Effect of genotype on selected properties of young plantation-grown Eucalyptus pellita F. Muell. and its hybrids for structural applications

Short-rotation plantation hardwoods are increasingly used to meet timber demand but are often harvested before optimal structural properties are achieved. This limits their suitability for high-value timber applications. Improving the mechanical properties of young trees through selective breeding is a viable strategy, particularly when supported by molecular tools. However, limited information exists on how genetic and phenotypic variation influence structural traits across the stem profile. This study assessed variation in the mechanical properties of Eucalyptus pellita and its hybrids to support breeding for structural timber. Modulus of elasticity (MOE), modulus of rupture (MOR), and compressive strength (CS) were measured in inner and outer wood across multiple stem heights. These traits were correlated with physical properties, growth, and chemical traits. A single nucleotide polymorphism (SNP)-based genetic association analysis was also conducted. Outer wood and middle stem positions showed the highest values, with MOE up to 17,700 MPa, MOR up to 147 MPa, and CS up to 70 MPa, particularly in the E. pellita × E. brassiana hybrid. Mechanical traits correlated positively with height and diameter at breast height, while microfibril angle was negatively associated with CS ( r = − 0.30 inner; − 0.24 outer). Lignin content showed positive associations with MOR and CS. SNP-based genetic analysis identified loci linked to MOE and MOR, including SNP4096 near Eucgr. A00211, a candidate gene potentially involved in cell wall regulation and wood strength. These findings highlight the potential of combining phenotypic and genomic tools to improve the selection of fast-grown hardwoods for high-value structural applications.