Comprehensive selection of growth and stem form of superior paulownia clones in the hilly region of southern China

To address the problem of lacking superior Paulownia spp. clones in the hilly region of southern China, the study was carried out with 5-years-old clonal test plantation contained 24 Paulownia spp. clones. The genetic parameter estimations of 4 growth traits including DBH(D_1.3), height of the trunk(H_t), total volume(V_t) and ratio of height of extened trunk to original trunk (H₁/H₀), and 2 stem form traits including taper of the trunk (β) and form factor(f) of clones were conducted, and correlations among these traits were analyzed. Furthermore, evaluation and selection of Paulownia spp. clones were conducted by comprehensive selection index method. Results indicated that: significant differences existed in each of the 6 traits among these 24 clones. The repeatability of D_1.3 and V_t were 0.727 3 and 0.726 9, respectively. The repeatability of other four traits was smaller ranging from 0.201 8 to 0.383 7. There were very significantly positive phenotypic and genetic correlations among 4 growth traits, and there were negative phenotypic and genetic correlations between the two form traits (β and f). There were very significantly negative correlations between form factor and 4 growth traits. Genetic correlations between β and D_1.3, H_t, H₁/H₀ were significantly positive. Phenotypic correlations between β and D_1.3, V_t were significantly positive and positive, respectively. With a selection rate of 17%, clones 609, 204, 302 and 207 were selected as the superior clones by the method of comprehensive selection index. Compared with control, genetic and actual gains through these 4 clones were 3.93% and 5.40% for D_1.3, 5.75% and 16.75% for H_t, 21.84% and 30.04% for V_t, 13.18% and 34.35% for H₁/H₀, 5.72% and 28.34% for β, -0.45% and -1.62% for f, respectively.