Análise dialélica, estimativas de parâmetros genéticos e seleção de genótipos de soja

Abstract

The evaluation of the genetic potential of parents to obtain superior segregating populations, as well as the estimation of genetic parameters and correlations and the choice of selection method are essential tools in breeding programs for the development of superior soybean cultivars. This dissertation was divided into three chapters. Namely, the first theoretical reference chapter that deals with general aspects of soybean cultivation, genetic improvement, selection of parents and diallels, estimates of genetic parameters and selection strategies. The second chapter aimed to estimate the general (CGC) and specific combining ability (CEC) of five soybean parents, through partial diallel, in order to identify the most promising parents and hybrid combinations for precocity and yield of soybean grains. The experiments were carried out in the Soybean Genetic Improvement Program at UFU in Uberlândia - MG. Fifteen genotypes were evaluated, 10 F2 progenies from diallel crosses and 5 parents (UFUS 7010; IAC Foscarin-31; UFUS 7101; TMG 803 and BRS 511). Through diallel analysis, it can be concluded that the parents IAC Foscarin-31 and BRS 511 contribute to greater precocity, while TMG 803 to greater grain yield, therefore, they were considered genetically superior and indicated to participate in crosses. The most promising combinations for grain yield and agronomic traits were IAC Foscarin-31 ⨉ TMG 803, UFUS 7101 ⨉ TMG 803 and UFUS 7010 ⨉ BRS 511. The third chapter aimed to estimate genetic parameters and correlations in four RCF3:4 segregating soybean populations and to select the superior progenies for precocity and productivity. Fifty-two progenies from four segregating populations were sown: PS-A: (UFUS 7010 ⨉ TMG 801) ⨉ TMG 801 with 10 progenies; PS-B: (UFUS 7010 ⨉ TMG 801) ⨉ UFUS 7010 with 11 progenies; PS-C: (UFUS 7010 ⨉ BRSGO 7560) ⨉ BRSG 7560 with 16 progenies; PS-D: (UFUS 7010 x BRSGO 7560) ⨉ UFUS 7010 with 15 progenies. Fifteen superior RCF3:4 progenies were selected for earliness and grain yield through the genotype-ideotype distance index: G2, G6, G13, G15, G20, G21, G29, G33, G36, G38, G39, G42, G48, G51 and G52. In all experiments, 15 agronomic and production characters were evaluated.