Viabilidade da seleção precoce para o peso de mil grãos em populações segregantes de soja

Abstract

Grain yield in soybean is a complex quantitative trait determined by the interaction among different yield components, such as thousand grain weight, number of pods per plant, and number of grains per pod. Based on the hypothesis that the use of parents with high thousand grain weight in crosses may positively influence the expression of this trait and yield components in segregating populations, the objective of this study was to evaluate grain yield and the contribution of its main components in soybean populations derived from crosses between parents with different levels of thousand grain weight. The experiment was conducted at the Experimental Station of Inova Genética LTDA, located in Porto Nacional, Tocantins, Brazil, using an experimental design suitable for evaluating segregating populations, including commercial checks. The segregating populations were classified according to the type of cross (high × high, high × medium, and high × low). The evaluated traits were thousand grain weight, grain yield, number of pods per plant, and number of grains per pod. The analyses included comparison of means among groups, estimation of genetic parameters (variance components and heritability), Pearson correlation analysis, and geometric analysis of the relative contribution of yield components. The results showed that the type of cross significantly influenced thousand grain weight and grain yield, with a decreasing trend in thousand grain weight as the average value of the parents decreased. However, thousand grain weight exhibited low heritability, indicating strong environmental influence. In contrast, the number of pods per plant and number of grains per pod showed high heritability, indicating greater genetic control. Correlation analysis revealed a weak association between thousand grain weight and grain yield, whereas the number of grains showed a stronger relationship with yield. The geometric analysis indicated that superior genotypes present a balance among yield components rather than the maximization of a single trait, suggesting the occurrence of compensatory mechanisms. It is concluded that soybean grain yield is determined primarily by the balance among its yield components. Among the ten highest-yielding populations, six originate from crosses between parents with high thousand-grain weight (TGW) and medium thousand-grain weight. These results contribute to understanding yield architecture and help define more efficient strategies in soybean breeding programs.