IMPROVEMENT IN THE SYNTHETIC ELITE NT FOR SOILS WITH LOW NITROGEN-CONTENT - I - GENETIC-PARAMETERS FOR YIELD

The objective of this work was to evaluate the maize (Zea mays L.), El ite Synthetic NT, selected in soils with low nitrogen availability (N- ) and with male-female synchrony (ASI), and to make estimations of its genetic parameters for yield. During the 1994/95 season, 144 half-sib families were evaluated in environments with low (N-) and high (N+) n itrogen availability. The experimental design was a 12 x 12 latice wit h 55,000 plants/hectare. The general mean to ear weight for the famili es in the (N+) and (N-) environments was 4,511 and 3,237 kg of ears/ha , respectively. Yield reduction between (N+) and (N-) environments was 27.14% for the half-sib families and 65.80% for the intercalar check BR 106. The analysis of variance showed-significance for treatments in both environments (P < 0.01). In (N-) the estimate for additive varia nce was 567.50 (g/pl)(2), corresponding to 46.62% of the estimate obta ined in (N+). The estimate for expected genetic progress in (N-) was o f 12.78 g/pl and corresponds to 66% of the estimate found in (N+). The results indicate genetic variability and that selection in environmen ts with nitrogen stress carried out with selection for synchrony of fl owering has potential to increase efficiency in a breeding program.