Dadshani, Said Abdul Wali: Genetic and physiological characterization of traits related to salinity tolerance in an advanced backcross population of wheat. - Bonn, 2018. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
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author = {{Said Abdul Wali Dadshani}},
title = {Genetic and physiological characterization of traits related to salinity tolerance in an advanced backcross population of wheat},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2018,
month = mar,

note = {In large areas of the world wheat production is highly affected by soil salinity. Increasing the genetic variability of currently used wheat varieties is an efficient approach to overcome production losses and prevent food insecurity. Synthetic hexaploid wheat is widely regarded as donor of favorable exotic alleles with respect to tolerance against biotic and abiotic stress factors such as salinity stress. The objective of the present study was to identify genomic regions, which contribute to salinity tolerance at various growth stages in wheat. Therefore, the 151 advanced backcross lines (AB-lines) of the winter wheat population “Z86” (BC2F3:7), containing introgressions of the synthetic hexaploid wheat Syn86L in the background of the German elite cultivar Zentos, were employed in this study. Salt stress experiments were conducted at germination and seedling stage as well as under field conditions with natural salinization in Uzbekistan in three consecutive years. At various growth stages, the AB-lines of the Z86 population and their parents were differently affected by salt stress. At the same molar concentration of salts, the impact of sodium sulfate (Na2SO4) on plants growth was higher than of sodium chloride (NaCl). Notably, for most studied parameters the recurrent elite parent Zentos was performing better than the synthetic parent Syn86, the donor of exotic alleles. In respect to root and shoot length Syn86 surpassed the elite cultivar.
In this study, several non-destructive sensor technologies were used which allow accurate and continuous monitoring of morpho-physiological parameters of plants exposed to salinity stress. These data present the first report of a dual-mode microwave resonator which was allowing accurate estimation of water content as well as the ionic conductivity in leaves of mono- and dicotyledonous plants. Additionally, measurement of the photosynthetic rate of plants exposed to salt shock revealed highly significant genotype by treatment interaction effect 20 minutes after initiation of salt stress, where Zentos was performing better than Syn86.
In order to detect genomic regions associated with the measured traits under salinity stress the Z86 population was genotyped using the iSelect 90K chip. After data cleaning 11,050 polymorphic SNP marker remained which were applied for quantitative trait loci analysis (QTL) for the 48 studied traits. Using SAS 9.4 the multi-locus approach incorporated in the hierarchical QTL model was able to reduce the number of false-positive putative QTL and hence endorsed the power of detected true QTL. In summary, 116 QTL main effects (including QTL with epistatic effects) and 165 QTL for marker by treatment interaction (including QTL with epistatic by treatment interaction) were detected. One of the major QTL showing pleiotropic effects, among them on shoot dry weight under salinity stress, was found on the short arm of chromosome 7D at 29.97 cM. In-silico analysis of the QTL chromosome region revealed a gene coding for TaGSTu3, an enzyme belonging to the tau-class of the glutathione S-transferase family (GST). GSTs are well known for their role in detoxification of reactive oxygen species (ROS) in plants, which is highly increased under salinity stress. Gene expression analysis at three time-points during the seedling stage (10, 16 and 30 days after salt application) revealed higher expression of TaGSTu3 in Zentos under salinity stress and decreased expression in the comparing parent Syn86. This is the first report of atau-class GST found to contribute significantly to salinity tolerance in wheat.
The present study successfully identified QTL from elite cultivar Zentos as well as from the donor germplasm Syn86.The detected favorable alleles introgressed in the AB-lines of the Z86 population can be directly employed in breeding programs via marker-assisted selection for efficiently breeding cultivars with improved salinity tolerance and desired agronomic traits.},

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