A scanner system for high-resolution quantification of variation in root growth dynamics of Brassica rapa genotypes

Abstract

The potential exists to breed for root system architectures that optimize resource acquisition. However, this requires the ability to screen root system development quantitatively, with high resolution, in as natural an environment as possible, with high throughput. This paper describes the construction of a low-cost, high-resolution root phenotyping platform, requiring no sophisticated equipment and adaptable to most laboratory and glasshouse environments, and its application to quantify environmental and temporal variation in root traits between genotypes of Brassica rapa L. Plants were supplied with a complete nutrient solution through the wick of a germination paper. Images of root systems were acquired without manual intervention, over extended periods, using multiple scanners controlled by customized software. Mixed-effects models were used to describe the sources of variation in root traits contributing to root system architecture estimated from digital images. It was calculated that between one and 43 replicates would be required to detect a significant difference (95% CI 50% difference between traits). Broad-sense heritability was highest for shoot biomass traits (>0.60), intermediate (0.25–0.60) for the length and diameter of primary roots and lateral root branching density on the primary root, and lower (<0.25) for other root traits. Models demonstrate that root traits show temporal variations of various types. The phenotyping platform described here can be used to quantify environmental and temporal variation in traits contributing to root system architecture in B. rapa and can be extended to screen the large populations required for breeding for efficient resource acquisition.

Accelerating genetic gains in legumes for the development of prosperous smallholder agriculture: integrating genomics, phenotyping, systems modelling and agronomy

“…• Low-cost, high-resolution root phenotyping platform, requiring no sophisticated equipment and adaptable to most laboratory and glasshouse environments, and applied to quantify environmental and temporal variation in root traits Adu et al (2014) The Plant Accelerator® (The University of Adelaide, Australia)…”

A scanner-based rhizobox system enabling the quantification of root system development and response of <i>Brassica rapa</i> seedlings to external P availability

“…The sources of variation in static root traits (i.e. root traits measured on the last day of the experiment) were determined using a mixed effects model as described by Adu et al (2014). The run, scanner and genotype were considered as random factors using Supplemental equation S2.…”

“…1A). Root growth was routinely monitored and captured with ArchiScan which has been installed on a computer directory on which there is sufficient space to save images (Adu et al 2014(Adu et al , 2015, http:// www.archiroot.org.uk). ArchiScan is fully parameterizable software which allows the management of several scanners for scheduled remote root growth acquisitions.…”

“…For these reasons, various rooting media have been used. Rooting media such as agar or gels (Jain et al 2009, Yazdanbakhsh and Fisahn 2012, Gruber et al 2013, Shi et al 2013) and paper pouches (Liao et al 2001, Hammond et al 2009, Hund et al 2009, Adu et al 2014, 2015, 2016 is generic and can be used with any scanner provided a TWAIN driver is available. The number of scanners per computer depends on the number of plants to be screened, duration of experiment, frequency of scanning and the computers' storage capacity.…”

“…Problems with the initial lighting were basis for our choice of the later lighting system. We opted for the 100 W cool-white fluorescent tubes because the distance between plants the light was short and as a result, the original lamps (the Philips SON-T Agro 400-W high pressure sodium lamp) produced excessive heat and condensation on the scanner system (Adu et al 2014(Adu et al , 2015 to study the root growth dynamics of Brassica rapa L. seedlings grown in rhizoboxes.…”