Abstract
Seedling establishment is a vulnerable stage in the crop life cycle which can be affected by different abiotic stresses. Drought and salinity are major environmental constraints worldwide, but few studies have genetically compared these two stresses on the same genetic material. In this study, the dynamic response of barley seedling growth to different levels of salt stress and PEG6000-mediated osmotic stress was evaluated in a European winter barley cultivar collection, in parallel with non-stress conditions. Salt and osmotic stress experiments produced different root-response curves. A final set of 56 phenotypic traits was subjected to genome-wide association mapping with 4885 gene-based SNP markers: 28 quantitative trait loci (QTL) were identified; 10 loci were found to be involved in saline conditions, whereas 20 loci were detected under osmotic stress. Four loci on chromosomes 1H, 5H and 6H were detected under more than one growth condition. One co-localized QTL was involved in both root and shoot growth only under salt stress. A set of potential candidate genes with putative pleiotropic effects on seedling growth under different conditions is proposed, based on their physical proximity to the QTL peak markers. To conclude, we found that a QTL controlling seedling growth under one abiotic stress can respond to another stress. QTL promoting faster growth under non-stress conditions were also identified under salt and/or osmotic stresses. These loci might be exploited in breeding programs to overcome environmental stresses at the initial seedling stage.
Highlights
Drought and salinity are major abiotic stresses limiting crop productivity (Rizwan et al 2015)
The dynamic responses of barley seedlings to various salt and osmotic stresses are reported in Fig. 1A and B, respectively, for the whole winter barley collection, with representative curves calculated from the mean values of both seminal root length (RL) and shoot length (SL)
Fewer quantitative trait loci (QTL) were mapped from salt-stressed seedlings in comparison with osmotically stressed seedlings, and most of them were independent of previously reported loci
Summary
Drought and salinity are major abiotic stresses limiting crop productivity (Rizwan et al 2015). Climate change is expected to significantly impact temperature and precipitation profiles, increasing the incidence and severity of environmental stresses (Mondini and Pagnotta 2015) For this reason, drought stress is often combined with salinity in many of the world’s arid and semiarid regions, where irrigation water is prone to. Agricultural drought is defined as a period with decreased soil moisture that leads to crop failure without any reference to surface water resources (Mishra and Singh 2010). It is quantified as a reduction in water potential (ψw) and classified as an osmotic threat (Mondini and Pagnotta 2015). Most reports have focused on testing these genes’ functions rather than on their exploitation in breeding programs for stress tolerance (Yun et al 2012)
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