Genetic Dissection Of Quantitative Traits Loci For Heat Tolerance Index And Traits Associated With Heat Tolerance In Winter Wheat (triticum Aestivum L.)

The wheat (Triticum aestivum L.) belong to cool crop, and was affected by hightemperature during growing season, especially during later growing season. And the resulttended to drop grain yield and quality. The optimum temperature for grain filling was during20～24℃. When the temperature was above25℃, the time for grain filling will be shorten,the shoot will be premature senility and grain will be affected. From this sence, the impact ofthe wheat from high temperature is likely to be regular. Currently development of molecularquantitative genetics provided an effective method to study the genetic mechanism of heatresistance and its genetic patterns for complex quantitative traits. So, it is of very importancethat map QTLs and dissect genetic factors for complex quantitative traits associated with heattolerance in wheat molecular breeding of heat tolerance.Doubled haploid lines (DHLs) previously constructed by a cross between Hanxuan10andLumai14, two common wheat cultivars, being selected for experimental materials in presentstudy. Some of the important traits associated with heat-tolerance including content ofchlorophyll (CC), fluorescence parameter of chlorophyll (CFP), root dry weight (RDW),shoot dry weight (SDW), seedling biomass (SB) in different temperature during seedlingstage were investigated in different temperature. And flag leaf raletive water content (RWC),flag leaf natural water content (NWC), canopy temperature depression (CTD), glumewater-soluble carbohydrates (GWSC), neck stem water-soluble carbohydrates (NWSC) andthe rest stem water-soluble carbohydrates (SWSC), thousand-kernel weight (TKW), CC andCFP in grain filling stage were investigated in different temperature and water condition.Quantitative trait loci (QTL) mapping and QTLs×water environment interactions (QEIs) areanalyzed on these target traits in this study. The study mapped the QTLs for those traits andtheir heat tolerance index (HTI) and illustrated the genetic basis and expression regularpattern for heat tolerance of winter wheat.(1) All target traits from DHLs in the test showed significantly sensitive to heat stress andshowed wide variation and transgressive segregations, belonging to complicated quantitativetraits controlled by the tiny effect polygene and regulated by minor-effect polygenes whichwere easily affected by different environments. Total of31additive QTLs and39epistatic QTL of HTI for target traits and total of118additive QTLs and149epistatic QTL of thetarget traits were detected in two development period. And the genetic effect and theinteraction effect for QTL×environments were estimated and analyzed in this study.(2) The5additive QTLs and8epistatic QTL related to HTI of seedling traits, and8additive QTLs and20epistatic QTL related to seedling traits were located on allchromosomes except4D and6D under two temperature conditions. From the distribution ofthe QTLs detected by the test, the QTL for seedling traits mainly distributed on thechromosomes2D,6B,3A,4A,5A and7A, and that for HTIs mainly on the chromosomes6A,6B,3A,2D,5A and7A. The genetic effect of the QTLs for seedling traits mainly wasepistatic effect and their HTI mainly was additive effect. The phenotypic variance explainedby single additive QTL and single epistatic QTL controlling the HTI of seedling traits werefrom5.14%to12.41%and from1.44%to3.61%, respectively. And that for controllingseedling traits were from0.32%to8.81%and from0.71%to0.32%, respectively.(3) Total26additive QTLs and31epistatic QTLs for TKW, CC, CFP, RWC, CTD,GWSC, NWSC and SWSC in grain filling stage were detected on chromosome1A,1B,2D,3A,5A,5B,6A,6B,7A and so on. The phenotypic variance explained by single additiveQTL and single epistatic QTL for those QTLs were from2.64%to11.41%and from0.99%to8.84%, respectively. The genetic effect of4of the26additive QTLs were above10%. Thegenetic effect for HTLs of TKW, CC, GWSC, NWSC and SWSC mainly were additive effect,and that of RWC, CFP, CTD mainly were epistatic effect. The correlation coefficients amongthe HTI of GWSC with the most of other traits were highly significant.