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Institutional changes in Benin have brought to light farmers' demand for varieties better suited to local growing conditions than existing ones. In response, we initiated a participatory cotton breeding experiment in 1996 to evaluate the relevance of such a methodology for the improvement of a commercial crop grown under rain-fed, semi-intensive cropping systems. This paper compares the performance of the first four mass-selection cycles, implemented by three farmer-breeders (F-B) and one formal breeder, with the original population and two commercial controls over three sites and two years. First results show that genetic changes occurred in all the F-B populations. The highest yielding F-B population (Savalou) was also more exuberant and later maturing than the others. Within the relatively narrow range of environments considered in the trial, there is no evidence that decentralized breeding results in better local adaptation. In Benin, participatory cotton breeding may be considered as complementary to formal on-station breeding and useful for enlarging the genetic variability offered to the farmers. Although the farmers want the approach to be scaled-up, its sustainability relies on a formal partnership between research and farmers institutions.

Monte Carlo simulation of correlation functions for ammonium bromide have been carried out and the NMR relaxation times T1resulting from these functions were calculated. Results of simulations are compared to experimental values of T1measured in the temperature range 92 K to 292 K.

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.