title: Soil coring at multiple field environments can directly quantify variation in deep root traits to select wheat genotypes for breeding.
abstract: We aim to incorporate deep root traits into future wheat varieties to increase access to stored soil water during grain development, which is twice as valuable for yield as water captured at younger stages. Most root phenotyping efforts have been indirect studies in the laboratory, at young plant stages, or using indirect shoot measures. Here, soil coring to 2 m depth was used across three field environments to directly phenotype deep root traits on grain development (depth, descent rate, density, length, and distribution). Shoot phenotypes at coring included canopy temperature depression, chlorophyll reflectance, and green leaf scoring, with developmental stage, biomass, and yield. Current varieties, and genotypes with breeding histories and plant architectures expected to promote deep roots, were used to maximize identification of variation due to genetics. Variation was observed for deep root traits (e.g. 111.4-178.5cm (60%) for depth; 0.09-0.22cm/°C day (144%) for descent rate) using soil coring in the field environments. There was significant variation for root traits between sites, and variation in the relative performance of genotypes between sites. However, genotypes were identified that performed consistently well or poorly at both sites. Furthermore, high-performing genotypes were statistically superior in root traits than low-performing genotypes or commercial varieties. There was a weak but significant negative correlation between green leaf score (-0.5), CTD (0.45), and rooting depth and a positive correlation for chlorophyll reflectance (0.32). Shoot phenotypes did not predict other root traits. This study suggests that field coring can directly identify variation in deep root traits to speed up selection of genotypes for breeding programmes.
authors: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia anton.wasson@csiro.au.
authors: A P
authors: AP
authors: Wasson
authors: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
authors: G J
authors: GJ
authors: Rebetzke
authors: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
authors: J A
authors: JA
authors: Kirkegaard
authors: Queensland Alliance for Agricultural and Food Innovation, University of Queensland, Leslie Research Centre, PO Box 2282, Toowoomba Queensland 4350, Australia.
authors: J
authors: J
authors: Christopher
authors: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
authors: R A
authors: RA
authors: Richards
authors: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
authors: M
authors: M
authors: Watt
mesh_terms: D001947:Breeding; D014644:Genetic Variation; D005838:Genotype; D010641:Phenotype; D018517:Plant Roots / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development; D012987:Soil; D014908:Triticum / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development
chemical_list: D012987:Soil
keywords: Deep roots; field phenotyping; physiological selection; root penetration rate; soil coring; wheat breeding.