How can we harness quantitative genetic variation in crop root systems for agricultural improvement?

Abstract

Root systems are a black box obscuring a comprehensive understanding of plant function, from the ecosystem scale down to the individual. In particular, a lack of knowledge about the genetic mechanisms and environmental effects that condition root system growth hinders our ability to develop the next generation of crop plants for improved agricultural productivity and sustainability. We discuss how the methods and metrics we use to quantify root systems can affect our ability to understand them, how we can bridge knowledge gaps and accelerate the derivation of structure-function relationships for roots, and why a detailed mechanistic understanding of root growth and function will be important for future agricultural gains.Keywords: Architecture; genetics; imaging; quantification; root Citation: Topp CN, Bray AL, Ellis NA, Liu Z (2016) How can we harness quantitative genetic variation in crop root systems for agricultural improvement?.

Convergent evolution of root system architecture in two independently evolved lineages of weedy rice

“…Below‐ground root growth and spatial organisation of root systems can be described in terms of root system architecture (RSA) (Topp et al ., ). Despite its critical role in determining efficiency of soil nutrient and water uptake, as well as neighbour‐to‐neighbour communication and levels of plant competition, RSA is far less characterised than above‐ground aspects of plant growth (Casper & Jackson, ; Topp et al ., ). To the extent that the genetics of RSA have been examined, this has mostly been at the level of QTL mapping, in which many loci have been identified in crop varieties (Uga et al ., ; Topp et al ., ).…”

The quest for understanding phenotypic variation via integrated approaches in the field environment

“…High-throughput soil coring (Wasson et al, 2014), root crown excavation (Das et al, 2015), and minirhizotron analysis (Maeght et al, 2013) are common ways in which roots are studied in the field, but each provides limited information relative to the actual root structure. Thus, there remains a lack of a coherent view of root phenotypes and their genetic and environmental conditioning (Topp et al, 2016). An ideal technology would allow the explicit in situ visualization of root architecture as it develops through time and likely would involve sensors that were either aboveground or located belowground with minimum invasiveness.…”

Hope in Change: The Role of Root Plasticity in Crop Yield Stability

“…Their various use of lysimeters, soil cores, and rhizoscopes also illustrates the rather piecemeal and limited way in which roots must currently be measured, especially in agriculturally relevant contexts. The parable of the blind men and the elephant is apt for root phenotyping, as each method we use captures only some small, and often incongruous, slice of information about the true phenotype (Topp et al, 2016). What's easier to see is that a highly resolved knowledge of the genetic and mechanistic basis of root architecture plasticity will allow us to speed the pace of crop improvement toward varieties that will be both robust and sustainable in future, uncertain climates.…”