Abstract:

Two groups of filial generation derived from 2 different Pinus massoniana completediallel cross were analyzed. Results showed that general combining ability(GCA), specific combining ability(SCA) and reciprocal effects were significant for some growth traits including height, DBH and volume index. The heredity of these growth traits was controlled by both additive and non_additive genes, with the non_additive genes playing a dominant role. The epistatic effect was greater in groupsⅠ(crossed in 1992) in comparison with groupⅡ(crossed in 1993). The SCA of P. massoniana growth traits was significantly greater than GCA, which would be due to different geographical provenances of parents and an indirect pre_selection undergone by GCA. Inbreeding depression was commonly observed for P. massoniana growth traits, and the extent of inbreeding depression was -17.8%～-18.4%,-23.3%～-27.7% and-44.3%～-50.6% for height, DBH and volume index respectively. It was observed that parents with small GCA value exhibited greater extent of inbreeding depression. Huge differences in hybrid vigor of different crosses were observed, and the difference between original cross and reciprocal cross was not significant. Based on volume index, ten fine crosses were selected from each of the two groups, and the average increment of volume index was 59.41% and 41.76% respectively in comparison with the average of testing groups, and was 100.58% and 74.61% in comparison with local commercial variety.

Key words: Pinus massoniana, complete diallel cross, combining ability, heterosis, selfing effects