Curtis and The Three Beres: investigating early seedling root-soil interface traits in modern and landrace barley genotypes

It is not known whether modern crop breeding lost valuable root-soil interface traits present in landraces beneficial to soil-carbon storage, nutrient and water use efficiency, and remediation of degraded soil structure. Landraces are defined as crop genotypes which are locally adapted to environmental and management conditions. These ancient cultivars may provide a valuable source of genetic diversity and agronomic traits which can be bred into higher-yielding modern cultivars to improve yield stability under lower input or stressed conditions. Within the Highlands of Scotland, the “Bere” barley landrace is a multipurpose crop with cultural importance, early maturity, and evidence of advantageous root-soil adaptations to micronutrient deficiency.

In this study, three Bere genotypes and the modern barley cultivar KWS Curtis were grown under highly controlled conditions to evaluate genotype differences at the root-soil interface. In a seedling assay, plants were grown in growth cabinets for 4 days in sandy loam soil packed to a defined bulk density and water contents. This rapid and low-cost methodology demonstrated a high level of reproducibility in rhizosheath size and root traits, with no significant difference between root hair length and root system length between experiments. Additionally, two of the three Bere landraces were found to have a significantly larger rhizosheath (P=0.001) than the modern cultivar KWS Curtis at the earliest stage of seedling growth (GS 10, first leaf emergence): 39% and 19% increase for “Unst” and “Challoner” vs KWS Curtis, respectively. Conversely, KWS Curtis had much greater (P<0.001) above ground biomass than the three Bere genotypes with “Unst” having a 93% lower above ground biomass than KWS Curtis. This suggests that the modern cultivar favoured above-ground allocation of resources over root exudation in early seedling growth.

This study serves as a platform to investigate fine-scale rhizosphere characteristics and spatial distribution of soil modification through root hair-exudate-microbial interactions. The screening approach provides a rapid assay to select genotypes with favourable traits from seedling characteristics, which will be verified with more mature plants in future research.