| Drought stress is a major environment constraint greatly impacting wheat (Triticum aestivum L.) production in many wheat planted area that rely on rainfed of the world. The resistance or tolerance to abiotic stress were essentially subjected to complex quantitative genetics regulated by minor-effect polygenes, which were easily affected by different environments. The development of molecular quantitative genetics for studying the genetic basis of quantitative traits provides the possibility. Therefore, it is very important to improve the efficiency of drought resistance breeding plays an important role that to map QTLs and to dissect genetic factors for complex quantitative traits, and to enhance awareness of these traits.Doubled haploid lines (DHLs) (Hanxuan 10×Lumai 14) (150 lines) were selected as experiment materials in this study, (1) Under rainfed (drought stress) and well-watered conditions, important agronomic traits including morphological traits (leaf length, leaf width, leaf angle of the top three leaves, first internode length below spike (ILS) and plant height (PH) ), physiological traits (chlorophyll content, ChlC and rate of excised-leaf water loss,RWL), growth period (heading date (HD) and flowering date (FD) and yield-related traits (spike length (SL), spikelet number (SN), infertile spikelet number (ISN), grain number per spike (GNS), grain weight per spike (GWS), grain length (GL), grain width (GW) and thousand grain weight (TGW)) were investigated in two years; (2) coleoptile length (CL), coleoptile weight (CW), seedling height (SH) under different sowing depth, PEG (polyethylene glycol) treatment and water control conditions and seedling biomass (SB) (under drought stress and well-watered) simultaneously investigaed. QTL (quantitative trait loci) mapping and QTLs×water environment interactions (QEIs) were analyzed for these target traits, and explored environmental conditions that had impacted on these target traits, as well as relatonship between target traits. Main research results were as follows:1. Coleoptile length, weight and seedling height increased with the increase of sowing depth. Plant height of control was significantly higher than PEG treatment, but coleoptile length and weight were converse. Drought stress inhibited the seedling growth, resulting in the reduced of seedling biomass, leaf size and plant height, accelerated plant senescence, which eventually led to the reduction of production.2. Many important morphological, physiological and agronomic traits of wheat showed significantly sensitive to drought stress, which were characters of complex quantitative traits and easily affected by different environments. The genetic factors regulating these traits consisted of additive QTLs, epistatic QTLs, additive QEIs (A-QEIs) and epistatic QEIs (E-QEIs) effects.3. Major and minor QTLs for all target traits showed disequilibrium distribution among different chromosomes and even different intervals in the same chromosome. These QTLs assembled in some specific interval formed the hot-spot region for regulating inheritances of corresponding traits; some stable expression QTLs were detected in different years.4. A total of 13 additive and 24 pairs of epistatic QTLs were detected for CL, CW, SH and SB, which distributed on 18 (except for 1A, 1D and 6D) chromosomes. Co-located QTLs for CL, CW and SH were detected in the interval Xgwm165.2～Xgwm192 on 4D; major QTL loci for SH, SB and CL, CW were found in P3465-460～P3526-130 on 6A and Xpsp3033～Xgwm297 on 7B, respectively; 7 additive QTL and 10 pairs of epistatic QTL were identified significant QEIs with environment.5. A total of 50 additive and 22 epistatic QTLs were detected for leaf length, leaf width, and leaf angle of the top three leaves, which distributed on 20 (except for 6D) chromosomes. Xgwm630～WMC223 on 2B, WMC453.1～WMC18 on 2D, P3156-1851～P5138-100 on 3B, Xgwm304～P2470-280, Xgwm595～WMC410, WMC410～WMC74 and Xgwm291～Xgwm410 on 5A and Xpsp3033～Xgwm297 on 7B were common regions shared by multi-trait QTLs. QFll.cgb-5A-1, QSll.cgb-5A-1, QTll.cgb-5A-1, QFlw.cgb-2B, QFlw.cgb-3B-2, QSlw.cgb-3B, QFla.cgb-1B, QFla.cgb-5A-1, QSla.cgb-5A-1 and QTla.cgb-3B were detected in both two years. One additive QTL for second leaf angle and one pair of epistatic QTL for second leaf length were found significant QEIs with rainfed environment.6. QTLs for ChlC and RWL were distributed on 17 (except for 1A, 3D, 4D and 6D) chromosomes; QTL for ChlC in different development stages were detected in the interval P2470-280～Xgwm on 5A, QTL for different excised duration in heading date were detected in WMC436～Xgwm44 on 7D. Total of 3 additive QTL and 3 pairs of epistatic QTL were found significant QEIs with water environment.7. A total of 14 additive and 5 pairs of epistatic QTLs were detected for HD and FD which distributed on 1B, 1D, 2D, 3A, 3B, 4D, 6B, 7A, 7B and 7D chromosomes. Q.Hd.cgb-1D, Q.Fd.cgb-1D-1 and Q.Hd.cgb-3A, Q.Fd.cgb-3A were simultaneously located on the interval WMC432～WMC222 on 1D and Xgwm391～P8422-170 on 3A; QHd.cgb-7B-2 and Q.Fd.cgb-1B-1 were found significant A-QEIs with rainfed environment.8. A total of 62 additive and 29 pairs of epistatic QTLs for 10 yield relative traits in DHLs were distributed on 18 chromosomes (except for 1D, 5D and 6D), of which more QTLs were distributed on 1B, 2D, 3B, 6A and 7A(≥10). Some intervals were common shared by multi-trait QTLs on 1B, 2B, 2D, 3B, 3D, 4A, 4D, 5B, 6A and 7A chromosomes; Q.Sn.cgb-1B-3, Q.Ils.cgb-2D-1, Q.Ph.cgb-2D, Q.Sl.cgb-2D-1, Q.Isn.cgb-5A-1, Q.Sn.cgb-6A and Q.Sl.cgb-7B were simultaneously in different years; 4 additive QTLs and 1 pair of epistatic QTL were found significant QEIs with water environment.In present study, QTL analysis for leaf length, width and leaf angle of the top three leaves, CL, CW, SH, GL and GW were dissected for the first time at different treatment, and QTL mapping and genetic basis were also dissected for the traits associated with important physiology and yield under different water regimes. The results rvealed the genetic basis of the complex quantitative traits related to drought stress tolerance, provided a genetic basis and techniques for marker-assisted selection and genetic improvement of drought tolerance. And, some important QTLs with stable expression and some important hot-spot chromosome regions for specific traits played critical roles to QTL functional research and clone based on mapping. |
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