Estimativa de parâmetros genéticos para caracteres agronômicos e avaliação da qualidade fisiológica de sementes em duas populações F2 de soja

Abstract

Obtaining more productive genotypes of soybean cultivation is one of the main objectives of breeding programs. There are few studies on the selection of agronomic traits associated with the quality and performance of soybean seeds. The objective of this work was to estimate genetic parameters of agronomic traits, seed quality and grain yield in soybean segregating populations, from parents with different seed quality history. The following cultivars were used to obtain segregant populations: NS 7200 RR, NS 7670 RR and UFUS 6901. The crossing block was installed in a greenhouse, with the following combinations: (1) UFUS 6901 x NS 7200 RR and (2) UFUS 6901 x NS 7670 RR. From the artificial hybridizations the F1 seeds were generated, which were harvested and seeded again to obtain the F2 seeds by means of their self-fertilization. F2 seeds were sown in the field, by sowing in pits. For the combination 1, 66 seeds of cultivar UFUS 6901, 62 seeds of cultivar NS 7200 RR and 203 seeds of generation F2 were seeded. For the combination 2, were seeded 64 seeds of cultivar UFUS 6901, 64 seeds of cultivar NS 7670 RR and 230 seeds of generation F2. Agronomic traits were evaluated in all individuals: number of days for flowering (NDF) and maturity (NDM), plant height at flowering (PHF) and maturity (PHM), number of nodes at flowering (NNF) and maturity (NNM), height of first pod insertion (HPI), number of grains per pod (NGP), production of grains (PG) and weight of a thousand grains (WTG). Data were analyzed by means of analysis of generations and estimated the genetic parameters. For the three parental and both segregant populations, the physiological quality of the seed was evaluated by germination, germination and primary root length and fresh and dry matter of seedlings. The emergence and emergence speed index was also analyzed in a greenhouse under a sand bed. The physiological seed quality data were submitted to analysis of variance and, afterwards, submitted to the Tukey average test. Genetic-statistical analyzes were performed in the Genes Program (CRUZ, 2016). All the characters under study had medium to low heritability results, and the highest results were obtained for APF and WTG in the two combinations, being influenced by five and three genes, respectively. F2 populations have transgressive segregants for all the characters, except for NDM in combination 2. The combinations 1 and 2 allow the selection of superior individuals to be obtained in terms of precocity, height, number of nodes and productivity components, being promising genotypes in a soybean breeding program. The segregating populations did not present superior results in relation to the parents as to seed quality.