(4) The heat-resistance QTL of the DHL were compared and analysed in seedling stageand grain filling stage, and the result showed that interaction effect QTL×environment wererelatively small in seedling stage than in grain filling stage. The genetic mechanisms of theQTL for the two development stage were not very consistent, and there are some commonpoint bwtween them, that is the number of the QTL on6A，3A and6B were more in the twostage, and the additive effect was the main for those QTL. Some of the additive QTL in thetwo stage were detected on the same or close site. For instance, both of the QTL(Q.Sb.cgb-3D) for HTI of SB in seedling stage and the QTL (Q.Itgw.cgb-3D) for HTI ofhousand-kernel weight (TKW) in grain filling stage were deteced at the place1.8cM from theright mark between Xgwm456-Xgdm8on3D. And both of the QTL (QCc.cgb-2D.1) for HTIof CC in seedling stage and the QTL (Q.Itgw.cgb-2D) for HTI of RWC in grain filling stagewere deteced between P3176.1-P1123.1. This suggested that there may be some "permanent"expressed genes for the genetic of heat tolerance in wheat, and they play the regulatory rolefor heat tolerance in the whole growth period. (5) Total13additive and26epistatic QTL for RWC, NWC and CTD between differentheat stress time were detected in grain filling stage. And the QTLs for RWC mainlydistributed on chromosome2B,3B,5B,6A, and the QTLs for NWC mainly on2B,3B and3Dand the QTLs for CTD mainly on1B,2B and3B. The genetic effect of the epistatic QTLs andepistatic QTLs×environment were larger than additive QTLs. The genetic effects for NWCunder heat-stress for7days was the most, and the contribution for phenotypic variation was64.5%.(6) CC and CFP were sensitive to temperature environment condition and may be usedas parameter for heat tolerance in grain filling stage. They essentially were subjected to thecomplex quantitative traits regulated by minor-effect polygenes which were easily affected bydifferent environments. Total of21additive and39epistatic QTL for CC and CFP weredetected. The QTLs for CC mainly distributed on chromosome1B,2D,4B,5A and6A, andthat for CC mainly on chromosome1B,3A,3B and4A. Three QTLs (Q.Ccu.cgb-1B.1,Q.Ccf.cgb-5A.1and Q.Ccf.cgb-2D) had large contribution were detected in the test, and theircontribute for phenotypic variation were19.40%,8.88%and7.39%, respectively.(7) The12traits for GWSC, NWSC, SWSC and their remobilization were detected in grainfilling stage, and all of them belong to complex quantitative traits regulated by minor-effectpolygenes. Total of46additive and25epistatic QTL for target traits were detected, and mostof them on chromosome1B,2A,2Dand so on. Some of the QTLs for the three traits wereshared the same intervals, that is, C436-Xgwm44on7D, WMC170-Cwm96.2on2D andP4114.1-P6934.2on7A. The QTL clusters were detected on chromosome2A,2D,3A,3D,7A and7D. The genetic effect of the targets traits mainly were additive effect.(8) Total of30additive and39epistatic QTLs for grain weight developmental behaviourwith unconditional and conditional method were detected, and mainly distributed onchromosome1B,4B,2D,2A,7B,3B,4A and6A. The locus for unconditional grain weightmainly distributed on chromosome1B,3B,4B and7B, and that for conditional grain weightmainly distributed on chromosome1B、2D、4A and4B. The QTL clesters were detected onthe intervals of P3474-480-T122on1B, WMC453.1-WMC144on2D, Xgwm644.2-P2076-147on3B. The genetic effect for unconditional grain weight mainly wereadditive effect, and that for conditional grain weight mainly were epistatic effect. The effectof QTL×environment with unconditional and conditional method were minor. The testpredicted superior alleles constituted with the superior polygene by the total genetic effects ofknown QTL from individual DHLs.