Developing a High-Throughput Phenotyping Method for Oxidative Stress Tolerance in Cereal Roots

More than 20% of the world’s agricultural land is affected by salinity resulting in multibillion-dollar penalties and jeopardising food security. While the recent progress in molecular technologies has significantly advanced plant breeding for salinity stress tolerance, accurate plant phenotyping remains a bottleneck of many breeding programs. We have recently shown the existence of a strong causal link between salinity and oxidative stress tolerance in cereals (wheat and barley). Using the MIFE method, we have found a major QTL conferring ROS control of ion flux in roots located on the 7H chromosome that coincided with the major QTL for the overall salinity stress tolerance. These findings open new (previously unexplored) prospects of improving salinity tolerance by pyramiding this trait alongside with other (traditional) mechanisms. In this work, two high-throughput phenotyping methods - viability assay and root growth assay - were tested and assessed as a viable alternative to the (technically complicated) MIFE method. In viability staining experiments, a dose-dependent H₂O₂-triggered loss of root cell viability was observed, with salt sensitive varieties showing significantly more root cell damage. In the root growth assays, root elongation rate (RER) was measured in plants grown hydroponically on H₂O₂ gradient. The biggest difference in RER between contrasting varieties was observed for 1 mM H₂O₂ treatment. Under these conditions, a significant negative correlation between RER and the overall salinity tolerance was reported. These findings offer plant breeders a convenient high throughput method to screen germplasm for oxidative stress tolerance, targeting root-based genes regulating ion homeostasis and thus conferring salinity stress tolerance.