Abstract:

This paper gave the results at age 7 from a complete-diallel cross among 6 Pinus massoniana clones from different seed sources. It was found that variances due to general combining ability (GCA) and specific combining ability (SCA) were significant for height, DBH, volume index, wood basic density and dry matter index. However, the dominant gene effect was predominant over the additive effect. Epistasis effect was varied with traits tested. Analysis of data revealed marked epistasis gene action for wood basic density. Inheritance pattern of growth and wood properties was found to be different from maize and Chinese Fir. The main reason for this seemed to be that the mating parents were from different seed sources and/or indirect selection on GCA of growth had been made for mating parents. There was usually selfing depression for growth traits. Selfing progeny from parents with smaller GCA seemed to reveal more significant depression. Heterosis between various cross combinations was greatly varied. As a whole, reciprocal crosses had similar heterosis. There were some but no obvious trend that the cross between parents with larger GCA could produce more heterosis in volume increment and dry matter accumulation. Eight superior cross combinations for pulp wood were screened based on dry matter index.

Key words: Pinus massoniana, Pulpwood, Complete-diallel cross, Combining ability, Heterosis