Parâmetros genéticos e fenotípicos associados à precocidade em soja

Abstract

Soybean cropping in spring-summer seasons in succession with maize in a second cropping season is notably one of the best options for annual cropping system in Brazil. In order to maintain this system, some characteristics, especially of the predecessor crop, are desirable. With soybean as a reference, the breeding programs have as focus the development of early-maturity genotypes, allowing the successor crop to be sown and cultivated in better water supply availability. The estimation of genetic and phenotypic parameters associated to early-maturity character in soybean has a great importance to breeding programs as it allows guidance to future strategies, since these estimates aid the decision making process in the management of segregating populations and progenies selection.For this purpose, the goals of this study were to evaluate the agronomic performance of segregating soybean progenies; to estimate the genetic and phenotypic parameters associated to early-maturity character in soybean; and to select progenies that associate early-maturity and good agronomic performance, adapted to the cropping conditions of the southern region of Minas Gerais State. F3:4 and F3:5 progenies from four different populations were evaluated. The F3:4 progenies were evaluated in Lavras and Itutinga cities, during the crop year of 2016/2017. Each plot consisted of one row of 1.5 m with two replications, in a 12 x 12 Simple Lattice design (136 progenies and 8 controls). The F3:5 progenies were evaluated in Lavras, Ijaci and Itutinga cities, during the crop year of 2017/2018. Each plot consisted of one row of 3.0 m with three replications, in an 8 x 8 Triple Lattice design (56 progenies and 8 controls). The characters absolute maturity, days to flowering, and grain yield were evaluated. Data analysis were performed considering Mixed Models method using R software. The genetic and phenotypic parameters, the expected and obtained selection gain, the correlated selection response, and progeniesrelative maturitywere estimated, as well as the adjusted means of the progenies for each character. The presence of genetic variability among the evaluated progenies for all three characterswas observed, being possible to obtain success with superior genotypes selection. The genotypes x environments interaction was significant to all evaluated characters. The selection of early-maturity progenies, results in reduction of days to flowering character, however, it was verified reduction of their grain yield potential as well. The magnitudes of the adjusted means for each progeny indicate the possibility of select progenies that associate early-maturity and good agronomic performance, adapted to cropping conditions of the southern region of Minas Gerais State.