Abstract
BackgroundMore 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 microelectrode ion flux estimation (MIFE) method, we have also found a major QTL conferring ROS control of ion flux in roots 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.ResultsIn 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 using barley as a check species. In viability staining experiments, a dose-dependent H2O2-triggered loss of root cell viability was observed, with salt sensitive varieties showing significantly more damage to root cells. In the root growth assays, relative root length (RRL) was measured in plants grown in paper rolls under different H2O2 concentrations. The biggest difference in RRL between contrasting varieties was observed for 1 mM H2O2 treatment. Under these conditions, a significant negative correlation in the reduction in RRL and the overall salinity tolerance is reported.ConclusionsThese 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 in barley (and potentially other species).
Highlights
More than 20% of the world’s agricultural land is affected by salinity, resulting in multibillion-dollar penalties and jeopardising food security
When roots were treated with H2O2 for 3 days, the red fluorescence signal can be readily observed from H2O2 treatments above 3 mM (Fig. 1b)
Mild root damage was observed upon 1 day H2O2 treatment, and there was no significant difference between elongation zone and mature zone for any concentration used (Fig. 2a)
Summary
More than 20% of the world’s agricultural land is affected by salinity, resulting in multibillion-dollar penalties and jeopardising food security. Using the microelectrode ion flux estimation (MIFE) method, we have found a major QTL conferring ROS control of ion flux in roots 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. One of constraints imposed by salinity stress on plants is an excessive production and accumulation of reactive oxygen species (ROS), causing oxidative stress. This results in a major perturbation to cellular ionic homeostasis [8] and, in extreme cases, to a severe damage to plant lipids, DNA, proteins, pigments and enzymes [9, 10]. Given the fact that AO profiles show strong time- and tissue(and even organelle-specific) dependence and in 50%
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