Abstract:

Objective: According on the study of growth characteristics at seedling stage of 8 half-sib families of Malania oleifera from 7 germplasm resources at different altitudes in Yunnan Province, the combined selection of families and individual plants was conducted, providing a theoretical basis for precise grading of seedlings, formulating the seedling cultivation measures and long-term breeding strategies of M. oleifera. Method: A sowing and seedling experiment was conducted with freely pollinated seeds that were collected from 8 superior M. oleifera plants with good shape and stable fruit setting rate, at 7 different altitudes, to measure the growth, form quality, leaf traits of the half-sib family seedlings. The mathematical growth model optimization, membership function evaluation, cluster analysis, and analytic hierarchy process were used to evaluate growth characteristics at seedling stage of half-sib families of M. oleifera and complete the combined selection of families and individual plants. Result: During the measurement period, the growth of seedling height and ground diameter of 8 M. oleifera half-sib families derived from 7 different altitudes germplasm resources showed a“slow?fast?slow”growth rhythm. There was a significant difference in the net growth volume of seedling height and ground diameter among the half-sib families, with the minimum value of seedling height net growth volume of 0.98 cm, the maximum value of 13.07 cm, and the range of extreme difference of 12.09 cm, and the coefficient of variation ranged from 25.8% to 64.5%. The minimum value of ground diameter net growth volume was 0.33 mm, the maximum value was 1.87 mm, the extreme difference reached 1.54 mm, and the coefficient of variation ranged from 15.5% to 43.6%. There were differences in the beginning of rapid growth, the end of rapid growth and the rapid growth period among different families, thus the seedlings were able to be divided into three types of rapid growth seedlings during the early, middle and late stages, which accounted for 33.8%, 36.6% and 29.6% of the total seedlings, respectively. Among them, the seedlings of rapid growth at the ground diameter during the early, middle and late stages accounted for 81.7%, 12.7% and 4.2% of the total seedlings, respectively. Q-type clustering analysis clustered the seedlings into 3 classes at an euclidean distance of 7.97. Class I contains 21 individual plants with fast growth rate, average seedling height of 39.4 cm and average ground diameter of 6.86 mm; class Ⅱ contains 48 individual plants with moderate growth rate, average seedling height of 28.0 cm and average ground diameter of 6.36 mm; class Ⅲ contains 3 individual plants with slow growth rate, average seedling height of 15.9 cm and average ground diameter of 5.67 mm. In the hierarchical analysis, the cumulative total weight of seedling height, ground diameter, seedling index, crown width and leaf area was 0.756 0, which was the main preferred index for individual plants selection. Conclusion: The overall growth rhythm of half-sib family seedlings of M. oleifera from Yunnan Province shows allometric growth. According to the calculation of subordinative function value, the optimal mathematic model of growth is the Logistic model, the families F2, F7 and F12 are the best seedling height growth seedlings, families F23, F17 and F2 are the best ground diameter growth seedlings. According to the hierarchical analysis screening, F7-81-2, F7-81-3, F2-43-3, F16-133-3, F6-61-18, F2-43-3, F2-43-10 are the best individual plants.

Key words: half-sib family, Logistic, germplasm resources, membership function, AHP