Relevant aspects regarding the characteristics of the parents and progenies for artificial hybridization of soybean
Genetic improvement of soybean involves various biometric techniques and genomic tools. Controlled hybridization is an indispensable tool of the researcher; however, considering the complexity of the process, floral sensitivity and a strong effect of environmental conditions, the procedure is difficult to control. The objective of this work was to define the optimal periods for artificial hybridization of soybean, in order to maximize the number of seeds formed, and to understand the relationships between the agronomic characteristics of the parents and progenies. The study was carried out in Campos Borges, Rio Grande do Sul, Brazil, during the agricultural years of 2013, 2014, 2015, 2016, 2017 and 2018. The crosses were made during the initial period of flowering of the culture in the greenhouse, totaling 498 directed crosses. There was considerable variability in the number of crosses successfully made, in seed number and viability, and in the crossing index. The efficiency of obtaining heterozygous soybean seeds was 13.8% using planned crosses under controlled conditions. The optimum period to maximize the number of seeds was from 8:15 to 9:45 AM, the number of seeds being inversely proportional to the advance in the day hours. The flower color and the growth habit of the parents express a similar tendency as the time of the cross is determinant for the success of this stage of breeding.