Indirect versus direct selection of winter wheat for low-input or high-input levels

Market prices and environmental concerns favor low-input wheat (Triticum aestivum L.) production systems. This study assesses the efficiency of low-input vs. high-input selection environments to improve wheat for low-input environments. Three standard cultivars, 11 parents, and 270 lines bred in INRA Mons-Peronne were investigated for 2 yr (1998, 1999) in France at three INRA locations. Four agronomic treatments combining two levels of fungicides with two levels of nitrogen (N) were applied. Because of seed supply, only 10 year x treatment x location combinations were conducted. Broad-sense heritabilities for grain yield (GY) ranged from 0.18 at low N without fungicide to 0.90 at high N without fungicide. Heritability estimates were higher at high N than at low N level. This was due to both an increase in error variance and a decrease in genetic variance at low nitrogen level. Heritabilities in treatments without fungicide were the same or higher than heritabilities measured in the corresponding controlled treatments. Broad-sense heritabilities for grain N content (GNC) were similar between the controlled treatments with fungicide and the corresponding treatments without fungicide. They were lower at low N level and this was due to an increased error variance in both years. Genetic correlations between the 10 experiments were always positive for GY and N content: they ranged from 0.10 to 0.95 for yield and from 0.78 to 0.98 for GNC. The relative efficiency of indirect selection to direct selection for each pair of environments ranged from 0.15 to 0.99 indicating that indirect selection was never more efficient than direct selection. Therefore, breeding programs targeting low-input environments should include low-input selection environments to maximize selection gains.