QTLs underlying inflorescence architecture in sorghum (Sorghum bicolor (L.) Moench) as detected by association analysis

Abstract

The pattern of the panicle is an important characteristic of sorghum that is used to identify race divisions and species values. The knowledge of the genetic basis of sorghum inflorescence architecture and its component traits can enhance the process of improvement in sorghum breeding. This study was undertaken to better understand the genetic basis of sorghum inflorescence architecture and its association with yield-related traits. We investigated 98 simple sequence repeat maps in the sorghum diversity research set (SDRS) of 107 landraces from the worldwide sorghum germplasm. A significant difference between accessions was observed for 14 measured traits. In several components of sorghum inflorescence architecture, we found that the significance and high correlations between pairs of traits revealed that these variations are dependent not only on the panicle length (PanL) but also on the total branch number, maximum length of the primary branch (MaxLBZ/MxLBZ) , rachis length (Rac), and panicle diameter (PanD) and width (Panw). Significant mean squares were obtained for almost all characters in the individual analysis and combined analysis of variance for each season and across two seasons, suggesting that, the components of inflorescence architecture and yield related traits were highly variable in SDRS population, therefore, would respond to selection for yield improvement. Molecular markers divided the germplasm into three sub-populations with different groups of inflorescence/panicle types (PanT) (broom, open and compact). The SDRS was composed of six different PanT that were associated with 14 inflorescence traits. Using different models of association analysis, 16 loci on 8 chromosomes were found to be significantly related to the patterns of observed panicle traits. Among these loci, four QTLs were responsible for length-based traits, and three QTLs were responsible for dimentional traits. Four QTLs were responsible for panicle feature such as PanT and shape, one QTL responsible for yield related trait such as grain weight. Two QTLs were responsible for branch-based traits, such as the total node number and branch number with −Log10 (P) values ranging from 1.5 to 7.6 as the threshold value. Several genomic regions affected multiple traits, including one region that affected PanL and MxLBZ/MaxLBZ. QTLs for different traits tended to be found in the same region on chromosome 4 and on chromosome 9. Additionally, QTL was involved on Chr-2, Chr-5, Chr-6 and Chr-10 as a novel QTL that controlled Rac, total node number, PanD and PanT. These results will serve as preliminary findings of QTLs for sorghum inflorescence architecture, and a further evaluation of the germplasm for these traits is in progress. Moreover, these findings can lead to the emergence of a new era of sorghum genomics, which are aimed at bridging the knowledge gap between genotype and phenotype in sorghum inflorescence architecture.