QTL Mapping Of Spike Density And Fusarium Head Blight Resistance In Common Wheat

Bread wheat(Triticum aestivum L.)is one of the most important cereal crops globally and also one of the important sources of nutrition for people.Fusarium head blight(FHB)has gradually risen from a secondary disease to a major disease and it has spread throughout most wheat planting areas in both domestically and internationally with changes in wheat planting systems and other factors.The effect of FHB was not only on the wheat produection,but also on human and animal health.Previous studies showed that a significant correlation between wheat spike density and scab resistance,viz.the higher the spike density,the poorer FHB resistance.However,good plant type usually shows high spike density,compact and upright plant type.According to this,in the present study,we explored new co-located resistance loci to both wheat spike density and FHB by using Yangmai 16/Zhongmai 895 double haploid population provided by the Crops Institute of the Chinese Academy of Agricultural Sciences(CAAS).We are going to provid new genes/loci,new molecular markers and new germpalm for wheat breeder to balance wheat good plant type and FHB resistance.In this study,based on the 660 K SNP genotype data of the DH population of Yangmai 16/ Zhongmai 895,combined with the phenotypes of plant height,panicle related traits and head mould resistance in 4 environments,new loci regulating multiple traits at the same time were identified.The research results listed in below:Based on the phenotype,we found that the correlation coefficient of plant height,spike density and FHB resistance were 0.77-0.95,0.47-0.81 and 0.42-0.67.The broadsense heritability of plant height,spike density and FHB resistance were 0.95,0.92,0.84,respectively.The correlation coefficient between plant height and spike density was 0.25-0.40,The correlation coefficient between spike density and FHB resistance was 0.19-0.43,The correlation coefficient between plant height and FHB resistance was0.27-0.74.Therefore,it can be concluded that there was a significant correlation between FHB and plant height and spike density,and the correlation between FHB and plant height was the highest.Accroding to the genotype,we identified 144,093 polymorphic SNPs among the DH population and used 9,242 SNP markers to construct high-density genetic linkage maps after removing the redundancy molecular markers.A total of 82 linkage groups were constructed,covering 21 chromosomes.The total length of the linkage group was15208.02 c M and the average genetic distance density of a single marker was 1.65 c M.Based on the above phenotype and genotype,we used QTL Ici Mapping 4.2 to perform QTL analysis and mapped 21 QTL associated with spike on wheat chromosomes,of which chromosomes 2D,4A,4B,4D,5A,5D,6B and 7B are significantly correlated with spike density,which can explain the phenotype variation of spike density between3.32%-19.94%;6 QTLs were identified for FHB resistance and located on wheat chromosomes 3B,4B,4D,5A,6D and 7A,respectively.These QTLs can explain phenotype variations from 3.82% to 30.41%;In addition,6 QTL were associated with plant high on chromosomes 4A,4B,4D,5A,6D,and 7D and they can explain phenotype variations from 1.41% to 58.09%.Interestingly,the 2D chromosome QTL showed association with both spike length and spike density,which can explain 4.56%-6.57% and 3.32%-6.94% of phenotype variations,respectively.Among these loci,chromsomes 4B and 4D showed highly association with three traits,which can explain spike density,plant height,and FHB resistance variation of 4.98%-15.83%,9.3%-58.09% and 9.14%-30.41%,respectively.The two loci have tightly linked molecular marker for breeders to improve wheat spike type and FHB resistance.In addition,we also phenotyped 262 Sumai 3-radiation mutants and 200 Gansu landrance materials in order to identify new genetic resources for assocaiton with wheat spike density and FHB resistance under greenhouse.A total of 27 new germplasm were identified with the similar resistance levels to Sumai 3.Among these,16 lines showed extremely low toxin content.Using the molecular markers mentioned above to genotype these lines,a total of 8 lines were found to carry both 4B and 4D loci,with short,high spike density and FHB resistance.Thus,the result of the present sudy was not only provides new loci for balancing wheat spike density and FHB resistance,but also provides new germplasm resources and molecular markers for wheat breeders.