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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.

Measurements of proton NMR relaxation times as well as inelastic and elastic neutron scattering of tetraphenyltin (C 6 H 5 ) 4 Sn as a function of temperature and pressure were performed in the work. It allowed to determine activation volume j V * for a small amplitude reorientation/oscillation of the phenyl rings. The values of activation volume is very small and the ratio of j V */ V M ( V M is molar volume) is less than 1%.

Proton NMR relaxation measurements were performed for ammonium bromide at pressures up to 800 MPa. The correlation functions for ammonium ion reorientation were calculated by Monte Carlo method. Knowledge of these functions allow calculation of the NMR relaxation times T1. Comparison between experimental and calculated values of relaxation times gives some insight into the model of ammonium ion reorientation.

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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.

rotating frame (B1= 2.1 mT) were studied for polycrystalline tetraphenyltin Sn(C6H5)4in a wide temperaturerange. Two kinds of motions were detected: isotropic rotation of whole molecules and reorientations/oscillations of phenyl rings. A dependence of the potential energy of the molecule in the crystalon the angle of the phenyl ring rotation about the Sn-C bond was obtained on the basis of atom-atomcalculations. The amplitude of the ring-oscillations at 133 K was estimated as ± 7°. Below room temperaturethe magnetisation recovery is significantly non-exponential, which may be interpreted as dueto the correlated motion of phenyl rings.

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.

The proton NMR second moment and spin-lattice relaxation time for tetrapropylammonium bromide and iodide have been measured over a wide temperature range. A solid-solid phase transition related to the onset of cation tumbling was found for both salts and confirmed by DTA. In the low temperature phases methyl group reorientation was evidenced. For iodide a dynamic nonequivalence of the methyl groups and the onset of ethyl groups motion was also discovered