Yield progress in wheat is slowing in major production regions. Seminal root angle and root number of seedlings are considered as proxy traits for early selection of deep, rooting systems, which can allow increased water extraction in deep, drying soils during the grain filling period. Recently, a low-cost, high-throughput phenotyping method has been proposed to screen high numbers of lines (Richard et al. 2015. Plant Methods 11:13). As soil temperature varies substantially in field conditions, we tested the robustness of this method under a large range of temperatures. Seeds of 48 genotypes contrasting for seminal root angle and root number were grown in pots at constant temperatures ranging from 11 to 29 °C with non-limiting nutrient and moisture. Using a combination of image analysis and destructive measurements, seminal root angle, root number, root length and shoot length were measured. Genotype x environment interactions were observed for all the studied traits, particularly for root number. High genetic correlations between the tested temperatures were found for root angle, highlighting that genotype screening for this trait may be performed at different temperatures with little impact on genotype ranking. Thus the phenotyping method was effective across temperatures and, therefore, could be useful for screening in non-controlled environments, making it highly attractive for breeding purposes.
Keywords: root architecture; high-throughput phenotyping; image analysis; crop improvement; Triticum aestivum.