Abstract:

The genetic characteristics and combining ability for growth,stem-straightness and wood density were estimated on 16 seven-year-old F₁ families derived from crossing with 4 female and 4 male parents of Pinus taeda×P. caribaea with the NC II mating design. Analysis of variance showed that there were significant differences(P<0.01) in growth and wood basic density among 16 crosses, and (P<0.05) in stem-straightness. The heritability (h²) analysis showed that family mean heritability of growth,stem-straightness and wood density for female parents was higher than that for male parents, while the mean h² for the full-sib families was in the middle of the parents heritability. The h² of growth was 0.292 3-0.469 9 for female parents, and 0.191 9-0.403 3 for male parents. The family mean and single tree h² of wood basic density for female parents was 0.176 4 and 0.034 6, respectively, and the single tree h² of stem-straightness for male and female parents was 0.162 7 and 0.098 3, respectively. The heritability of DBH and volume was increasing in the last 6 years while the heritability of tree height was decreasing. The analysis of genetic correlation showed that growth traits had positive correlation (|r_G| =0.467 2-0.351 6) with stem-form, and had a negative one(|r_G| =0.220 3-0.679 8) with wood basic density. The general combining ability (GCA) effect of male or female parents for growth traits and stem-straightness was significantly different, and their special combining ability (SCA) effect for wood basic density was significant. The effective value of combining ability for GCA and SCA was estimated and the better parents and hybrids were evaluated. The correlation between genetic background of the parents and genetic differences of the progenies was discussed.

Key words: Pinus taeda×, P. caribaea, growth traits, wood basic density, stem-straightness, heritability, combining ability