Résumé
Water and mineral nutrients availability in soils limit agricultural productivity in many regions of the world. Plants have developed root adaptive strategies to increase hydromineral uptake. Among those, the adhesion of soil particles to plant roots (rhizosheath formation) supposedly contributes to water and nutrient stress tolerance. Consequently, the selection of cultivars with enhanced soil aggregation or the adoption of practices likely to favour this aggregation are potential lever to promote sustainable and resilient agriculture. In pearl millet, intraspecific genetic diversity was observed for soil aggregation as well as root architecture traits. Differences in root soil aggregation were correlated with changes in the composition and diversity of rhizosphere bacterial communities. In addition, correlation was reported between the level of soil aggregation and the intensity of some enzymatic activities in pearl millet plants grown in the field. Here, we analysed the contribution of soil aggregation to water stress tolerance in pearl millet. The study was carried out on 8 recombinant pearl millet lines with contrasted root soil aggregation. Plants were subjected to two levels of water stress for 2 weeks: (1) a partial water stress where daily watering was reduced by half and (2) a total water stress where water supply was stopped 3 weeks after planting. In parallel, a control well-watered treatment was introduced in the experiment. Plants were grown for 35 days in a nethouse. We observed that the intensity of water stress was inversely correlated with the majority of physiological parameters measured. In the same context of water stress, soil aggregation was positively correlated with soil moisture, plant biomass, leaf water potential, and root traits (p-value <0.0001). Our results show that rhizosphere aggregation is likely an asset that enables the plant to cope with water shortages and thus maintain optimum development. However, these results need to be confirmed in the field at different developmental stages and on different varieties.