Pourazari, F., Vico, G., Ehsanzadeh, P. and Weih, M. 2015. Contrasting growth pattern and nitrogen economy in ancient and modern wheat varieties. Can. J. Plant Sci. 95: 851Á860. Nutrient availability, especially nitrogen (N) availability, is a limiting factor for crop production in many regions of the world. Modern crop varieties often produce high yields under high resource availability, whereas ancient varieties are expected to have characteristics more suitable under low resource availability. To test this expectation, we compared the growth and N use efficiency (NUE) of some varieties of ancient hulled wheat, Triticum turgidum spp. dicoccum, and modern free-threshing wheat, T. aestivum and T. turgidum spp. durum. The wheats were grown under different nutrient fertilization (F) levels in two contrasting environments (field in Iran and outdoor growth container in Sweden). Grain yield was significantly higher in modern varieties than in ancient varieties, regardless of fertilization level. In contrast, N uptake efficiency (i.e., mean N in the plant during the main growth period over N in the initial seed grain) and grain N concentration were generally higher in the ancient varieties. Nitrogen use efficiency, defined as the ratio of the grain N content to the sown seed N content, was higher in the ancient varieties only at lower nutrient supply, because in modern varieties higher nutrient supply resulted in a marked increase in NUE through greatly enhanced grain-specific N efficiency (grain yield per mean plant N content during the main growth period). The modern varieties also showed greater fertilization responses in above-ground biomass and leaf area than ancient varieties. The results are relevant in the context of wheat breeding for nutrient use efficiency. La quantite´de nutriments disponible, particulie`rement l'azote (N), fait partie des facteurs qui limitent la production agricole dans maintes re´gions du monde. Les varie´te´s contemporaines donnent souvent un haut rendement quand les ressources ne manquent pas alors que les varie´te´s anciennes ont des caracte`res qui se preˆtent davantage a`la rare´faction des ressources. Pour le ve´rifier, les auteurs ont compare´la croissance et l'efficacite´de l'utilisation de l'azote (NUE) de quelques varie´te´s de l'antique ble´monde´Triticum turgidum spp. dicoccum et du ble´moderne, sans battage, T. aestivum et T. turgidum spp. durum. Le ble´a e´te´cultive´sous divers re´gimes de fertilisation dans deux milieux contrastants (au champ, en Iran, et dans un conteneur exte´rieur, en Sue`de). Le rendement grainier des varie´te´s modernes e´tait significativement plus e´leve´que celui des varie´te´s anciennes, peu importe le degre´de fertilisation. En revanche, l'efficacite´de l'absorption du N (c.-a`-d. la concentration moyenne de N dans la plante pendant la principale pe´riode de croissance comparativement a`la concentration de N initiale dans la graine) et la concentration de N dans le grain sont ge´ne´ralement plus e´leve´es chez les varie´te´s antiques. La NUE, q...