POTENCIAL GENÉTICO DAS POPULAÇÕES DE MILHO UFVM 100 E UFVM 200 AVALIADAS EM SOLOS COM DEFICIÊNCIA DE NITROGÊNIO

The objective of this study was to estimate the genetic potential of two maize populations, in order to verify their genetic potential under two production systems (with and without nitrogen stress). So, 49 half-sib families (FMI) of the population UFVM 100 and 49 FMI of the population UFVM 200 were randomly taken. The 7 x 7 lattice design was used, with two replicates. The high nitrogen level was established with planting fertilization more two side-dressing fertilizations, so totaling 120 kg/ha N (40 kg/ha N in planting fertilization; 40 kg/ha N at the 15 days after emergency - DAE; 40 kg/ha N at 30 DAE). The low nitrogen level was only 20 kg/ha N in planting fertilization. The experimental plot consisted of one row with 5m length and 0.90m spacing between rows and 0.20m among plants inside the rows. All experiments were subjected to water deficit (irrigation interruption) at flowering stage, during 7-day period, until soil water potential was between -0.09 to -0.1 MPa. The grain yield was evaluated in each plot. The variance analysis relative to those 49 FMI of each population in each production system was accomplished according to recommendation by Cochran and Cox (1957), whereas the estimates of the genetic parameters were performed according to method 1 presented by Silva et al. (1999), when considering the lattice experiments. After the individual analyses, those 15% more productive FMI were selected in each production system to estimate the expected selection gain when recombining them. It was found that only the population UFVM 100 shows genetic variability to be explored by selection based on half-sib families, for grain production under low N availability conditions; the estimates of the genetic parameters associated to grain yield were similar as for high and low nitrogen; the consistence of the agreement level between the families´ performances under low and high availability of nitrogen was low, therefore pointing out the need for conducting a specific improvement program when the objective is to obtain material adapted to nitrogen stress conditions.