Analysis of the genetic effects of seed and seedling traits of Betula platyphylla in a 5×5 complete diallel cross design

Betula platyphylla is an important industrial wood species with fast growth, strong adaptability and good timber. The genetic parameters of its parents were estimated by analyzing F1 descendant for seed and seedling traits in order to select optimum parents for the second generation seed orchards of birch. Five parents of birch from Xiaobeihu (BH) of Ning'an County as well as Maoershan of Shangzhi County of Heilongjing Province were crossed by a 5 by 5 diallel cross design in 2003 and their hybrid seeds and seedlings were tested on thousand-grain-weight, germination percentage, germination viability, seedling height, and ground diameter. The results indicated that there were significant differences at the probability of 0.01 level in the characteristics of seed and growth traits among crossing combinations, and also in the general combining ability (GCA), specific combining ability (SCA) and reciprocal effects (REC) of thousand-grain-weight, germination percentage and germination viability of seed, SCA and REC of seedling height and ground diameter. Only at the 0.05 level of probability are there statistically significant differences in the GCA of seedling height, and the differences in GCA of the ground diameter of seedlings were not significant. M4×M1, BH3×BH2, M4×BH3, BH2×BH1 and BH2×M1 are superior cross combinations given the effects of GCA and SCA. Also M4 and BH3 are superior parents.