A major QTL on chromosome 7HS controls the response of barley seedling to salt stress in the Nure × Tremois population

Abstract

BackgroundSeedling establishment is a crucial and vulnerable stage in the crop life cycle which determines further plant growth. While many studies are available on salt tolerance at the vegetative stage, the mechanisms and genetic bases of salt tolerance during seedling establishment have been poorly investigated. Here, a novel and accurate phenotyping protocol was applied to characterize the response of seedlings to salt stress in two barley cultivars (Nure and Tremois) and their double-haploid population.ResultsThe combined phenotypic data and existing genetic map led to the identification of a new major QTL for root elongation under salt stress on chromosome 7HS, with the parent Nure carrying the favourable allele. Gene-based markers were developed from the rice syntenic genomic region to restrict the QTL interval to Bin2.1 of barley chromosome 7HS. Furthermore, doubled haploid lines with contrasting responses to salt stress revealed different root morphological responses to stress, with the susceptible genotypes exhibiting an overall reduction in root length and volume but an increase in root diameter and root hair density.ConclusionsSalt tolerance at the seedling stage was studied in barley through a comprehensive phenotyping protocol that allowed the detection of a new major QTL on chromosome 7HS.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-017-0545-z) contains supplementary material, which is available to authorized users.

Roles of seed components in the growth of barley seedlings under salt stress

“…In contrast, there was no significant contribution of genotype in RL-Control, but it increased gradually (from 11% to 22%) with increasing salinity up to 240 mM NaCl (Table S3). This indicated a strong genetic effect on root growth under moderate salt stress, as had already been demonstrated by the discovery of major QTLs in the OWB barley population (Witzel et al 2010) and NT barley population (Xue et al 2017). Hence, our results suggest that potential genetic influence on barley seedling traits is organ-(shoot vs. root) and condition-dependent.…”

“…A vertical seedling growth system, which has been described by Xue et al (2017), was used to germinate the collected seeds in 80, 160, 240, 320 and 400 mM sodium chloride (NaCl) solution, in parallel with control condition (no salt added). All "seeds" (referring in the wide sense to the barley grain spikelet) were incubated for 7 days in a growth chamber at 20 °C without light.…”

“…The resultant seedlings were photographed and graphically measured by Image J for root and shoot length (RL and SL, respectively), or coleoptile length in some treatments (regarded as SL). The obtained data were subjected to simulation with the Hill-3-parameter mathematical model (Joosen et al 2010) to draw dynamic curves of seedling length (y axis) against salinity (x axis) by Sigmaplot 12.0 (Systat Software, Inc., 2012, USA), wherein a is a limit value for the maximum seedling length (L max ), b controls the shape and steepness of the simulated curve, and c is the half-maximal activation level of the curve (Xue et al 2017). Coleoptiles rarely emerged in the 400 mM NaCl treatment, and seedlings without coleoptiles were recorded as having an SL value of 0 for further data modeling.…”

Genetic dissection of winter barley seedling response to salt and osmotic stress

“…Under experimental conditions aimed at studying seed germination or seedling growth, saline conditions and the osmotic component of drought stress are frequently simulated by sodium chloride (NaCl) and polyethylene glycol (PEG), respectively (Abdel-Ghani et al 2015;Shi et al 2015). To date, two major QTL controlling the response of barley seedlings to salt stress have been identified on chromosome 5HL in the Oregon Wolfe Barley (OWB) mapping population (Witzel et al 2010), and on chromosome 7HS in a Nure × Tremois (NT) population (Xue et al 2017). In contrast, only minor QTL were detected when seedlings of the OWB population were exposed to osmotic stress (Bálint et al 2008), and similar results were observed for other recombinant populations (Wójcik-Jagła et al 2013).…”

“…The mathematical Sigmoid model has also been applied to depict the dynamic response of seminal root growth in maize seedlings exposed to different salinities (Khan et al 2003). Similarly, the Hill function of the Sigmoid model was employed to simulate the response of barley seedlings to salt stress, and key parameters from the simulation curves (e.g., maximum seedling length (L max ), salt concentrations leading to 50% reduction in L max (Salt 50 )) were extracted for QTL mapping (Xue et al 2017). To date, these methodologies have been used separately for genetic analyses; however, their combination might increase the accuracy and efficiency of QTL discovery.…”