Polymerization of beneficial plant height QTLs to develop superior lines which can achieving hybrid performance levels.

Abstract

Heterosis, a key technology in modern commercial maize breeding, is limited by the narrow genetic base which hinders breeders from developing superior hybrid varieties. By integrating big data and functional genomics technologies, it becomes possible to create new super maize inbred lines that resemble hybrid varieties through the aggregation of multiple QTL parental advantage loci. In this study, we utilized a combination of resequencing and field selfing selection methods to develop three pyramiding QTL lines (PQLs) (PQL4, 6, and 7), each containing 15, 12, and 12 QTL loci respectively. Among the three PQLs, PQL6 (266.78 cm/119.39 cm) demonstrated hybrid-like performance comparable to the hybrid (276.96 cm/127.02 cm) (P < 0.05). Testcross between PQL6 and the parental lines revealed that PQL6 had accumulated and fixed advanced parent alleles for superior traits in plant and ear height. The significant increase in PQL6 plant height primarily resulted from the aggregation of two major effective QTL (qEH2-1 and qEH8-1 on chromosomes 2 and 8), indicating that the aggregation of major effective QTL is a key selection indicator. Furthermore, PQL6 exhibited slow vegetative growth but experienced a rapid height increase during the reproductive stage, particularly in the 1-2 weeks before flowering, when its growth rate accelerated and surpassed that of the hybrid varieties. Our study explored the time period and key parameter indicators for molecular breeding of maize, providing a theoretical concept and practices for further complex multi-trait design and aggregation.

Supplementary information: The online version contains supplementary material available at 10.1007/s11032-025-01546-4.