Highlight (max 30 words) 5A field phenotyping approach was developed for wheat to evaluate root phenes for the crown, 6 main shoot, and tillers of a mapping population, revealing substantial heritable variation. field and measuring root properties such as numbers, angles, densities and lengths. We report 1 3 a new shovelomics method that images the whole wheat root crown, then partitions it into the 1 4 main shoot and tillers for more intensive phenotyping. Root crowns were phenotyped using doubled-haploid lines. For the whole root crown, the main shoot, and tillers, root phenesincluding nodal root number, growth angle, length, and diameter were measured. Substantial latent constructs that imply pleiotropic genetic control of several related root phenes. 0Correlational analysis revealed that nodal root number and growth angle correlate among the 2 1 whole crown, main shoot, and tillers, indicating shared genetic control among those organs. 2We conclude that this phenomics approach will be useful for breeding ideotype root systems 2 3 in tillering species. 4Key words: Rooting, abiotic stress, Triticum aestivum L., fertilizer, water, nitrogen, soil, 2 5 resource acquisitionThe global population is expected to increase to nine billion people by 2050 which 2 8necessitates an increase in global food production of at least 60%, but likely as much as 2 9100% due to increased livestock production (Grafton et al., 2015). Wheat is a staple crop in 3 0 many countries, grown on 220 million hectares with a global yield of 729 million tonnes 3 1

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Optimization of root system architecture represents an important goal in wheat breeding. Adopting new field methods for root phenotyping is key to delivering this goal. A novel ‘shovelomics’ method was applied for phenotyping root crown traits to characterize the Savannah x Rialto doubled-haploid (DH) population in two field experiments under irrigated and rain-fed conditions. Trait validation was carried out through soil coring on a subset of 14 DH lines and the two parents. We observed that drought reduced grain yield per plant by 21.0%. Under rain-fed conditions, nodal root angle and roots shoot-1 were positively associated with root length density (RLD) at 40-60 cm depth; RLD was also positively correlated with grain yield. Nodal root angle and roots shoot-1 were also positively associated with canopy stay green and grain yield under rain-fed conditions. We conclude that shovelomics is a valuable technique for quantifying genetic variation in nodal root traits in wheat, revealing nodal root angle and root number per shoot provide useful selection criteria in breeding programs aimed at improving drought tolerance in wheat.HighlightNodal root angle and number shoot-1 measured using ‘shovelomics’ were positively associated with root density at depth and yield under drought in a Savanah x Rialto wheat DH population.