The effect of crop domestication on root and rhizosphere processes.

Crop domestication brought about many changes in the traits of plants, known as the 'domestication syndrome'. However, the impact of domestication on root processes and the rhizosphere (the soil directly surrounding the roots) remains under-studied. Root exudates and belowground volatile organic compounds (VOC) are involved in a wide range of interactions with plants and abiotic components. They also interact with rhizosphere microbes creating a specific 'rhizosphere effect' which is the difference between the rhizosphere and root-free soil in terms of the microbial community. This aspect of domestication has been overlooked and is important both for understanding the evolutionary process of domestication, and also for improving our current agricultural systems. This project aims to greatly advance our understanding of root and rhizosphere processes in crops and their wild relatives. I will focus on two root processes: (1) root exudation, which is the release of water-soluble organic compounds (including sugars, organic acids and amino acids) from the roots, and (2) root VOC emission (including monoterpenes, sesquiterpenes and isoprene). A few previous studies have demonstrated differences in root exudation and belowground VOC emission between specific wild and cultivated species, providing evidence that it is worthwhile to focus on these root traits in crop wild relatives. However, so far, there has been no systematic comparison of these processes between crops and wild plant species. This project will study, for the first time, the role of exudates, VOCs, and the rhizosphere microbiome in crop domestication. A novel greenhouse screening experiment will be established, allowing the comparison of 20 species from 10 pairs of crops and their wild relatives under controlled conditions. The hypotheses are: (1) wild relatives will have higher rates of root exudation and VOC emissions, per unit root mass, and a higher diversity of exudate compounds compared to crops; (2) crop rhizospheres will have lower diversity of microbes, compared to their wild relatives; (3) the rhizosphere effect will be explained by the quantity and composition of exudates and VOCs. Key measurements will be of root exudation quantity and composition, in situ passive sampling of belowground VOCs and DNA sequencing of rhizosphere bacteria. Result from this project will illuminate the so-far hidden domestication processes, and may guide future crop trait selection. This could include greater or more diverse exudation, or associations with beneficial soil microbes that may help maintain food production in the face of changing climate conditions and degrading soils. The requested funds will pay for the VOC and the DNA sequencing of the soil microbial community.

Keywords:SOIL ECOLOGY, ECOLOGY, PLANT ECOLOGY, CROP PLANTS

Disciplines:Soil ecology, Plant ecology, Plant morphology, anatomy and physiology, Agricultural plant production not elsewhere classified