Easy-to-build rhizobox method to support wheat root research and breeding for future production systems

Abstract Aims Rhizoboxes allow non-invasive phenotyping of root systems and are often used as an alternative to evaluation in the field which typically requires excavation, a laborious endeavour. Semi-automated rhizobox methods can be used to screen large numbers of plants, but these platforms can be expensive due to the cost of customised components, assembly, and maintenance, which limits the accessibility for many root researchers. To widen access to the rhizobox method—for example for preliminary screening of germplasm for root system architecture traits—we present a method to build a simple, low-cost rhizobox method using widely available materials, which should allow any research group to conduct root experiments and phenotype root system architecture in their own laboratories and greenhouses. Methods The detailed construction of 80 wooden rhizoboxes is described (each 40 cm width x 90 cm height x 6 cm depth; total cost 1,786 AUD, or 22 AUD or [$15 USD] per rhizobox). Using a panel of 20 spring wheat lines, including parental lines and derived intro-selection lines selected for divergent seedling root traits (seminal root angle and root biomass), genotypic variation in root biomass distribution were examined in the upper (0–30 cm), middle (30–60 cm) and lower sections (60–90 cm) of the rhizobox. At the conclusion of the experiment, rhizobox covers were removed and the exposed roots were imaged prior to destructive root washing. Root morphological traits were extracted from the images using RhizoVision Explorer (Seethepalli and York 2020). Results There were significant genotypic differences in total root biomass in the upper and middle sections of the rhizobox, but differences were not detected in the deepest section. Compared with the recurrent elite parent Borlaug100, some of the intro-selection lines showed greater biomass (or less), depending on the status of the root biomass QTL on chromosome 5B. Genotypes also differed in shoot biomass and tiller number. The donor lines for high and low root biomass showed corresponding differences in shoot biomass. Additional root parameters such as total root length and branching frequency were obtained through image analysis and genotypic effects were detected at different depths. Conclusions The rhizobox set up is easy-to-build-and-implement for phenotyping the root distribution of wheat. This will support root research and breeding efforts to identify and utilise sources of genetic variation for target root traits that are needed to develop future wheat cultivars with improved resource use efficiency and yield stability.