Identification Of Seed Dormancy Loci And Cloning Of The TaQsd1 Gene And Development Of Functional Markers In Wheat(Triticum Aestivum L.)

Pre-harvest sprouting(PHS)in common wheat,as a worldwide problem,affects yield and quality.Identification of seed dormancy loci and their regulatory genes can reduce PHS.In this study,SSR markers were used to identify seed dormancy QTLs in the Jimai 20×Suiningtuotuomai recombinant inbred line(JS-RIL)population.The markers developed by Wheat 660K chip were used to encrypt QTLs,the major seed dormancy loci Qphs.ahau-5BL was identified on chromosome 5B.At the same time,BSR-seq was carried out by using the "25+25" extreme dormancy lines mixing pool,and then identify three candidate genes enriching SNP in the Qphs.ahau-5BL through it.In addition,previous identified the qsd1 gene controlling the seed dormancy on the chromosome 5H of wild barley.In this study,the homologous gene TaQsd1 were cloned in wheat,and functional markers were developed.The transcript and protein levels of TaQsdl-5B in different dormant varieties were analyzed,and we investigated the distribution of the TaQsd1-5B alleles in wheat germplasm resources in many countries of the world.The results of this study will be conducive to the analysis of seed dormancy regulation mechanism.1.Whole-genome QTLs of seed dormancy were analyzed in the JS-RIL population using SSR markers,and seed dormancy loci existed in 19 chromosomes except 4B and 7D.Based on the results of 660K-BSA analysis,the CAPS marker was developed.The seed dormancy locu(Qphs.ahau-5BL)was finely mapped between AX6652-gwm408(distance 4.12Mb)on chromosome 5B.In combination with BSR-seq,CNGC2,WRKY57 and PP2C were identified in the target region,respectively.2.TaQsd1 genes were cloned by Homology-based cloning and TaQsd1-5B has multiple variations.Two CAPS markers and one KASP marker based on SNP variation on exons 3 and 11 and promoter(QSD1-QSD3)were developed.The Yangxiaomai×Zhongyou 9507 RIL population and the natural population consisting of 351 wheat varietes verified that the above three markers significantly correlated with seed dormancy traits(p<0.01).QTL analysis showed that QSD1 co-separated with Qpd.ahau-5B and explained 8.68%-21.63%phenotypic variation in different environments.3.The expression of TaQsd1-5B was major in embryos and the relative expression level of TaQsdl-5B was decreased significantly within 0-6h after seed imbibition but increased slightly within 6-12h.The transcript levels of TaQsd1-5B in varieties with long period of dormancy were significantly higher than that in short dormancy varieties.In addition,the activity of the AlaAT encoded by TaQsdl-5B is consistent with the transcript levels during seed imbibition.These results indicated that TaQsd1-5B positively regulate seed dormancy.4.Compared with short dormancy varieties,long dormancy varieties had significantly higher endogenous ABA content and expression levels of genes related to ABA synthesis and signaling pathways,and lower expression levels of genes related to ABA metabolism.5.The frequency of TaQsd1-5Ba associated with long dormancy in Chinese landrance was higher than in modern varieties;but the frequency of TaQsd1-5Bb associated with short dormancy was dominant in foreign germplasms.