?tude de l'accumulation et de la remobilisation de l'azote chez l'orge (Hordeum vulgare L): comparaison de vari?t?s poss?dant ou non le g?ne de semi-nanisme (sdw)

Chez l'orge, le g?ne r?cessif sdw (semidwarf) agit sur la morphologie et le d?veloppement de la plante et d?termine le type demi-nain. Il entra?ne ?galement des effets encore mal connus sur l'absorption, l'assimilation et la remobilisation. Or, 80% de la teneur en azote du grain provient du processus de remobilisation. L'objectif de l'exp?rimentation (en plein champ et en pots) est l'?tude de caract?ristiques agrophysiologiques d'un cultivar distique semi-nain, F?dora en comparaison avec 2 cultivars de taille normale (absence de l'all?le sdw), Sonia (type 2 rangs) et Plaisant (type 6 rangs). Il ressort que la vari?t? semi-naine pr?sente une importante capacit? de tallage. Dans les conditions de notre exp?rimentation, la vari?t? semi-naine assimile de fa?on efficace l'azote du sol et remobilise moins bien les substances azot?es vers le grain que les vari?t?s normales. Dans le cas de l'orge brassicole Plaisant, qui pr?sente pourtant une forte remobilisation, on observe une faible teneur en prot?ines du grain (comparable ? celle de F?dora) qui semble essentiellement due ? un stockage moins important de l'azote dans les parties v?g?tatives. Investigation on nitrogen accumulation and remobilization in barley (Hordeum vulgare L) : comparison of varieties with or without the semi-dwarfing gene (sdw). In barley, the sdw dwarfing gene has a strong effect on morphology and development but also on nitrogen absorption, assimilation and remobilization (the latter contributes 80% to final grain nitrogen content). The aim of this work (carried out under both field and semi-controlled conditions) was to study some agrophysiological characteristics of a semi-dwarf cultivar (Fedora : 2 rows), compared with 2 cultivars without the sdw gene (Sonia : 2 rows and Plaisant: 6 rows). Our results clearly indicated that tillering capacity was higher in the semi-dwarf cultivar. On the other hand, higher nitrogen assimilation and lower remobilization efficiency were noted when the sdw gene was present. In spite of a high translocation rate, the malting variety Plaisant showed a grain protein content as low as that observed in Fedora; this could be due to a low nitrogen absorption. Effects of the semi-dwarfing gene on productivity, nitrogen partitioning and grain protein content are finally discussed for their contribution to brewing quality in breeding programs.