Análise dialélica, correlações e divergência genética em soja para fins de seleção de genitores

Abstract

Population projections predict an accelerated and continuous growth in the next decades, until the year 2050, whose estimates reach 9.5 billion people, consequently increasing the demand for food. Thus, an increase in the global consumption of soy is expected, since the legume is an important supplier of oils and proteins and is present in animal and human food. Currently, Brazil is the largest soy exporter in the world, thanks to investments in technologies and genetic improvement programs. The development of new soybean cultivars is an ongoing process, aiming to create new genotypes with high grain yield, precocity and resistance to disease. Some steps are fundamental in this process, such as choosing parents, performing hybridizations and selecting superior progenies. Thus, diallel analysis is an important tool, which allows the estimation of the general and specific combining ability of parents. The present work aimed to determine the general and specific combining ability in soybean, aiming to identify progenitors and promising combinations for the UFU genetic improvement program; to analyze the genetic dissimilarity of soybean genotypes in RCF3 and F4 using agronomic phenotypic characters and vegetative phase descriptors. Two experiments were carried out under greenhouse conditions, located in the experimental area of Fazenda do Glória, belonging to the Federal University of Uberlândia, in Uberlândia, Minas Gerais. In the first experiment, 6 hybrids were obtained by crossing four soybean cultivars in a 4x4 partial diallel scheme. The segregating population F2 was seeded together with the four parents in a randomized block design (RBD) with ten replications. Vegetative and agronomic phase characters were evaluated and it was concluded that the partial diallel analysis in soybean in the F2 generation allowed us to determine that the BRS GO 7560 and UFUS GUARÁ cultivars are the potential parents for crop cycle reduction, increase in the number of pods and grain production. Promising crosses for vegetative and agronomic phase characters were BRS 511 x UFUS GUARÁ and BRS GO 7560 x TMG 801. In the second experiment 32 soybean progenies in F4 generation and 17 RCF3 progenies from the cross between BRS 7380RR and TMG genotypes were sown. 1179 RR from the Soy Improvement Program at the Federal University of Uberlândia. Then, the dissimilarity estimate between the evaluated genotypes was carried out, and later grouped by different hierarchical optimization methods in order to identify the genetic diversity between the genotypes. The genotypes showed genetic divergence from each other by means of intragroup mean linkage, Tocher grouping and principal components. The characters that most contributed to genetic diversity were the number of days to flowering, the number of nodes in the main stem at flowering, grain yield and hypocotyl length, which were estimated by the criterion of Singh (Sj) (1981) surpassed 9%. Considering the genetic divergence and the early genotypes and still with a high number of three-grain pods and grain yield, it was possible to indicate the combinations: BMX Desafio RR x UFU 10, BMX Desafio RR x UFU 14, BMX Desafio RR x UFU 49 and BMX Challenge RR x UFU 25.