Dissecting Gene Network Underlying Wheat Kernel Shape and Size and Their Association with Wheat Quality in an Elite × Non-Adapted Cross Using a High Density SNP Linkage Map.

Wheat (Triticum aestivum L.) kernel morphology, including kernel shape and size has been under selection since it was first domesticated and still remains major breeding target as it is important components of grain yield and quality. So, to gain detailed understanding of the genetics of kernel shape and size traits, a population of 160 RILs developed using an elite genotype (ND 705) and a non-adapted genotype (PI 414566) was evaluated at multiple locations for six kernel shape and size traits (kernel length, width, length/width ratio, area, kernel weight by volume and thousand kernel weight) and three quality traits (flour extraction, grain protein content and kernel hardiness). The mapping population was genotyped using Infinium 90K iSelect SNP assay and a genetic map consisting of 10,172 SNP markers was constructed. The genetic map represented all wheat chromosomes and covered a map length of 4,676.1 cM with the average distance of 0.46 cM between any two markers. Phenotypic analyses indicated that higher values for grain yield, kernel volume weight, and flour extraction were significantly associated with spheroid or round shape (short and plump), large, and heavy kernels. The quantitative trait analysis identified a total of 29 genome regions associated with grain shape and size; majority (>80%) of the region being associated with multiple traits. The analysis showed that kernel length and width had an independent genetic architecture, while a large number (~59%) of the QTL for kernel shape traits, shared the same genomic regions with the QTL for kernel size traits. The most stable and major QTL associated with grain shape and size was identified on 4B and most likely corresponds to a major rice gene GS3. Major and stable loci were also identified in the homoeologous regions of group 5 chromosomes and also in the regions of TaGW2 (6A) and TaGASR7 (7A) genes.  Both the parental genotypes contributed almost same number of beneficial positive QTL alleles suggesting that the non-adopted germplasm has a great potential in enhancing the gene pool for grain shape and size traits and for further yield improvement in in wheat. The results of dissection of epistatic gene networks and the association of grain shape and size with wheat quality and yield will also be reported in this presentation. This study provides new knowledge on the gene network of kernel shape and size and their association with wheat quality, which may aid further improvement in wheat using genomic tools.