Genotype by environment (GxE) interactions for root depth of wheat: Associations and implications

A significant proportion of arable land is susceptible to subsoil compaction or soil physical constraint, which limits root access to water and nutrients at depth. This paper reviews recent research on root traits for hardpan penetration and water extraction. The ability of roots to penetrate a compacted soil layer was simulated experimentally by growing plants in soil columns containing a thin paraffin wax-petroleum jelly layer. The objective was to assess temporal variation of root growth of Australian wheat cultivars in terms of their penetration ability with or without a thin wax layer and/or contrasting water regimes, and relate this to performance on contrasting soils in the field. GxE for root depth in the field was examined, and its association with various soil parameters and other root and shoot traits. Cranbrook/Halberd doubled-haploid lines (DHL) were phenotyped for hardpan penetration in the laboratory, and the root depth of contrasting DHLs was assessed in different soils in the field. Quantitative trait loci (QTL) for hardpan penetration were identified. This research established root penetration may be screened using the wax layer system, and that root penetration benefits root depth in the field. Cultivars with enhanced root penetration should be advantageous in many situations.