Rhizosphere Functional Phenomics: Using High-Throughput Phenotyping to Understand Root-Soil Interactions.

Hiltner originally defined the rhizosphere as the soil influenced by plant roots. However, soil physicists, chemists, microbiologists, and plant physiologists have studied the rhizosphere independently, and therefore conceptualized the rhizosphere in different ways and using contrasting terminology. Rather than research-specific conceptions of the rhizosphere, the authors propose a holistic rhizosphere encapsulating the following components: microbial community gradients, macroorganisms, mucigel, volumes of soil structure modification, and depletion or accumulation zones of nutrients, water, root exudates, volatiles, and gases. A model of the rhizosphere using partial differential equations is proposed to offer a conceptual framework of rhizosphere interactions for future work. This framework will be necessary for designing crop ideotypes capable of stable production in a changing world.

Roots are the interface between plant and soil, but remain a largely untapped source of phenotypic variation for improving crops. Quantifying root phenomes requires deconstruction of complex phenotypes into more elemental units, or phenes, followed by high-throughput phenotyping. Linking root phenes to function is rarely attempted, yet is undoubtedly crucial for generating crop ideotypes targeting specific environments. This seminar will explore root functional phenomics by first discussing the fundamental processes of soil water and nutrient flux as related to root uptake. High-throughput phenotyping of roots in the field will be discussed for a variety of species that represent the diversity of plant root system architecture. Maize represents cereals with apical dominance, wheat represents tillering cereals, and soybean represents dicots with taproot dominated systems. Ideotype development, phenotyping, simulation modelling, and functional assays in the field constitute a powerful functional phenomics pipeline capable of increasing our basic understanding of how the rhizosphere develops, gene discovery, and increasing the nutrient and water use efficiency of the world’s dominant crops.