Selection On High-yielding Hybrid Clones Of Eucalyptus Urophvlla×E. Tereticornis For Pulpwood Plantation

Eucalyptus urophylla×E. tereticornis hybrids were researched by Eucalyptus introduction, breeding and improvement in Leizhou Forestry bureau since1980s. By the investigation and analysis data, different E. urophylla×E. tereticornis clones have been studied on growth, wood properties，wood chemical component，pulping properties and resistant level for the excellent clones selection. The objection of all the research is to findmore better clones for sustainable breeding, cultivation, popularization and applicationconstantly which can improve afforestation efficiency of ecology, society and economy.The main conclusions are as follows:（1）The best3clones are LL70, LL53and A01in the135clones according to the mean AHCI value（average growth increment per hectare in one year）, and the value are37.64,33.62and30.79m³.hm^-2.a^-1, respectively. The repeatablity of all growth traits of135clones are0.8569⁰.8932, the genetic gain can reach13.89%⁷7.46%and the excellent clones can be selected including of LL70, LL53, A01, LH5, LL244,BP1, LL246, LL241, LL59, LL123, LH4, JJ53, LH1and LL120at10%selected rate,and it indicated that the repeatablity value are very high and the growth traits have been affected sorely by the parents. The repeatablity of all growth traits of41E. urophylla×E. tereticornis clones are0.8344⁰.9380and the genetic gain can reach14.77%⁵3.28%at12%selected rate. The sites analysis results indicated that Tangjia and Shiling are better than Beipo among3forestry farm according to the clone growth level. According to the effect of adaptability and stability analysis of clones in3-site trial,41clones could be classified into4groups that had been named high-yeild and stable-growing group including of19clones, high-yeild and unstable-growing group including of5clones, low-yeild and stable-growing group including of7clones, low-yeild and unstable-growing group including of11clones. High-yeild and stable-growing group was fit for excellent-family selection and generalization.（2）Average BR （bark rate%） is15.24%of all135clones in wood properties; Average wood base density is482kg.m^-3of44clones; The3best clones of FL （Fiber length） value are A16, A07and A18in11clones, and the3best clones of FL/W （fiber length/width） value is are A16, A15and A18. The3best clones are A18, A07andA01according to the value of AFC%（Arithmetic fiber content/%）. Synthesis analysisaccording to the wood properities indicated that A18, A15and A01are the best clonesin11clones.（3）Average value of ash%, HWE%（hot water extractive%）,1%NaOH extracitve%, benzene ethanol extractive%, pentosan content％, holocellulose content％and lignincontent％are0.52%、2.09%、12.32%、0.73%、20.84%、82.74%�'�24.66%according tothe wood chemical component and pulping properties of11E. clones, respectivly. By traits value of taxis of11clones coordinate assessment the3most excellent clones areLL67, A16and A20，but the clontrol clone ZU6is the5thtaxis in11clones.（4）With two kinds clones of Eucalyptus urophylla×E. tereticornis as the experimental materials including of LH1and U6, basic density, fiber morphology and chemical components were determined and analyzed to study the relatioship between wood properties and tree age. The results showed that the FL, FW（fiber width）, FL/W value, pulp yield%, tensile index and wood brightness%can improve with the ages. The valueof FL and FL/W are0.6⁰.8mm and34.4⁴2.4, and the LH1is higher than ZU6including of the properities of FL, FL/W, pulp yield%and tensile index at the same age.The value of E. holocellulose content%, tensile index and brightness is82%,64.5N.m.g-1and30%ISO respectively. With the increasing of tree age, basic density and holocellulose content%rises while ash%and1%NaOH extractive%drops. Basic density of U6and LH1of five years are about443kg.m^-3and474kg.m^-3respectively, which would be better for optimal output, little effects of impregnation. The ash%of U6and LH1is about0.5^-1.1%, Length-width ratio is lower than45, which would be harmful for strength properties of paper. With the comprehensive comparison of pulp yield and tensile strength between U6and LH1, pulping performance of the LH1is better than U6.（5）Synthesis analysis according to the wood properities, wood chemical matter content and pulping performance indicated that A15clone is the best clones in all11Eucalyptus urophylla×E. tereticornis clones for the2ndtaxis of wood properites, the4thtaxis of chemical matter content and pulping performance.（6）Comprehensive analysis the effect of wind-damaged of135clones indicated that resistant ability of11clones are higher than others, and those are LL81, LL79, LL90, LL92, LL60, BP17, LL53, LL91, LL77, LL61and LH3E. clones including of3Eucalyptus urophylla×E. tereticornis clones such as LL91, LL77and LH3. Average value of wind-damaged rate is7¹3.9%.（7）Average Mortality rate of77clones is0⁴1.7%because of Pseudomonas solanacearum infection, and there are15clones that mortality rate are0including of8Eucalyptus urophylla×E. tereticornis and4E. camaldulensis clones. All the15clones are A01, BP22, LH1, LH4, LL123, LL244, LL246, LL62, LL71, LL81, LL98, SH7, SX9,TJ29and ZU6. There are more relativity and same effects between Pseudomonas solanacearum influence and wind-damaged for E. clones, so synthesis analysis the effect ofwind-damaged and Pseudomonas solanacearum infection indicated that the clones if itis from parents of E. tereticornis and E. camaldulensis will have a strong resistant forthe2kinds of harms and an important exploitated value for breeding.（8）By the methods of coordinate assessment and synthetically membership functionto synthesis analysis the42clones traits including of growth, wood properites and chemical composition, there are5best clones to be selected respectively. The5best clones are LH5, LL53, LL70, LH4and LL59by coordinate assessment method, and the5best clones are LH5, LL70, LH4, LL53and LL59by synthetically membership function method. The control clone ZU6is the15thor18thtaxis among42clones respectively. Compare to the2methods, there are9same clones in the10best clones and thos e are LH5, LL53, LL70, LH4, LL59, LL91, LL67, LH3and LL81. Of the10best clones there are6Eucalyptus urophylla×E. tereticornis clones can be popularized and applicated in resistance breeding and clones propagation in future for those good traits.（9）Combinating of high wood yeild, better wood properites and stronger resistant, there are more better clones can be selected in production for afforestation in Southern China. If progeny can inheritance such forgoing better traits, the gene-resource values will improve E. industry for more efficiency of ecology, society and economy by geneticbase collection and continuous breeding.