| 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 was 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.To make advances in wheat breeding, it is important to study germplasm diversity of winter wheat accessions, and identify SSR markers associated with important agronomy traits. In this study, we selected 136 historical winter wheat accessions planted in northern China. 117 SSR markers evenly distributing on the chromosomes of wheat were used to reveal the genetic diversity. In addition, we found alleles for reducing plant height in 136 accessions. (1) Under rainfed (drought stress) and well-watered conditions, important agronomic traits including morphological traits plant height (PH) , physiological traits (Canopy temperature,CT), growth period (heading date (HD) and flowering date (FD) and yield-related traits (spike length (SL), spikelet number (SN), grain number per spike (GNS) and thousand grain weight (TGW)) were investigated in one years; (2) Seedling biomass (SB) (under drought stress and well-watered) are investigaed. Association analysis were analyzed for these target traits, and explored elite alleles in two environmental conditions that had impacted on these target traits, as well as relatonship between target traits. Main research results were as follows:1. A total of 1484 alleles of loci were detected from the accessions. The average alleles per locus were 12.6 which varied from 2 to 42. The polymorphism information content (PIC) value ranged from 0.016 to 0.941, with an average of 0.640. Most of the similar varieties were cultivated by the same breeders or belonged to the similar ecotype. Some of them were in accordance with the pedigree information. The most varieties cultivated in different ages also clustered together. 2. A total of 19 significant marker-plant height associations were identified (P<0.01) under drought stress. Among them, Xbarc168 (2D), Xgwm285 (3B), Xgwm126 (5A), Xgwm95 (2A), Xgwm212 (5D) and Xwmc396 (7B) were significantly associated with plant height (P<0.001). In well-watered environment, a total of 19 significant marker-trait associations were also identified (P<0.01), of which Xgwm285 (3B), Xgwm95 (2A), Xbarc125 (7D), Xgwm212 (5D), Xwmc396 (7B), Xgwm130 (2B) and Xgwm495 (4B) were strongly associated with plant height (P<0.001). 122 bp was the elite allele of Xgwm95 for reducing plant height.3. 11 significant marker- tiller number associations were identified (P<0.005) under drought stress. Among them, Xgwm193 (6B),Xbarc217 (4D),Xgwm44 (7D),Xgwm11 (1B),Xwmc170 (2A),Xgwm544 (5B),Xcfd53 (2D),Xbarc180 (5A)were significantly associated with tiller number (P<0.001). In well-watered environment, a total of 3 significant marker-trait associations were identified (P<0.005), of which Xgwm515 was strongly associated with plant height (P<0.001). 263bp was the elite allele of Xcfd53 for increasing tiller number.4. A total of 26 significant marker- heading date associations were identified (P<0.005) under drought stress. Among them, Xwmc170 (2A),Xbarc180 (5A),Xgwm471 (7A),Xgwm44 (7D),Xgwm294 (2A),Xgwm11 (1B),Xwmc631 (1B),Xcfd43 (2D),Xgwm193 (6B),Xbarc125 (7D),Xgwm458 (1D),Xgwm544 (5B),Xgwm82 (2A),Xgwm539 (2D),Xcfd53 (2D),Xgwm169 (6A) were significantly associated with heading date (P<0.001). In well-watered environment, a total of 13 significant marker-trait associations were identified (P<0.005), of which Xgwm193 (6B),Xgwm130 (2B),Xbarc42 (3D),Xgwm247(3A),Xgwm296 (2D),Xgwm389 (3B),Xgwm484 (2D),Xbarc125 (7D),Xgwm131 (7B),Xwmc631 (1B),Xcfa2173 (4A)å'ŒXgwm126 (5A) were strongly associated with heading date (P<0.001). 231bp and 157 bp were the elite allele of Xgwm294, Xgwm484 for discreasing heading date, respectively.A total of 6 significant marker- flower date associations were identified (P<0.005) under drought stress. Among them, Xbarc125 (7D),Xgwm294 (2A),Xbarc217 (4D) and Xgwm232 (1D) were significantly associated with flower date (P<0.001). In well-watered environment, a total of 6 significant marker-trait associations were identified (P<0.005), of which Xbarc217 (4D) was strongly associated with flower date (P<0.001). 137 bp was the elite allele of Xgwm232 for making flowering date earlier.5. Xgwm52 (3D) was identified (P<0.001) significantly associated with spike length under drought stress. In well-watered environment, a total of 6 significant marker-trait associations were identified (P<0.005), of which Xgwm130 (2B),Xgwm52 (3D),Xgwm526 (2B),Xgwm538 (4B) were strongly associated with spike length (P<0.001). 152bp and 135 bp were the elite alleles of Xgwm52 and Xgwm526, for increasing spike length, respectively. In well-watered environment, a total of 2 significant marker-trait associations were identified (P<0.005), of which Xbarc125 (7D) and Xbarc81 (1B) were strongly associated with spike number (P<0.001). 177 bp was the elite allele of Xbarc125 for increasing spike number.Xgwm11 (1B) and Xcfd53 (2D) were identified (P<0.001) significantly associated with TGW under drought stress. In well-watered environment, a total of 7 significant marker-trait associations were identified (P<0.005), of which Xgwm429 (2B) and Xgwm296(2D) were strongly associated with TGW(P<0.001).196 bp,257 bp and 205 bp are the elite alleles of Xgwm11,Xcfd53and Xgwm429 for increasing TGW, respectively.There is no marker associated with SN and GNS under drought stress. In well-watered environment, Xwmc396 (7B),Xgwm292 (5D) and Xbarc181 (1B) associated with SN (P<0.005), Xwmc396 significantly associated with SN(P<0.001). 151bp was the elite allele of Xwmc396 for increasing TGW. A total of 6 significant marker-trait associations were identified (P<0.005), Xgwm193 (6B) significantly associated with GNS (P<0.001). 169:179bp is the elite allele of Xgwm193.6. Xbarc125 (7D),Xgwm539 (2D),Xgwm95 (2A) and Xcfd23 (4D) associated with CT under drought stress (P<0.005). Xgwm517 (7B),Xgwm285 (3B) and Xbarc177 (5D) significantly associated with CT(P<0.001), Xbarc177 significantly associated with CT(P<0.001). 265bp is the elite allele of Xgwm193.In present study, association analysis for PH, TN, SN, SL , CT and TGW were dissected for the first time at different treatment, and association analysis 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 markers with stable expression and some important alleles for specific traits played critical roles in breeding research and clone based on mapping.With the rapid development of molecular biology and genomics, it is expected to utilize association analysis more widely in genetic research, germplasm enhancement and breeding in wheat. |
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