The rhizosheath: from desert plants adaptation to crop breeding

Background First discovered on desert plants by Volkens1887, rhizosheath formation, i.e. soil aggregation at the root surface, is now considered as a very promising adaptive trait to deal with abiotic stress. Indeed, the rhizosheath could help plants better cope with water stress, nitrogen and phosphorus deficiencies, and soil acidity. Scope We have reviewed studies on the biological factors involved in rhizosheath formation, the methods used to quantify it, and its importance in plant nutrition. Thus, we have collected recent evidence that shows that the rhizosheath is an important trait arising from the morphology and physiology of plant root system, and the cooperation between plant root and its associated microbiota. In particular, the transformation of root exudates by exopolysaccharide-producing bacteria effectively contributes to soil aggregation and thus to increases the volume of the rhizosheath (i.e. root-adhering soil), thereby improving the absorption of minerals and water by plants. The growing interest for this process has led to the genetic mapping of potential plant QTLs controlling this trait in order to provide new tools for the selection of plant varieties with improved tolerance to abiotic stresses. Conclusion Finally, we discussed some important issues that need to be addressed in order to develop an appropriate selection strategy focused on the rhizosheath, such as the relationship between the genes controlling rhizosheath formation and those controlling other root traits, but also the impact of rhizosheath formation on soil carbon sequestration, a potential strategy for mitigating climate change.