The Sahel low agricultural yields are gone due to poor soils, drought and rainfall variability. Knowledge and understanding of the interactive effects of drought and nitrogen fertilization on growth of millet appear important. For this purpose the SOUNA3 millet was used as an experimental split-plot with two factors and four replications during the dry season in 2002. The water regime factor was used at two levels (watered and water-stressed) and the nitrogen fertilization factor also at two levels (without nitrogen, F0 and with a nitrogen supply of 68.5 kg ha-1, F1). The water-stressed was applied during the vegetative stage and the grain formation and filling phases. The values of water consumption, the plant water status and the leaf area index were measure during the plant growth. The above dry matter was calculated at each development stage. Yield was calculated at the end of cycle. The results of the water consumption of plants and leaf water potential showed that water stress has reduced the values of these parameters and no difference was showed between nitrogen fertilization treatments whatever the level considered water regime. As for the values of leaf area index and the above dry biomass production, they were higher in fertilized plants for a given water regime. The nitrogen increased the values of these parameters at the irrigated plants. The water deficit has reduced the yield of 52.79 % in stressed plants. The water deficit cancels the beneficial effect of nitrogen fertilization on millet growth and yield.

The impact of plant developmental stage on resistance to rice yellow mottle virus was assessed with a virulent isolate of the virus RYMV. Tests were conducted under controlled conditions at Africa Rice research center. Seed of two rice cultivar were sown at regular intervals in order to produce plant at different age at 35, 49, 63, 77 and 91 days after sowing (DAS) corresponding respectively to the beginning of tillering, active tillering, the end of tillering, panicle initiation and flowering. The inoculum was prepared by grinding 60 g of rice yellow mottle virus infected leaves with 1000 ml of distilled water in a mortar washed with alcohol. The plants were inoculated manually by rubbing the leaves from the leaf base to the tip with fingers moistened with inoculum. Visual leaf chlorosis, chlorophyll (SPAD), virus content and yield reductions due to RYMV were evaluated. Result showed that the two rice cultivars Bouake 189 and CT9153-11-7-1-1 were more susceptible when inoculated at 35 and 49 days after sowing (DAS), attaining up with 99 % and 93% yield loss respectively for the two rice cultivar at 35 DAS. When inoculated at 63 DAS, these cultivar were observed to have developed partial resistance and became total resistance at 91 DAS attaining up 3% yield loss.