Análise dialélica de genitores de soja visando precocidade, produtividade e teores de proteína e óleo

Abstract

The careful selection of parents through combining ability methods, as well as the estimation of genetic parameters and correlations, constitute fundamental tools in breeding programs to identify segregating populations with high genetic potential and to ensure the development of superior soybean cultivars. This thesis was divided into three chapters in the article format. The first chapter aimed to evaluate the combining ability of five soybean parents for agronomic traits and protein and oil contents, with the objective of identifying promising combinations for the extraction of superior lines. The trials were conducted in Uberlândia (MG) in the 2022/23 (F3 generation) and 2023/24 (F4 generation) growing seasons, involving the parents UFUS 7010, UFUS 7101, IAC Foscarin-31, TMG 803, and BRS 511. Through diallel analysis, it was concluded that the parents IAC Foscarin-31 and BRS 511 contribute to earlier maturity and higher protein content, while TMG 803 favors productivity, and UFUS 7101 increases oil content. The most promising combinations for earliness and grain yield were TMG 803 × BRS 511 and IAC Foscarin-31 × TMG 803, whereas the combination IAC Foscarin-31 × BRS 511 stood out for increasing protein content. The second chapter aimed to estimate the combining ability of nine soybean parents through a partial diallel and to identify promising segregating combinations for agronomic traits. The trials were conducted in Uberlândia-MG in the 2023/24 (F2) and 2024/25 (F3) growing seasons, using a partial diallel between five elite genotypes (UFUS 7010, UFUS 7101, UFUS 7201, UFUS 7910, and UFUS 8401) and four genotypes serving as sources of resistance to the soybean cyst nematode (TMG 2381 IPRO, TMG 4182, BRS 7380 RR, and BRS 7581 RR). Additive gene effects predominated, indicating that the parents UFUS 7201, UFUS 8401, TMG 2381 IPRO, and TMG 4182 provided the greatest gains for yield and number of pods. The most promising combinations for obtaining superior genotypes with high productive potential were UFUS 7101 × TMG 2381 IPRO, UFUS 7910 × TMG 2381 IPRO, and UFUS 7910 × TMG 4182. The third chapter aimed to estimate genetic parameters in segregating populations and to select those with the highest potential for earliness, grain yield, and protein and oil content. Eight segregating populations and six parents were evaluated in the early generations (F2, F3, and F4), conducted in Uberlândia (MG) between the 2021/22 and 2023/24 growing seasons. The analyses showed significant genetic variability and high-magnitude heritabilities for cycle and biochemical quality. The populations UFUS 4 (for earliness and oil), UFUS 7 (for protein), and UFUS 8 (for productivity, medium cycle, and oil) stood out as the most promising for the extraction of superior genotypes. In all experiments, phenological, agronomic, yield components, and grain biochemical quality traits were evaluated.