Root responses of triticale and soybean to soil compaction in the field are reproducible under controlled conditions

Soil compaction includes a set of underlying stresses that limit root growth such as increased impedance and limited oxygen availability. The aims of the present study were to (i) find acclimations of triticale (x Triticosecale) and soybean (Glycine max L.) roots to compacted soils in the field; (ii) reproduce these under controlled conditions; and (iii) associate these responses with soil physical properties. To this end, plants were grown at two different soil bulk densities in the field and under controlled conditions representing mature root systems and the seedling stage respectively. Diameters, lateral branching densities, the cortical proportion within the total root cross-section and the occurrence of cortical aerenchyma of main roots were quantified. Soil compaction caused decreasing root branching and increasing cortical proportions in both crops and environments. In triticale, root diameters and the occurrence of aerenchyma increased in response to compaction in the field and under controlled conditions. In soybean, these acclimations occurred at an initial developmental stage but due to radial root growth not in mature roots. These results showed that responses of root systems to compacted soils in the field are, to a large extent, reproducible under controlled conditions, enabling increased throughput, phenotyping-based breeding programs in the future. Furthermore, the occurrence of aerenchyma clearly indicated the important role of limited oxygen availability in compacted soils on root growth.