Genotypic Variation in Root Angle of Wheat (Triticum aestivum L.) May Have Implications for Establishment in Surface Crusted Sodic Soil

The growth angle between seminal roots is an important component of root traits, and the efficiency of water acquisition by certain crops under constrained soils has previously been found to be related to root angle. In this study, the surface crusting of sodic soils is a major problem in the semi-arid tropics which can result in reduced seedling emergence and grain yield. The identification of root trait(s) responsible for tolerance to sodic soils and soil crusting may improve selection of wheat (Triticum aestivum) genotypes adaptation in such soils. The aim of this study was to examine the extent of genotypic variability for the root growth angle across 16 current Australian wheat genotypes, and to compare this to their performance in surface crusted sodic soils.

Root growth angles were measured for 16 wheat genotypes grown at a constant temperature (17°C) in a growth chamber in one of two soils: (i) sodic (10% exchangeable Na) or (ii) control (0% exchangeable Na). A separate experiment was used to study the emergence of these 16 genotypes in the presence of artificially created surface crust using sodic dispersive soil in the glasshouse.

Across the 16 genotypes, no significant variation was observed in the growth angle of the seminal roots between sodic and control soils. However, the growth angle of seminal roots differed significantly between genotypes, with values ranging from 80° to 126°. Additionally, in the surface crust experiment, significant differences (P<0.0001) was observed between the emergence of wheat genotypes, ranging from 0 to 95 %. A negative correlation (R²=0.48) was observed between seedling root angle and emergence in the crusted sodic crusted soil. The results suggest that the selection of wheat genotypes with narrower root angles may offer a strategy to improve seedling emergence in crusted sodic soils and to improve crop establishment and yields.