Precrop-treated soil influences wheat (Triticum aestivum L.) root system architecture and its response to drought

Abstract

Aims: Root system architecture (RSA) plays an important role in the plant's ability to sustain yield under abiotic stresses such as drought. Preceding crops (precrops) can affect the yield of the proceeding crop, partially by affecting the RSA. This experiment aims to explore the interactions between precrop identity, crop genotype and drought at early growth stages.

Methods: Rhizotrons, sized 60 × 80 × 3.5 cm, were used to assess the early root growth of two winter wheat (Triticum aestivum L.) genotypes, using precrop-treated soil around the seedlings and differing water regimes. The rhizotrons were automatically imaged 3 times a week to track root development.

Results: Precrop-treated soil affected the RSA and changes caused by the reduced water treatment (RWT) were different depending on the precrop. Largest of these was the 36% reduction in root depth after wheat, but 44% after OSR. This indicates that effects caused by the precrop can be simulated, at least partially, by transferring precrop-treated soils to controlled environments. The genotypes had differential RSA and reacted differently to the RWT, with Julius maintaining an 8.8-13.1% deeper root system compared to Brons in the RWT. In addition, the combined environmental treatment affected the genotypes differently.

Conclusion: Our results could help explain discrepancies found from using precrops to enhance yield as they indicate differences in the preceding crop effect when experiencing drought stress. Further, these differences are affected by genotypic interactions, which can be used to select and adapt crop genotypes for specific crop rotations, depending on the year. Additionally, we have shown a viable method of stimulating a partial precrop effect at the seedling stage in a controlled greenhouse setting using field soil around the germinated seed.

Keywords: G×E interaction; Triticum aestivum; precrop effect; rhizotron; root system architecture; water stress.

Figure 1

Spread of nitrogen data from the combined shoot and root material of two replicates. Comparing: (A) the water treatment, control (magenta) or reduced (RWT; orange), effect on the nitrogen concentration, and (B) the total treatment effect on the total plant nitrogen, separated by genotype, with the combined treatment including; precrop soil treatments of Peat compost (green), soil taken after OSR growth (yellow), or soil taken after wheat growth (purple); and the control (dark) or Reduced (RWT; light) water treatments. Significance is based on the Tukey pairwise comparisons adjusted p-value, with * = p>0.05, ** = p>0.01, and *** = p>0.001.

Figure 2

Average total root length (A), root system width (B), and convex hull area (C) at each time point, separated by the type of medium used as the precrop soil section; peat compost (green), soil taken after OSR growth (yellow), or soil taken after wheat growth (purple). The dashed line (B) indicates the width of the precrop soil addition where appropriate.

Figure 3

Progression of visible root traits over the different imaging dates of the rhizotron, for axial root length (A), lateral root length (B), root system depth (C), root system width (D), and convex hull area (E). Data is separated by genotype (G – genotype) and divided by environment (E – precrop soil and water). Environmental divides are by colour for precrop soil – Peat compost (green), soil taken after OSR growth (yellow), or soil taken after wheat growth (purple) – with the dashed line (B, C) indicating the depth and width of the precrop soil addition. Shape and shade denoting water treatment – control as circles and darker shade, reduced (RWT) as triangles and in lighter colour shades.

Figure 4

The total depth of the visible root system over the different imaging dates of the rhizotron. Divided by genotype (Brons in yellow, Julius in blue), and by water treatment (control as circles, reduced (RWT) as triangles). The dashed line indicates the depth of the precrop soil addition where appropriate.

Figure 5

Distribution of length of axial (A, C) and lateral (B, D) roots, on the last measurement day (24), within the different areas of the box, split into either 11 sections horizontally (A, B) or 14 sections vertically (C, D), with the average distance from centre or depth (respectively) taken for each box. Data is divided by the type of medium used as the precrop soil section; Peat compost (green), soil taken after OSR growth (yellow), or soil taken after wheat growth (purple). The dashed black lines represent the distance from the centre, or depth (respectively) that the precrop soil section ended.