GENETIC PROGRESS IN 20 YEARS OF RECIPROCAL RECURRENT SELECTION IN MAIZE
Maize, a grain distinguished globally for its economic relevance, has experienced a large increase in yield in the past decades. Breeding programs, which are largely responsible for crop development, aim at using techniques that maximize profits and are in accordance with local demand. The full-sib reciprocal recurrent selection (RRS) has a long-term focus on producing better performing hybrids. On this basis, this study intended to evaluate the development of reciprocal populations (Piranão and CIMMYT) throughout ten RRS cycles, in terms of genetic progress, and to verify the occurrence of heterosis and its magnitude. To this end, each of the ten selection cycles, represented by three genotypes (Piranão genotypes, CIMMYT genotypes, and interpopulation hybrids) were tested in four trials, in two locations, and in two years, in a 14x20 alpha-lattice with four replicates. The traits evaluated were grain yield, ear weight, and prolificacy. There was a major increase for all traits in interpopulation hybrids, even though the CIMMYT parent had not shown a significant increase, suggesting that even though one of the populations stagnates after 10 cycles, RRS is efficient in obtaining superior hybrids. There was an average increase of 171 kg.ha-1.cycle-1 throughout the ten cycles. Heterosis and heterobeltiosis oscillated between cycles, with higher mean for heterosis, suggesting discrepancy between the parents and superiority of the Piranão population (possibility to indicate the increase in yield per cycle or per year).