QTL Mapping Of Agronomic Important Traits And Development Of KASP Markers In Wheat

Wheat（Triticum aestivum L.）is one of the most important food crops in the world.It is an important factor to improve wheat yield per unit area or total yield and meet the needs of a large population in order to ensure food security and social stability.In recent years,with the decrease of cultivated land area,the increase of biological and abiotic stresses and the change of climate conditions,wheat production is facing more severe challenges.The in-depth research on the genetic mechanism of agronomic important traits in wheat and the discovery of the main effect QTL related to yield traits will play an important role in promoting the cultivation of high-yield wheat varieties and the increase of wheat yield.In this study,the RIL population（F₅）of 181 lines constructed by“Cunmai 1×Jimai 22”was used as the material.The 50K-SNP array was used to detect the population genotype,and a high-density genetic map was constructed.QTL mapping analysis was carried out for 9agronomic important traits in wheat,including plant height、spike length、spikelet number per spike、spike number per plant、kernel number per spike、thousand-grain weight、grain length、grain width and heading date,the main QTL locus controlling the agronomic important traits in wheat was excavated and the high-throughput kasp marker closely linked to the target QTL was developed as a molecular marker.The main results are as follows:（1）According to the results of a 50K-SNP array,a total of 4655 markers isolated in the population were screened.A genetic map containing 4495 SNP markers was constructed by Join Map 4.0 on all the 21chromosomes with the total length of 2455.50 c M,and the average density of 0.55 c M.Among them,the A subgenome has 1200 markers（26.7%of the total number of markers）with the total length of 819.39 c M,and the average density of 0.68 c M;the B subgenome has 1966 markers（43.7%of the total number of markers）with the total length of770.16 c M,and the average density of 0.39 c M;the D subgenome has 1329 markers（29.6%of the total number of markers）with the total length of 865.95 c M,and the average density of 0.65c M.（2）Based on the constructed high-density genetic map,9 agronomic important traits in wheat were mapped by QTL.A total of 46 QTLs were detected,distributed on the chromosomes of 1A（2）、2A（3）、3B（1）、4A（2）、4B（2）、4D（1）、5B（12）、5D（3）、6A（1）、6B（2）、6D（6）、7A（4）、7B（3）and 7D（4）.Among these QTLs,there were 6、6、2、2、6、7、6、4 and 7 QTLs that controlled plant height、spike length、spikelet number per spike、spike number per plant、kernel number per spike、thousand-grain weight、grain length、grain width and heading date,respectively.The phenotypic variation was 5.59-13.18%.Among them,the additive effect of17 QTLs was negative,that is,the synergistic gene came from Cunmai 1,and the additive effect of 29 QTLs was positive,that is,the synergistic gene came from Jimai 22.（3）A total of two QTL clusters were obtained in this study.One was located between the markers AX-95654521-AX-94402033 on chromosome 4A,and the corresponding physical interval was 722.97-726.30 Mb,including QTLs（QGl.sdau-4A.1、QTgw.sdau-4A.1）that controlled grain length and thousand-grain weight.The other is located between the markers AX-108816181-AX-89357512 on chromosome 5B,and the corresponding physical interval is507.94-510.73 Mb,including QTLs（QGl.sdau-5B.1、QGw.sdau-5B.1 and QPh.sdau-5B.2）that controlled the grain length、grain width and plant height.（4）According to the QTL mapping results,the QTL with larger effect value was selected and its peak SNP was transformed into kasp marker.Among them,6 QTLs（QGl.sdau-4A.1、QGw.sdau-7D.2、QHd.sdau-4D.1、QSns.sdau-2A.2、QTgw.sdau-5D.1、QTgw.sdau-6D.1）related to grain length（1）、grain width（1）、heading date（1）、spikelet number per spike（1）and thousand-grain weight（2）have successfully developed tightly linked KASP markers.The above-mentioned KASP markers developed were further verified using the“Cunmai 1×Jimai22”RIL population,it provides a rapid and high-throughput marker for the marker assistant selection of agronomic important traits in wheat such as grain length、grain width、heading date、spikelet number per spike and thousand-grain weight.