Genetic Analysis For Grain Characteristics In Common Wheat

Grain weight is an important factor in determining the level of wheat production, andalso is one of the main objectives in high-yield wheat breeding. Grain size is an importantdeterminant of the level of grain weight, while grain length, width, thickness and qualityparameters such as unit testing are also the important indicators of wheat quality. Thesecharacteristics of wheat are closely related to grain yield and quality, so genetic analysis ofthese traits is crucial.0911-46, the female parent, which has bigger grain size and grain weight, crosses with“42wheat”, which is relatively smaller in each trait, and produced six pedigrees generations（P₁, P₂, F₁, BC₁, BC₂and F₂）. The methods of multiple generations of conjoint analysis ofmajor gene plus polygenes mixed inheritance model were used for genetic analysis, madegrain weight, grain length, grain thickness and grain width as the target traits, so as tounderstand the grain trait genetic regularity of common wheat. Then took the F₂as mappingpopulation and used SSR markers to construct genetic linkage maps, combined with4seedtraits （grain weight, grain length, grain width, grain thickness） of per plant in F₂populations’phenotypic data, and used Icimapping v3.2software for the grain traits QTL analysis.The results of genetic models demonstrated that the grain weight, grain width and grainthickness conformed to the two additive-dominant-epistatic major genes plusadditive-dominant-epistatic polygenes genetic model. Two major genes of grain weight havepositive additive effects that can increase grain weight. Both positive and negative interactioneffect was found between two major genes. Because of the similar effect size, the interactioneffect was canceled each other out, so little effect was found on grain weight. The dominanteffect of grain width and grain thickness was positive, which was helpful for increasing grainvolume. Grain length conformed to the gene model of additive-dominant-epistemic and hadno main gene. The major gene plus polygene genetic heritability of grain weight ofsegregating generations （BC₁, BC₂and F₂） were88.02%,78.53%and87.82%, respectively.The polygenic genetic heritability of grain length in segregating generations were71.95%,61.64%and62.93%, respectively. Grain width major gene plus polygenic inheritance rate ofsegregating generations were43.9%,32.69%and68.47%, respectively. Grain thickness majorgene plus polygenic inheritance rate of segregating generations were50.01%,42.86%and68.63%, respectively. Among all grain characters, the heritability of wheat weight is thehighest, which indicated that wheat weight is a stable character, and weakly affected by the environment.A total of1281pairs of SSR primers of the wheat genome were used in this study fordetecting polymorphism of the two parental wheat0911-46and42.358polymorphismprimers were screened between the two parents, and the polymorphic primers detection ratewas27.95%. Further screening group between the358pairs of primers,197pairs of primersin the population were polymorphism, which accounting for55.01%of the polymorphicmarkers. The Icimapping v3.2software was used to build21linkage map of the genome of A,B, D, and161pairs of SSR primers targeted to the linkage map. Map length was1760.5cM,the average genetic distance between the marks was10.93cM, and average linkage groupcontaining the7.67mark.1A,4B,6B,7B,7D chromosome contained the most markers （9markers）,2A,3A,4A,1B,2B,3B,3D,4D,5D chromosome contained8markers,5A,7A,5Bchromosome contained7markers,6A,2D,6D had6markers, and1D had only5markers.The study detected9grain weight QTL, and distributed in1A,5A,6A,7A,2B,4B,5Band6B chromosomes, respectively. Phenotypic variance of a minimum which can beexplained was6.54%, and the maximum was16.25%. Compared with previous results,1Aand2A chromosomes were related to, which showed that these two chromosomes maybe hadstable weight QTL, and new QTL was detected in3D and5D, which riches the existingdetection result. Detected30grain size QTL, including6grain length QTL,20grain widthQTL and4grain thick QTL. Grain length QTL located in2A,5A,1B,6B,7B, and5Dchromosomes, grain width QTL distributed in1A,2A,3A,4A,5A,1B,4B,5B,6B,7B,2D,4D and7D chromosomes, and grain thickness QTL distribution5B,3D,4D,7Dchromosomes. Phenotypic variance of a minimum which can be explained was6.30%in thechromosome1B, and the maximum was17.74%in the chromosome7D. Compared with theprevious studies, we found2A and5A chromosome were closely related to wheat grain length.There was stable grain width QTL in1A,2A,5B chromosome. Further research is needed toconfirm whether there was QTL for grain thickness in3D chromosome. The study detectedthree different seed traits of QTL in2A,6B,3D and7D chromosomes, and showed that thesefour chromosomes had strong correlation with wheat seed traits, in particular chromosome2A,stable grain weight and grain length QTL great possibility,and need to attach importance tothese in future studies.This present study provided the basis and reference for wheat molecular genetics andbreeding research, and established a certain foundation for further QTL fine mapping andmarker-assisted selection of high yield and quality of wheat varieties.