Genetic differences for nitrogen uptake and nitrogen utilisation efficiencies in winter wheat

Due to economic and ecological factors, European agricultural practices are likely to go towards extensive systems with lower inputs of nitrogen (N) fertilisers. The objective of this study waste assess varietal differences for N use at two nitrogen levels. A set of 20 winter wheat (Triticum aestivum L.) genotypes was studied over 2 years in northern France on a deep loam soil without (NO) and with 170 kg ha(-1) N fertiliser (N +)as ammonium nitrate. Results were consistent on both years as the genotype x year or genotype x year x N level interactions were not significant. The genotype x N level interaction was highly significant except for total N utilisation efficiency (total above-ground dry weight/total above-ground N) and grain N concentration. The genotype x N level interaction for grain yield was mainly due to three contrasting genotypes: Cappelle, a cultivar from the 1940s, had the same yield at NO and N +; Arche had a high yield at both N levels; and Recital had a high yield with added N and a very low one without N. The number of kernels/ear explained most of the variations of grain yield at NO (48%) and N + (80%), and of the interaction (67%). N uptake efficiency (total above-ground N/soil N supply) accounted for 64% of the variation in N use efficiency (grain yield/soil N supply), while at NO and at N + it accounted for only 30%. N utilisation efficiency (grain yield/total above-ground N) was then more important at N + than at NO. Grain N explained most of total plant N variation at both N levels. The interaction for N use efficiency was best explained by the interaction of N uptake (63%). The applications of these results to a breeding programme to create varieties adapted to low-input management systems are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.