01) and the phenotypic correlation (√R2) between Plevels was low (0.44). In this sense, the expected response to selection demonstrated that progenies must be evaluated in P-deficient environments to obtain effective genetic gain in this environment. The genetic correlations between traits were significant (p≤0.01) and are favorable for the selection of genotypes with tolerance to P deficiency, short plant height and early cycle. However, there is a greater difficulty in increasing the yield potencial, since there the genetic correlation between this trait and PH was significant (p≤0.01) and positive (= 0.385). From the graphic dispersion of S0:2 progeny means have been identified 57 efficient and responsive to the presence of P in the soil, and for the selection within this group, the was more appropriate than , because considering simultaneously these two attributes.