Identification Of Major QTLs For Grain Weight And Pre-Harvest Sprouting Resistance And Fine-Mapping Of Qphs.ahau-4B In Common Wheat

Wheat is one of the most important food crops in the world.Wheat yield is related to the food security of human beings,and grain weight is an important component of wheat yield,which is greatly affected by grain width and length.Pre-harvest sprouting(PHS)refers to the germination of grains in a ripened wheat spike due to a period of rainfall or high humidity before harvest,which can severely degrade wheat yield and quality of flour products.Therefore,improving grain weight and PHS resistance are important targets of genetic improvement in wheat.Both grain weight and PHS resistance are quantitative traits controlled by multiple genes with complex genetic mechanisms.In our research,a recombinant inbred line(RIL)population derived from a cross between large-grained cultivar "Jing411"(PHS-susceptible)and small-grained landrace "Hongmangchun21"(PHS-resistant)were used to identify major QTLs for grain weight and PHS resistance.Representative molecular markers of these loci were validated in nature populations.The interval of Qphs.ahau-4B,a major QTL for PHS resistance,were narrowed to identify the candidate gene.Main results are as follows:1.Totally,48 TGW-related QTLs,29 GW-related QTLs,and 28 GL-related QTLs were detected in 2 genetic linkage maps constructed by SSR and SNP markers based on different technologies using 3 QTL analysis methods.Of these,five TGW-related QTLs with significant effects were distributed on chromosomes 1BL,ZDL,4BL(2),and 7BS,respectively;three major QTLs associated with GW were located on chromosomes 2DL,4BL,and 7BS,respectively;two GL-related major QTL were detected on chromosomes 2AS and 7AL,respectively.2.Four CAPS markers(1B-JHMfeI,2A-CAPSmin,4B-8621,and 7A-3738)were developed and used to validate the associations of 4 novel major QTLs(Qtgw.ahau-1B.1,Qgl.ahau-2A.2,Qtgw ahau-4B.1 and Qgl.ahau-7A.3)with grain weight/size in 180 Chinese mini-core collection accessions,respectively.3.Eight QTLs related to PHS resistance were identified and distributed on chromosomes 1B(2),3B,4A,4B,5B,6B,and 7D,respectively.Among them,Qphs.ahau-4B and Qphs.ahau-6B with significant effects have not been reported in previous studies.4.The interval of Qphs.ahau-4B was narrowed from 2.25Mb to 154.7Kb by recombination screening in secondary mapping population.Four candidate genes named TraesCS4B02G381900,TraesCS4B02G382000,TraesCS4B02G382100,and TraesCS4B02G382200 were annotated in target region.5.Based on the analysis of differentially expressed genes in BSR-seq,the candidate gene of Qphs.ahau-4B was preliminarily identified as TraesCS4802G382000,with a total length of 4988bp and encoding 593 amino acids,including Ring-type Zinc Finger domain and WD40-repeat containing domain.The functional marker TaE3 was developed based on the sequence differences of TraesCS4B02G382000 between PHS-susceptible and PHS-resistant wheat varieties.TaE3 was significantly correlated(P<0.01)with PHS resistance in 225 Chinese mini-core collection accessions and 255 wheat varieties.