Combining Ability Analysis And Genetic Parameters Estimation Under A Two-level Diallel Cross Experiment On Chinese Fir

In this thesis, the combining ability, heterosis, correlation between growth traits and wood properties and comprehensive selection index were studied based on a two-level diallel cross experiment of Cunninghamia lanceolata(lamb.)Hook, with a, which had 90 crosses and 23 years genetic testing. The genetic testing was planted on a genetic testing on YangKou Forest Farm, Fujian province in 1986. The main results were as follows:1. The result of combining ability analysis shown that, the total combining ability of 2×3 and 3×4 provenance crosses were ranked at the first three during in the 23 years genetic testing on the three growth traits;2×4 provenance cross was the best in the 23 years genetic testing in DBH; 2(4)×3(8) individual cross was the best in the 23 years genetic testing on the three growth traits.2. The heterosis on growth traits were dominated mainly by the effect of the cross Iik×Ijl(C) , and the SCA was the second and GCA was minimum in this experiment, based on the annual variation of heterosis among different provenance crosses and individuals crosses on growth traits, and the correlation between the heterosis and different combining abilities. On wood properties traits, correlation between the heterosis and different combining abilities, we found that the heterosis control mode of the red-colored heartwood ratio, eccentricity and basic density's were similar to the growth traits; The microfibril angle's heterosis mainly depend on the female parent's GCA of the provenance.3. There are highly significant correlations among any two of the three growth traits, the correlation coefficients were between 0.60503 and 0.97701. The correlation coefficient between DBH and volume was greater than that between height and volume in the same age of stand, and all of the correlation coefficients between DBH and volume were greater than 0.95. There are highly significant correlations among any two of the ages of stand on any one of the three growth traits.4. Single trait selection and genetic parameters estimation were conducted for each trait. Superior crosses between provenance and individuals with 10% elected rate for growth traits were selected, and the genetic gain of volume was estimated to be 28.04% and 23.07%, the genetic gain for height and DBH was estimated to be 5.38%¹1.32%; The genetic gain of eccentricity, the highest in the wood properties traits, was estimated to be 12.71% and 8.77%, and the genetic gain of microfibril angle was second, estimated to be 7.45% and 5.57%, the genetic gain of basic density was third, estimated to be 6.68% and 1.78%, the genetic gain of red-colored heartwood ratio was the minimum, estimated to be 0.60% and 1.63%. 5. A comprehensive selection index equation constructed with 23a's volume, red-colored heartwood, eccentricity, basic density and microfibril angle: I =0.287x₁+0.292x₂-0.803x₃-35.462x₄-0.917x₅ The estimation accuracy of the comprehensive selection index was 0.4766.6. There were nine superior individual crosses with 10%-elected rate according to the comprehensive selection index, and then select two superior single trees from every one of the nine crosses according to the comprehensive selection index, finally, elect twenty super single trees from the experimental forest single trees according to the comprehensive selection index.