Improvement in the Synthetic Elite NT for soils with low nitrogen content. I. Genetic parameters for yield

Abstract

The objective of this work was to evaluate the maize (Zea mays L.), Elite 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+) nitrogen availability. The experimental design was a 12 x 12 latice with 55,000 plants/hectare. The general mean to ear weight for the families 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 variance was 567.50 (g/pl)², corresponding to 46.62% of the estimate obtained in (N+). The estimate for expected genetic progress in (N-) was of 12.78 g/pl and corresponds to 66% of the estimate found in (N+). The results indicate genetic variability and that selection in environments with nitrogen stress carried out with selection for syncrony of flowering has potential to increase efficiency in a breeding program.