Objective This study aimed to investigate genetic variation in early growth traits across diverse Populus germplasm resources, identify high-growth-performing individuals, and characterize the genomic differences underlying growth performance. The findings provide insights into the genetic basis of poplar growth and inform genomic-assisted breeding strategies.

Method Thirty-two Populus germplasms resources were assessed using growth traits measured in greenhouse-cuttings (shoot height, ground diameter, leaf number of shoot, and shoot dry weight) and field performance indicators (plant height and ground diameter). Selective sweep analysis based on F_st and π ratio were conducted, and these results were integrated with variant detection to identify genetic variations associated with growth traits.

Result Joint analyses of greenhouse and field phenotypes showed that P. × canadensis ‘Guariento’, P. ‘Senhai2’ and P. deltoides ‘zhongcheng1’ exhibited excellent growth performance, whereas P. alba ‘Yx-3’, P. alba, and P. deltoides ‘278-1’ showed poorer growth performance. Selective sweep analysis based on F_st and π ratio identified 172 genomic regions with strong selective signals. Compared with the high-growth-performing P. × canadensis ‘Guariento’, fewer specific structural variant loci were detected in the low-growth-performing P. deltoides ‘278-1’. By integrating selective sweep signals with variant detection, five candidate genes potentially associated with growth traits in poplar were preliminarily identified. Notably, significant phenotypic differences were observed among different genotypes at the site of 21 467 410 bp within Potri.003G220400. Furthermore, the relative expression level of this gene was significantly higher in Populus germplasms with high-growth-performing compared to those with low-growth-performing.

Conclusion Substantial variation exists in growth traits among Populus germplasm resources. Growth differences are unlikely to be driven by a single gene; rather, they appear to result from the combined effects and interactions of multiple genes.