Caracterização de linhagens endogâmicas recombinantes do cruzamento entre BRS Querência x BRS Bojuru em arroz irrigado

Abstract

Rice (Oryza sativa L.) presents an important role in worldwide agriculture, since more than 90% of rice grown belongs to this species. In the world ranking of cereal production, Brazil is the largest producer outside Asia. In the national scenario, Rio Grande do Sul stands out as the state that produces the most rice, being responsible for more than 70% of production. One of the main objectives in crop breeding programs is the increase in yield potential of cultivars, being necessary to identify superior genotypes within the program. One of the alternatives for the identification of useful genetic variability is the accomplishment of crosses involving contrasting parents and to generate segregating populations. Most agronomic traits of economic importance have quantitative inheritance and their contribution to genetic gains can be maximized by the analysis of the structure and genetic potential of the segregating population. Thus, this work aimed to evaluate the segregation of rice F6 progenies and their parents in order to identify transgressive families for the evaluated agronomic traits, besides estimating the genetic components and parameters that help to intensify the understanding of the genetic base of these traits and finally to predict selection gains through selection methods among families, within families, mass and combined at the selection pressures of 15% and 25%. This study was performed in the year 2016/2017, where 65 families from the cross between the cultivars BRS Querência (Oryza sativa ssp. indica) and BRS Bojuru (Oryza sativa ssp. japonica) were evaluated, the generation advances were made in the experimental field of Embrapa Clima Temperado (ETB), in the County of Capão do Leão-RS, until the F6 generation. The design was in lines with intercalary parents, arranged in 4 repetitions. It was possible to observe the transgressive segregation of the families in both senses and for all the evaluated agronomic traits, indicating variability to proceed to the selection. When estimating the genetic parameters, heritability coefficients were verified in the strict sense among the families, of higher order, therefore indicating the efficiency for selection between the families. Among the selection methods adopted, the combined selection at a 15% pressure allowed higher selection gains for all evaluated traits, except for plant stature, since this one selected plants below the desired average. For plant size it is recommended the selection method between families.