Progresso genético para produtividade de grãos em um programa de seleção recorrente recíproca em milho

Abstract

Hybridization is the main strategy used by current breeding programs for productivity increases. The success of a hybrid is the result of the cross between two strains that have a good combinatorial capacity, a larger number of favorable alleles, and genetic variability. In this context, the reciprocal recurrent selection method acts to increase these characteristics during the selection cycles. However, there is a constant need to measure and improve the efficiency of the improvement program over the cycles. This verification is also important for program decisions, such as improvement strategies and evaluated characteristics, and can be accomplished by studying genetic progress throughout the cycles of reciprocal recurrent selection. This thesis aims to verify the genetic progress with the reciprocal recurrent selection of the maize breeding program at the Universidade Federal de Lavras (UFLA). The work was conducted during two seasons, summer of 18/19 and winter of 2019. A total of 75 hybrids from the most promising S2: 3 progenies from cycles 0, 3, and 6 of UFLA's reciprocal recurrent maize selection program were evaluated. Two commercial hybrids used by producers in the Lavras region were also evaluated. Productivity, the weight of sheared ear, the weight of 100 grains, ear length, ear diameter, cob diameter, number of rows, number of grains per row, and cob weight were evaluated. The characters were evaluated by joint variance analysis between crop and off-season and by analysis of variance by crop, considering the cycles as a variation factor and diallel analysis by cycle of origin. The joint analysis of variance revealed a genotype x environment interaction. The analysis of variance was not significant at 5% of confidence for the data obtained during the off-season. However, productivity, weight of untucked ear, ear diameter, number of rows, and cob weight were significant at 5 % probability for the harvest. The diallel analysis showed a distinction of superior parents, according to the estimates of the general combining ability, and highlighted hybrids, based on the estimates of specific combining ability, in each cycle of reciprocal recurrent selection. Genetic progress of 7% of gain per cycle was found during the recurrent selection depending on the studies conducted with the adjusted means.