In a context where agricultural practices in Europe are likely to go toward extensive systems with lower inputs, it is important to determine the genetic improvement of winter wheat (Triticum aestivum L.) not only in high‐input agricultural systems but also in low‐input systems. This study assesses the improvement in agronomic traits of winter wheat cultivars cultivated in France during the second half of the 20th century at four agronomic treatments: two levels of fungicide were combined with two levels of nitrogen fertilizer. Fourteen cultivars introduced between 1946 and 1992 were grown for two years (1994 and 1995) at five locations. Selection played a major role in the increase in winter wheat yield after 1946. The contribution of selection to this increase depended on the agronomic treatment and varied from one third to one half. Reduction of height was the most important factor. New cultivars with shorter straw expressed higher harvest index values and more consistent higher yields since they were less susceptible to lodging. The ability to produce more kernels from a given total above‐ground biomass was the second factor. The number of kernels per unit area had increased over time without alteration of the weight of the kernels. The negative relationship between 1000‐kernel weight and kernel number/m2 was therefore shifted and new cultivars were thus able to fill more kernels than older entries. Modern cultivars used N more efficiently than their predecessors. The future challenge will be to obtain, in low‐input systems, the same genetic gains as in high‐input systems.

usually provides more directly comparable information, particularly about yield components. The main results In a context where agricultural practices in Europe are likely to of such studies are given in Table 1. Genetic gains for go toward extensive systems with lower inputs, it is important to determine the genetic improvement of winter wheat (Triticum aesti-grain yield varied from 5.8 kg ha Ϫ1 yr Ϫ1 to 59 kg ha Ϫ1 vum L.) not only in high-input agricultural systems but also in low-yr Ϫ1 . Theses gains represent 33 to 63% of the national input systems. This study assesses the improvement in agronomic M. Brancourt-Hulmel, INRA, Unité de Gé né tique et d'Amé lioration des Plantes, 80200 Estré es-Mons, France; G. Doussinault and M. Trotimproved NUE resulted from either an improved uptet, INRA, Unité de Gé né tique et d'Amé lioration des Plantes, 35650 take efficiency (plant N per unit of N taken up from Le Rheu, France; C. Lecomte, INRA, Station de Gé né tique et d'Amé lthe soil) or a greater N utilization efficiency (grain yield ioration des Plantes,

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