Growth adaptability and stability in Catalpa bungei clones: the role of genetics and environment.

Understanding genotype, environment, and genotype-by-environment (G × E) interactions is vital for effective forest breeding. The Catalpa bungei, valued for its rapid growth and high-quality wood, exhibits uncertain genetic variation in growth across diverse ecological conditions. To clarify this, we measured the growth traits of clones over several years at multiple sites to evaluate the effects of genetics and environment on growth. The results indicate that growth traits exhibit significant genetic differences and high repeatability, and the significant G × E interaction highlights the importance of site-specific tree selection. Correlation and regression analysis indicated that MCMT was positively correlated with DBH, whereas DD < 18 was negatively correlated with DBH. TD and CMD showed positive correlations with height and volume. Multivariate regression trees (MRT) analysis showed that clones thrived under specific conditions: TD > 26.65 °C with MCMT > 0.1 °C and CMD > 520.5. Mantel analysis results indicated that TD is the main factor driving the G × E of DBH. To identify clones well-suited for targeted cultivation and stability in various regions, we estimated BLUP values for clone growth and applied BLUP-GGE to assess the yield and stability of 5-year height, 9-year DBH, and 5-year volume. Clone 1-1 was selected for its high and stable DBH, with a 6.22% genetic gain. Clone 22-03 was selected for its high and stable volume, with a 12.11% gain. These elite clones are anticipated to boost C. bungei plantation productivity and are likely to be cultivated and promoted across multiple regions.