Genotypic Evaluation And Early Selection Of Larix Clones

Larch (Larix Spp) is becoming the preferred coniferous in northern China and sub-tropicalalpine region. Clonal forestry is in the advanced stage of the development of intensiveindustrial forestry. Strengthening the research of early selection and genetic improvement forlarch, emphasising clonal breeding, cultivating more new varieties and raising the yield perhectare have a important influence on the progress of clonal forestry for larch. In this thesis,Larix kaempferi clonal trial in Henan Province planted in1998and L.kaempferi and its hybridclonal trial in Liaoning Province planted in2006were researched for genetic variation ofgrowth, wood and phenological traits, age-age correlations, efficiencies of early selection andmultiple-traits selection for growth and wood traits, the application prospect on applyingnondestructive testing technology in wood property breeding. In the end, the rooting–phenology–growth–wood level4breeding program was raised. The major conclusions wereto:Genetic variation and early selection for growth traitsIn this study, a nonlinear mixed model by using Richards growth function as basic modelwas constructed to fit the relationship for first-hand data of growth traits of80L.kaempfericlones on age. The fitting data of growth traits of80clones were measured periodically fromage2to age15. The genetic variation among clones, age-age correlations, and age trends ingenetic parameters for growth traits were analyzed. Variant analysis revealed that tree height(HGT) and diameter at breast (DBH) were significant (1%level) among clones at every ages.The clonal repeatability of growth traits varied year-by-year, reaching the highest levels atdifferent ages for different traits (0.77at age2for HGT,0.70at age5for DBH and0.66at age8for volume, respectively). The age-age genetic correlations ranged from0.904to1.000forHGT, and from0943to1.000for DBH. DBH at different ages was more genetically correlatedto volume-15than HGT. With the estimates of efficiencies of early selection, the recommendation from present study was that the optimum age of early selection was age2forHGT and age5for DBH.Genetic variation and early selection for wood traitsAccording to the growth traits to select20representative L.kaempferi clones, and woodtraits of the20clones were measured periodically from age4to age15. The radical variationpatterns, genetic variation among clones, age-age correlations, and age trends in geneticparameters for wood quality traits were analyzed. The results showed that the radical variationpatterns for different wood traits were not the same, as microfibrillar angle decreased withageing, and modulus of elasticity increased with ageing. The clonal repeatability of woodquality traits increased with aging before age9, and after age9, most wood quality traitsremained fairly constant or decreased steadily. The stability of the curve of clonal repeatabilityfor microfibril angle was much better than the other traits. The variation tendencies with agingof age-age genetic correlations for different wood traits were different, as microfibril angle wasincreased at early stage and then tended to be stable, and modulus of elasticity increased slowlywith ageing. After age6, phenotypic correlations were generally lower than correspondinggenetic correlations estimates for all wood quality traits. With the estimates of efficiencies ofearly selection, early age selection for wood density could be effective from age5to6, and age9-10for wall thickness to lumen area, microfibrillar angle and modulus of elasticity.The correlations between nondestructive testing traits and wood traits by using Pilodynand microsecond were studied, and the results showed that there were significant negativecorrelations between Pilodyn penetration of south direction, north direction (Ps, Pn) and ringdensity (RD), early wood density (ED), ring wall thickness to lumen area (RT/D) and earlywood wall thickness to lumen area (ET/D). The stress wave velocity (SWV) had significantnegative correlations with ring microfibrillar angle (RMFA), early wood microfibrillar angle(EMFA) and latewood microfibrillar angle (LMFA), but had significant positive correlationswith ring modulus of elasticity (RMOE), early wood modulus of elasticity (EMOE) andlatewood modulus of elasticity (LMOE). Linear regression equations between nondestructive testing traits and corresponding wood properties were constituted, and the results showed thatlinear regression correlations between nondestructive testing traits and corresponding woodproperties were significant (P＜0.0001), indicating that it was feasible and effective toconstitute the linear regression equations of nondestructive testing traits to predict woodproperties.Genetic variation and early selection for phenological traitsTwo years old phenological traits after afforestation of75L.kaempferi and its hybridclones were observed and measured. The results showed that the phenological phases of thehybid clones by crossing L.kaempferi as female parent behaved matroclinous inheritance.Variance analysis, principal components analysis and correlation analysis (simple correlationanalysis and canonical correlation analysis) were respectively used for analyzing phenologicalvariation among L.kaempferi and its hybrid clones, phenological type classification ofL.kaempferi and its hybrid clones and relationship of growth and phenological factors. Theresults showed that all the phenological phases were significantly different among clones.Seventy-five clones divided into four phenological types according to the result of principalcomponents analysis. There were weak negative correlations between spring phenologicalfactors and growth, while top bud formation, top bud fully formation and growth period hadstrongly positive correlations with growth. Leafing for branch、leafing extremely for mainleader, top bud formation and top bud fully formation could well forecast the performance ofvolume at age7, and these phenological factors should be considered seriously in earlyselection.Multiple-traits selection for growth and wood traitsThe phenotypic and genetic correlations among growth and wood quality properties forfifteen years old of20L.kaempferi clones were analyzed, and the results showed that therelationships among traits were complicated, they might be promoted each other, or might alsobe restricted each other, therefore it is important to take a appropriate breeding procedure according to the main breeding traits so as to optimize the comprehensive selection effects. Theresults of the relationship between the control traits and volume with path analysis methodshowed that the interactive effect among HGT (height), DBH (diameter), RMFA (ringmicrofibrillar angle) and LMOE (latewood modulus of elasticity), and the direct effect of DBHand LMOE played very important role in controlling volume, which reflected that HGT, DBH,RMFA and LMOE became main affecting factors of volume. The result of multiple-traitsselection showed that clone27had the best performing, as the genetic gain of height, diameter,ring density, ring wall thickness to lumen area, ring microfibrillar angle and ring modulus ofelasticity were20.36%,33.76%,2.06%,-3.65%,-5.62%and0.79%, respectively.