Integrating multi-platform LiDAR phenotyping and GWAS reveals PSK6, AUG8, and WDL4 as key regulators of growth in Populus deltoides

Accelerating the intelligent breeding of Populus deltoides for high-yield timber production requires high-throughput phenotyping and a precise deconstruction of the polygenic networks governing its stem and crown architecture, which is increasingly critical given the rising global demand for wood and the need to boost timber yield per unit area. In this study, UAV and backpack lidar systems were integrated to extract individual tree height and DBH to accurately capture the phenotypic indicators of P.deltoides . Whole-genome resequencing and genome-wide association studies were performed on 233 germplasm resources. Alignment to the reference genome yielded 4,275,812 high-quality SNPs. Population genomic analyses revealed divergent linkage disequilibrium decay patterns between the Anhui and Hubei populations, moderate genetic differentiation, and 86 selection signatures enriched in the TFIID transcription initiation complex and phenylpropanoid metabolism. Integrating FarmCPU and BLINK models, we mapped 19 genome-wide significant SNPs and identified 14 candidate protein-coding genes. Crucially, we identified PSK6 on Chr4 as the primary candidate regulating tree height via cambial cell division. For diameter at breast height, a strong signal on Chr18 implicated AUG8 , a gene essential for microtubule organizing center assembly, in radial growth. Furthermore, WDL4 was identified as a key regulator of crown width, corroborated by transcriptome data showing significantly repressed expression in high crown-width accessions. Collectively, these findings unravel the complex genetic architecture of longitudinal and radial growth in P. deltoides , providing highly specific genetic targets and a robust theoretical foundation for future genomic-assisted and intelligent breeding strategies.