Abstract
BackgroundPremature leaf senescence induced by external stress conditions, e.g. drought stress, is a main factor for yield losses in barley. Research in drought stress tolerance has become more important as due to climate change the number of drought periods will increase and tolerance to drought stress has become a goal of high interest in barley breeding. Therefore, the aim is to identify quantitative trait loci (QTL) involved in drought stress induced leaf senescence and drought stress tolerance in early developmental stages of barley (Hordeum vulgare L.) by applying genome wide association studies (GWAS) on a set of 156 winter barley genotypes.ResultsAfter a four weeks stress period (BBCH 33) leaf colour as an indicator of leaf senescence, electron transport rate at photosystem II, content of free proline, content of soluble sugars, osmolality and the aboveground biomass indicative for drought stress response were determined in the control and stress variant in greenhouse pot experiments. Significant phenotypic variation was observed for all traits analysed. Heritabilities ranged between 0.27 for osmolality and 0.61 for leaf colour in stress treatment and significant effects of genotype, treatment and genotype x treatment were estimated for most traits analysed. Based on these phenotypic data and 3,212 polymorphic single nucleotide polymorphisms (SNP) with a minor allele frequency >5 % derived from the Illumina 9 k iSelect SNP Chip, 181 QTL were detected for all traits analysed. Major QTLs for drought stress and leaf senescence were located on chromosome 5H and 2H. BlastX search for associated marker sequences revealed that respective SNPs are in some cases located in proteins related to drought stress or leaf senescence, e.g. nucleotide pyrophosphatase (AVP1) or serine/ threonin protein kinase (SAPK9).ConclusionsGWAS resulted in the identification of many QTLs involved in drought stress and leaf senescence of which two major QTLs for drought stress and leaf senescence were located on chromosome 5H and 2H. Results may be the basis to incorporate breeding for tolerance to drought stress or leaf senescence in barley breeding via marker based selection procedures.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0524-3) contains supplementary material, which is available to authorized users.
Highlights
Premature leaf senescence induced by external stress conditions, e.g. drought stress, is a main factor for yield losses in barley
An exception are some genotypes of the Spanish barley core collection (SBCC) (SBCC 3, 12, 14, 76, 80, 138 and 140) showing no decrease in Soil Plant Analysis Development (SPAD) and electron transport rate at photosystem II (ETR) or even an increase, represented by negative values across treatments (DSI)
By genome wide association studies (GWAS) marker trait associations for above ground biomass and physiological traits involved in drought stress tolerance and leaf senescence in early developmental stages of barley were detected
Summary
Premature leaf senescence induced by external stress conditions, e.g. drought stress, is a main factor for yield losses in barley. The aim is to identify quantitative trait loci (QTL) involved in drought stress induced leaf senescence and drought stress tolerance in early developmental stages of barley (Hordeum vulgare L.) by applying genome wide association studies (GWAS) on a set of 156 winter barley genotypes. Abscisic acid (ABA) is a key phytohormone involved in adaption to environmental stresses and regulation of plant development It promotes the closure of stomata under drought stress conditions initiated by a loss of turgor [13]. It increases the hydraulic conductivity of water, promotes chlorophyll breakdown and leads to leaf senescence [14]. Biomass production [25], yield [26], photosynthesis rate [27], as well as the content of free proline [28], total content of soluble sugars [29], or osmolality [30] are parameters which are affected by drought stress in barley
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