Mapping Quantitative Trait Loci And Developing Molecular Markers For Salt Tolerance In Wheat

Land salinization severely limits the normal growth of plants,reduces the yield of crops,and seriously threatens global food security.Saline soil is widely distributed in our country and is increasing year by year,resulting in a decrease in available arable land and restricting the development of agriculture in our country.Wheat(Triticum aestivum L.,2n=6x=42,AABBDD)is one of the most important food crops in the world and it is one of the three main staple food crops in our country.Wheat is not only the main crop planting on the saline land,but also plays an important role in the management and improvement of saline-alkaline land.Therefore,studying the growth and development characteristics of wheat under salt stress conditions,mining the advantages of wheat itself and key genes for salt tolerance can provide valuable genetic resources for the cultivation of salt-tolerant wheat varieties.In order to clarify the genetic characteristics of salt tolerance traits and salt tolerance genes in wheat,the main quantitative trait locus(QTL)related to wheat root traits under salt stress conditions was correlated,and a linkage was provided for the application of the main salt tolerance QTL molecular marker.In this study,the Recombinant Inbred Lines(RIL)of "Dou Mai × AK 58" was used as the research material to study the salt tolerance mechanism of wheat.The RIL population and its parents were first planted in Haixing Saline-alkali land in Hebei Province.Field investigations revealed that the population and its parents had salt tolerance phenotype differences.Then,the Na Cl gradient screening was carried out in the laboratory.The results showed that at 100 m M Na Cl,the roots phenotypic difference is extremely significant.It was determined that 100 m M Na Cl solution and 1/10 of Hoagland nutrient solution were used to cultivate the parent and RIL populations,and the wheat salt tolerance research was conducted.By investigating the growth of the root system at the seedling stage of wheat,and count the root length and root dry weight of wheat under normal conditions and salt treatment conditions,calculate the relative total root length(R-TRL),relative average root length(R-ARL),root to shoot ratio,relative root dry weight(R-RDW)and other indicators.The analysis of the results showed that the above root traits were all continuously distributed,and the phenomenon of super-parental segregation appeared,indicating that these root traits are all complex quantitative traits regulated by multiple genes.Among them,the frequency distribution histogram of R-ARL and R-RDW is more in line with the normal distribution,so the R-ARL and R-RDW are used as indicators to identify whether wheat is salt-tolerant.At the same time,the laboratory uses R-ARL and R-RDW to identify salt-sensitive strains and salt-insensitive strains,which mutually confirms the growth results of the RIL population grown in the saline-alkaline land of Haixing,Hebei.It shows that it is feasible to use 100 m M Na Cl for salt stress in the laboratory.It also indicates that QTL analysis using the R-ARL and R-RDW as the salt tolerance indicators of wheat has a certain degree of credibility.The 55 K gene chip was used to genotype 111 lines in the RIL population.Based on the scan results of the chip combined with the phenotypic data of R-ARL and R-RDW,QTL analysis was performed,and seven QTLs with LOD ≥ 2.5 were located,namely Qrdw-1D1,Qrdw-1D2,Qarl-2A,Qarl-3B1,Qarl-3B2,Qarl-4A,Qrdw-4D and Qarl-5A.Among them,the QTL loci controlling the R-ARL are Qarl-2A,Qarl-3B1,Qarl-3B2,Qarl-4A and Qarl-5A,Qarl-2A and Qarl-4A are located on the long arms of chromosomes 2A and 4A,respectively,Qarl-3B1,Qarl-3B2,and Qarl-5A are located on the short arms of chromosomes 3B and 5A;the QTL loci controlling R-RDW are Qrdw-1D1,Qrdw-1D2 and Qrdw-4D,Qrdw-1D1 and Qrdw-4D are located on the short arm of chromosome 1D and 4D,and Qrdw-1D2 is located on the long arm of chromosome 1D.Among the above-mentioned sites,Qarl-4A can explain the highest contribution rate of phenotype,which is 28.106%,and its additive effect comes from Dou Mai.And using different mapping software and QTL analysis software can identify the site,it will be the key research object of this study.Develop molecular markers for the site Qarl-4A(Qarl-4AM1 etc.)for subsequent screening of remaining hybrids and provide a choice for wheat salt-tolerant molecular marker-assisted breeding.In summary,R-ARL and R-RDW are reliable indicators for the identification of wheat salt tolerance.In this paper,eight QTL loci have been mapped and molecular markers have been developed for the major QTL loci Qarl-4A.It has application value for developing wheat salt tolerance research and molecular marker-assisted breeding.