Clear effects on root system architecture of winter wheat cultivars (Triticum aestivum L.) from cultivation environment and practices

Abstract

Roots play a pivotal role in the adaption of a plant to its environment, with different root traits adapting the plant to different stresses. The environment affects the Root System Architecture (RSA), but the genetic factors determine to what extent, and whether stress brought about by extreme environmental conditions is detrimental to a specific crop. This study aimed to identify differences in winter wheat RSA caused by cultivation region and practice, in the form of preceding crop (precrop), and to identify if modern cultivars used in Sweden differ in their reaction to these environments. This was undertaken using high-throughput phenotyping to assess the RSA. Clear differences in the RSA were observed between the Swedish cultivation regions, precrop treatments, and interaction of these conditions with each other and the genetics. Julius showed a large difference between cultivars, with 9.3-17.1% fewer and 12-20% narrower seminal roots. Standardized yield decreased when grown after wheat, 23% less compared to oilseed rape (OSR), and when grown in the Southern region, 14% less than the Central region. Additionally, correlations were shown between the root number, angle, and grain yield, with different root types being correlated depending on the precrop. Cultivars on the Swedish market show differences that can be adapted to the region-precrop combinations. The differences in precrop effect on RSA between regions show global implications and a need for further assessment. Correlations between RSA and yield, based on root-type × precrop, indicate different needs of the RSA depending on the management practices and show the potential for improving crop yield through targeting genotypic and environmental conditions in a holistic manner. Understanding this RSA variance, and the mechanisms of conditional response, will allow targeted cultivar breeding for specific environments, increasing plant health and food security.

Keywords: Triticum aestivum; Precrop effect; Root growth; Root system architecture; Wheat yield.

Figure 1

Differences in nodal root number (A) and angle (B), and seminal root number (C) and angle (D) between the two growing regions of Sweden–Svalöv in Skåne (green) and Bjertorp in Västergötland (purple). The significance is based on the estimated marginal means from the emmeans package in ‘R’; denotations are ‘*’ for p < 0.05, ‘***’ for p < 0.0001, and ‘NS’ for no significance.

Figure 2

Differences in nodal root number (A), nodal root angle (B), and seminal root number (C), between the two different preceding crops–OSR (yellow) and wheat (blue). The nodal root data (A,B) is further split between the two different growing regions in Central (Bjertorp) and Southern Sweden (Svalöv) each with two field sites for the different precrops. The nodal root number (A) is further faceted by the sampling period. The significant difference is based on the estimated marginal means from the emmeans package in ‘R’, and is only within the same sampling period for nodal root number (A). The denotations are ‘*’ for p < 0.05, ‘*’ for p < 0.01, and ‘***’ for p < 0.0001. Faceted data for seminal root number and angle is displayed in Supplementary Fig. 7.

Figure 3

Differences in seminal root number (A) and angle (B), between different cultivars (coloured) of wheat plants field-grown in two growing regions in Central (Bjertorp) and Southern Sweden (Svalöv)—the data is divided by these regions for seminal root angle (B). The significance is based on the estimated marginal means from the emmeans package in ‘R’; cultivars without a matching letter, are significantly different (p < 0.05).

Figure 4

Differences in nodal root number (A) and angle (B), between different cultivars of wheat plants field-grown in two growing regions in Central and Southern Sweden. The data is divided by sampling period, and coloured depending on precrop–OSR (yellow) or wheat (blue). Pairwise comparisons are noted in Supplementary Table 1.

Figure 5

Pearson’s correlations of yield values, standardized to account for differing moisture levels, with seminal (A,C) and nodal (B,D) root numbers (A,B) and angles (C,D) of wheat plants field-grown in two growing regions in Central and Southern Sweden. Regression lines are fitted based on the precrop of either OSR (yellow) or wheat (blue), with a facet grid dividing the root data by collection during the elongation phase (2021) and flowering phase (2020 & 2021).

Figure 6

Principle component analysis of shoot characteristic, root system architecture, and yield values, standardized to account for differing moisture levels of winter wheat plants field-grown in two growing regions in Central and Southern Sweden. The values are standardized to the mean of the entire Elongation (A,C) or Flowering (B,D) datasets and then split based on the precrop of either OSR (A,B; yellow) or wheat (C,D; blue).