Analysis of genetic effects on growth traits in a 5×5 diallel cross of Betula platyphylla.

Tree height, diameter at breast height (DBH) and volume of fullsib progenies were measured using a 5× 5 diallel cross of four local strains of Betula platyphylla (B1, B2, B3 and B4) and one European strain of B. pendula. The results indicated that height, DBH and volume among crossing progenies differed significantly. General and specific combining ability (GCA and SCA), and reciprocal effects (REC) of the growth traits also differed significantly. Based on the estimation of growth amount, GCA, SCA and REC of crossing progenies, we selected B1, B4 and B3 as the best parent strain, female parent strain and male parent strain, respectively. For B1, its GCA for height, DBH and volume were 0.126 3, 1.136 7 and 0009 1, respectively. The height, DBH and volume of B1 hybrid progeny were 3.37%, 5.05% and 12.18% higher, respectively, than the average progeny performance. B1×B3, OB×B1 and B4×B3 were superior crosses in a preliminary selection. The SCA for height, DBH and volume of B1×B3 was 0.091 0, 0.808 0 and 0.007 0, respectively. The height, DBH and volume of B1×B3 progeny were 13.11%, 21.21% and 55.76% higher, respectively, than the average progeny performance. The study provides a theoretical basis for the parent selection and the establishment of a second generation seed orchard for birch.