GENETIC-IMPROVEMENT ON GRAIN-YIELD OF WHEAT CULTIVARS RELEASED BETWEEN 1940 AND 1992

In 1992 and 1993, at the National Wheat Research Center (CNPT-EMBRAPA), this study was carried out to evaluate the genetic improvement of wheat (Triticum aestivum, L.) cultivars. Fifteen genotypes released between 1940 acid 1992 were evaluated on two nitrogen levels. Linear regression of grain yield means on number of years elapsed since 1940, showed increases of 17 kg/ha(-1)/year(-1) in grain yield, and the newer genotypes showed to be more responsive to higher nitrogen fertilization. The newer genotypes showed a slight increase in the biological yield over the old ones, but the harvest index contributed with 83.6% of the overall yield. There was a significant and positive correlation between grain yield, spikes/m(-2), grain/spike(-1), biological yield and plant dry weight at anthesis. The newer genotypes were shorter in height and grain filling period and had a longer emergence-anthesis period.