Breeding progress in grain yield of winter wheat cultivars grown at different nitrogen levels in semiarid conditions

Abstract

The objectives of this study were to estimate the progress in wheat genetic yield potential, associated with changes in some agronomic traits, under different N rates. Twenty-four cultivars of winter wheat (T. aestivtum L.) representing most of the cultivars released in Serbia from 1955 to 2006 were analyzed. The cultivars were grown for four years (2005-2008) in field trails with two levels of agronomic inputs (low nitrogen-N-45 and high nitrogen-N-110). Data were collected on 1000-kernel weight, kernels per spike, kernels per square meter, spikes per square meter, plant height, harvest index, heading time and grain yield. Mean difference between the two fertilization levels was 0.44 t ha(-1). The average rate of increase in yield potential per year of release, estimated from the slope, was 41 kg ha(-1) year(-1) and it was significantly different from zero (P lt = 0.01). It was 35 kg ha(-1) year(-1) or 0.55% at the low level of N input, and 46 kg ha(-1) year(-1) or 0.68% at the high level of N input. This suggests that modern cultivars are better adapted to high N input. Our results suggested that individual contribution of the most of analyzed traits may vary depending on the genotype as well as environmental conditions.