| Drought is one of the abiotic stresses affecting wheat production in China. Drought tolerance is acomplex quantitative trait. However, the rapid development of molecular quantitative genetics hasprovided an effective approach to map QTLs and to dissect genetic factors for complex quantitativetraits associated with drought tolerance.In this study, two sets of wheat introgression lines (ILs) generated from repeated backcrosses[(Lumai14×Jinmai47)×Lumai14] BC3F4and [(Lumai14×Chang6878)×Lumai14] BC3F4wereused as the plant materials. The physiological traits associated with drought tolerance (canopytemperature, canopy temperature depression, chlorophyll content and chlorophyll fluorescence kineticsparameters) were identified under two water regimes, drought stress (DS) and well-watered (WW). QTLfor these traits were mapped to reveal the genetic basis of inheritance and QTL expression pattern. Theresearch results were as follows:1. Most of the mean values of traits showed substantial transgressive segregation in the ILs. Theaverages of IL traits tended to be closer to the recurrent parent Lumai14. Canopy temperature andchlorophyll fluorescence kinetics parameters were more stable in Jinmai47and Chang6878than inLumai14. The introgression lines showed a similar tendency, but were less stable than Jinmai47. Thedifferential performance of ILs under the two water regimes shows drought stress influenced wheat inthe growing period.2. The genetic basis of traits associted with drought tolerance is complicated in wheat and QTL canhave both additive and epistatic effects. Some QTL interacted with other QTL to influence the trait.Therefore, marker-assisted selection breeding needs to consider the complex genetic relationship amongthe QTL.3. Through two sets of backcross introgression lines it was found that QTL for CT (canopytemperature) and CTD (canopy temperature depression) are widely distributed on the chromosomes.The QTL which control CT and CTD shared the same loci or adjacent sites on chromosomes. In ILswith Jinmai47as the donor parent, markers such as wPt-2087on2A, wPt-0697on2B, wPt-5586on2D,Xgwm155and wPt-4859on3A, Xgwm3on3D, wPt-6039and wPt-1241on6B and rPt-398831on7Bcontrol CT and CTD at the same site. Similarly, in ILs with Chang6878as the donor parent, Xgwm513on chromosome4B, barc56on5A and wPt-2407on7B controlled both characters. Therefore, QTLwhich control water-related traits may have a similar genetic region in wheat.4. In the two sets of ILs, QTL controling ChlC (chlorophyll content) were distributed unevenly onchromosomes. More QTL were distributed on chomosomes2B,3B and4A (total of12QTL). Some ofthese QTL were detected repeatedly under different growth stages or water regimes indicating they mayplay a role in controlling wheat stay-green traits. Some QTL were also concentrated adjacent to eachother, such as the wPt-744576~wPt-744088on2B and wPt-5489~wPt-3435on4A. These QTL hot-spot regions were significant in predicting the genetic map locations of wheat genes associated withchlorophyll content and the genetic basis of the stay-green traits.5. QTL of PCFK (parameters of chlorophyll fluorescence kinetics) were concentrated on a smallnumber of chromosomes. In ILs with Jinmai47as the donor parent, QTL of PCFK mainly distributedon1B,3A and7B, while in ILs with Chang6878as the donor parent, QTL were found on1B,2B,6Aand6B. In addition, the study found that54.12%of the additive QTL controling PCFK contribution rateof phenotypic variation explained is greater than10%of the phenotypic variation, while all the epistaticQTL contributed more than10%. Clearly epistatic effects are an important part of PCFK and play animportant role in the genetic basis of PCFK.The present research identified QTL linked to physiological traits associated with drought tolerancein wheat. The research results provided a genetic basis and techniques for improving drought tolerancein wheat, and some stably expressed QTL maybe important for functional studies of related genes andmap based cloning. |
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