Stability analysis and comprehensive selection of elite clones of Catalpa bungei based on wood growth and hydraulic architecture in two sites with different rainfall

Drought is a negative factor limiting tree growth and wood productivity of Catalpa bungei, a native species of the Catalpa genus in China that is characterized by high-quality timber and significant economic value. In the present study, stability analysis and comprehensive selection of elite clones of C. bungei were conducted based on gas exchange, wood growth, and hydraulic architecture at two sites with different rainfall levels. Tree growth and wood productivity of C. bungei were largely inhibited by rainfall shortage and the incongruity between rainfall and temperature. Some clones showed prominent wood productivity and fine wood properties at the Heze site, which experienced water deficit and seasonal drought. The high clone repeatability (R > 0.65) of these traits implies great potential for selecting drought-adaptive varieties. Specific clones with high stability in wood productivity and basic wood properties were selected based on BLUP-GGE biplot analysis. Elite clones (2–8, 2–6, 19–01, 1–3, 6–7, 008–1, and 22–03) with favorite wood growth and hydraulic safety were selected based on comprehensive assessment, and these clones are proposed for extension and cultivation in climate regions with limited rainfall. The outstanding growth performance of elite clones was attributed to their larger leaf area and great photosynthesis capacity per plant, rather than to a high photosynthetic rate per unit leaf area. Most of the elite clones exhibited timely adjustments in hydraulic architecture (vessel diameter and vessel density) between the drought season and the rainy season, which contributed to an effective trade-off between wood growth and hydraulic safety.