Ganhos diretos, indiretos e simultâneos com a seleção de características agronômicas em genótipos de Urochloa spp.

Abstract

The objective was to evaluate direct, indirect and simultaneous gains of genotypes of the genus Urochloa spp. as to agronomic characteristics in semiarid region and recommend the best genotypes. 27 genotypes of the genus Urochloa spp. including two witnesses to Urochloa brizantha cv. Marandu and the Mulato II hybrid cultivar. The design was in randomized blocks, with three replications, in two agricultural years of evaluations (2018-2019 and 2019-2020). Direct, indirect and simultaneous gains with the selection were estimated. To obtain the simultaneous gains, two indexes were used based on the methodology of Mulamba and Mock (1978). There was significant genotypic variance for total dry weight, dry leaf weight, height, regrowth, percentage of leaves and production in the dry season. All values of the residual variation coefficient were higher than the genotypic variation coefficient, which resulted in relative variation coefficients below 1. The direct selection of the total dry mass and leaves resulted in positive indirect gains in most of the characteristics, except for the leaf: stem ratio. The greatest direct gain with the selection was observed for production in the dry season, which was positively correlated with total dry matter and leaf dry matter. The variables total and leaf dry mass, regrowth and forage in the drought provide greater direct gains with selection. The characteristic forage production in drought is more representative for the selection of individuals with drought tolerance. Individuals T1712, T1709, T1708, Mulato II and BARG153 are more adapted to use in the semiarid region.