Unraveling the genetic architecture and candidate genes underlying dynamic growth in Populus deltoides ‘Danhong’× Populus simonii ‘Tongliao1’

Plant growth, particularly in perennial tree species, is a dynamic trait governed by multiple factors including temporal variation and environmental influences. Although numerous quantitative trait locus (QTL) mapping studies have focused on phenotypes at specific time-points, the genetic architecture of dynamic growth traits remains poorly understood. In this study, we conducted a dynamic characterization analysis of seedling height (SH) and ground diameter (GD) in hybrid population of Populus deltoides ‘Danhong’ (DHY) × Populus simonii ‘Tongliao1’ (XYY) during the first growth season. Integrated Fun-map and FVT-map analyses identified eight overlapping QTLs associated with poplar dynamic growth in poplar, which displayed late expression patterns throughout the first growth season. Based on tissue expression pattern, six genes with high expression in pre-dormant bud, phloem and xylem were preliminarily identified as candidate genes associated with poplar growth. Among them, ARABINOKINASE coding gene PtARA1 was identified, which plays important roles in keeping the balance of L-arabinose in plant cell wall. eQTL analysis revealed that a non-synonymous single nucleotide variation (SNV) at the exon region of PtWRKY89 significantly increased the expression level of PtARA1 in xylem. The individuals carrying this variation exhibited poorer growth than those without it, which further proves the crucial role of PtARA1 and PtWRKY89 in poplar growth. This study provides mechanistic insights and candidate genetic targets for advancing poplar improvement through molecular breeding strategy.