Genetic Dissection of Three Major Quantitative Trait Loci for Spike Compactness and Length in Bread Wheat ( L.).

Spike compactness (SC) and length (SL) are the components of spike morphology and are strongly related to grain yield in wheat ( L.). To investigate quantitative trait loci (QTL) associated with SC and SL, a recombinant inbred lines (RIL) population derived from the cross of Bailangmai (BLM, a Tibet landrace) and Chuanyu 20 (CY20, an improved variety) was employed in six environments. Three genomic regions responsible for SC and SL traits were identified on chromosomes 2A and 2D using bulked segregant exome sequencing (BSE-Seq). By constructing genetic maps, six major QTL were repeatedly detected in more than four environments and the best linear unbiased estimation (BLUE) datasets, explaining 7.00-28.56% of the phenotypic variation and the logarithm of the odd (LOD) score varying from 2.50 to 13.22. They were co-located on three loci, designed as , , and , respectively. Based on the flanking markers, their interactions and effects on the corresponding trait and other agronomic traits were also analyzed. Comparison analysis showed that and were possibly two novel loci for SC and SL. and showed pleiotropic effects on plant height and grain morphology, while showed effects on spikelet number per spike (SNS) and grain width (GW). Based on the gene annotation, orthologous search, and spatiotemporal expression patterns of genes, and for , and and for were considered as potential candidate genes, respectively. These results will be useful for fine mapping and developing new varieties with high yield in the future.