| Drought stress is a major environment constraint greatly impacting wheat (Triticum aestivum L.) production in many arid and semi-arid areas of the world. Drought tolerance is a complex quantitative trait; it is very essential for genetic improvement of drought tolerance to dissect quantitative loci for physiological and morphological traits involved in the drought tolerance in wheat.Doubled haploid lines (DHLs) (Hanxuan 10×Lumai 14) and recombinant inbred lines (RILs) (Opata85×W7984) were selected as experiment materials in this study. Important traits associated with drought tolerance including physiological traits (chlorophyll content (ChlC) and parameters of chlorophyll fluorescence kinetics (PCFK)) and agronomic traits (plant height, number of tiller per plant (NT), spike number per plant (SNP), number of setting spike per plant (NSSP), ratio of setting spike number to maximal tiller number (RSST), ratio of setting spike number to total spike number (RSSS), biomass yield (BY), grain yield per plant (GYP), harvest index (HI) and weight of thousand grain (WTG)) were investigated in different locations and years under two water regimes, drought stress (DS) and well-watered condition (WW). Drought stress coefficient (DS|WW) and drought resistance index (DRI) were estimated for the given traits through conditional analysis to evaluate their special reaction under DS and to assess drought tolerance of them, respectively. QTL for target traits and their derived traits (DS|WW and DRI) were mapped to dissect their genetic mechanism and reveal the hot chromosome region shared by multi-QTLs. The major results were as follows:1. All target traits of DHLs and RILs showed significantly sensitive to drought stress, which was the character of complex quantitative traits. These traits were controlled by QTLs with additive effect and/or epistatic effect. Some QTLs were involved in complex QTL network, and some responded to specific environment, therefore, marker-assisted selection (MAS) for drought tolerance should give attention to both kinds of QTLs.2. Genes of plant height were detected on all chromosomes except 6D. It is deduced that genes of plant height segregate widerly in DHLs than in RILs. QTLs with additive and epistatic effects were the important genetic component for plant height, most of which acted in QTL networks. And additive main effect (A) was the major genetic effect for plant height, which expressed greatly in S1|S0. DS|WW of plant height on ontogeny was mainly affected by environment components. The major genetic component for DRI of plant height was additive main effect, which mainly expressed in S1|S0.3. ChlC in DHLs was mainly controlled by A effect or AA effect in different stages, which were hardly affected by environments. Epistatic effect was the major genetic effect for most PCFK and their derived traits; environments greatly affected these PCFK-related traits.4. QTLs with the additive and epistatic effects being involved in QTL genetic networks were the major genetic basis for WTG, and additive genetic main effect was its main genetic effect. The major genetic effects for NT, SNP, NSSP, RSST, RSSS, BY, GYP and HI were additive, epistatic, epistatic, additive, additive, additive, epistatic and additive effects in turn, which showed sensitive to environments.5. WMC156～P3446.1 on 1B, WMC181～P3470.3, WMC453.1～WMC18～Xgwm30 and Xgwm157～Xgwm539 on 2D, CWM48.1～WMC532 on 3A, Xgwm165.2～Xgwm192 on 4D, WMC410～WMC74～Xgwm291～Xgwm410 on 5A, and Xpsp3071～Xgwm570 on 6A were common regions shared by multi-traits. They were crucial regions for further elucidating genetic basis of drought-tolerant traits.In conclusion, the present research dissected genetically physiological and morphological traits associated significantly with drought tolerance on ontogeny in wheat. The results provided a genetic basis and techniques for improving drought tolerance by molecular breeding in wheat.
|
PDF Full Text Request