Mapping QTLs For Traits Associated With Drought Tolerance In Wheat (Triticum Aestivum L.) Seedlings

Object: Wheat is an important cereal crop in the world. However, drought stress strongly restricts wheat production in most arid and semi-arid areas. Genetic mechanism and function of quantitative trait loci (QTL) for the traits associated with drought tolerance were dissected in wheat seedlings using the theory and technology of molecular quantitative genetics. The aim is to provide the basis on genetic improvement and breeding for drought resistance by molecular marker assisted selection.Methods: The present study was carried with 150 doubled haploid lines (DHLs) of wheat derived from a cross between Hanxuan 10 and Lumai 14, two Chinese common cultivars. Under artificially simulative water-stress and re-water conditions, seedling traits related to drought tolerance, such as leaf relative water content (RWC), leaf relative conductance rate (RCR), root-shoot ratio (RSR), root dry weight (RDW), shoot dry weight(SDW), maximum root length (MRL) and water use efficiency (WUE) were measured and analyzed. Moreover, QTL for these traits were detected.Results:1. The relationship between the drought tolerance related traits and the mean membership function value was dissected. The result revealed their correlative relation.2. Path analysis showed that the interacted among the drought tolerance related traits by both direct effects and indirect effects .3. A total of 112 additive effect QTLs and 169 pairs of epistatic effect QTLs were detected under different water regimes.Conclusion:1. The contribution of the drought tolerance related traits to mean membership function value is RWC﹥RCR﹥RSR﹥MRL﹥RDW.2. The interaction effects among the drought tolerance related traits acted on mean membership fuction value not only by the direct effects, but also by their indirect effects. The interaction effects influenced the direct effects.3. The drought tolerance related traits were determined not only by both additive QTLs and epistatic QTLs. The epistatic effect of additive×additive mainly sourced genome A and B.4. QTLs expression patterns controlling the aim traits were varied under water stress and re-water conditions, but several important QTLs worked and expressed steadily were found.5.The chromosome 1B carried additive QTLs and epistatic effect of additive×additive QTLs controlling RWC, RCR and mean membership function value.6. Some important markers could be used in molecular marker assisted selection for drought torlerance. Marker WMC367 and WMC93 could be used for RWC selection. Xgwm153, Xgwm268, WMC44 and Xgwm259 were closely linkage with RCR. Marker WMC453.1, WMC18 and Xgwm644.2 for SDW, marker P3622-400, Xgdm86 and Xgdm88 for RDW, Marker Xgwm391, CWM539.2, Xgwm513 and P3454-470 for MRL, marker Xgwm165.2 and CWM48.1 for RSR, Xgwm194 for WUE, marker WMC367 and Xpsp3027 for mean membership function value were significative in the improvement of corresponding traits.