Genetic And Environmental Effects Of Eucalypt Hybrid Clones On Pulpwood Traits

Eucalypt is one of the worldwide most important pulpwood tree species. Hybridization anduse clones as planting material are the important characteristics to tropical eucalypt breeding.Currently, systemic study on the effects of genetic, environment, interaction of genotype andenvironment on important eucalypt pulpwood traits is vey limited. To guide eucalypt breedingand the extension of superior varieties, This study used20eucalypt hybrid clones newly selectedor widely using as genetic material. The20clones belong to6different species or hybrids. Dataon their growth, wood properties and pulp and paper properties at closing to their rotation age(5.5-yrs)from4-5sites were used, systemic study on their genetic and environmental effectswere carried out. The main results are as below:There were significant genetic variations for all the important pulpwood traits studied onspecies (hybrids), hybrid combinations and individuals within combination levels. And, Therange of variance on growth traits (to250%) were significantly wider than that of wood qualitytraits and pulp and paper property traits (to20%). Hence,though repeatability of growth traits(30%-45%) were lower than those of wood quality traits (70%-85%), but its potential geneticgains through selection will be higher than those of wood quality traits.The between site variances on both growth traits and wood quality traits were all significant.But variances on growth traits (to35%) were much higher than that to wood quality traits (to4%).The between site differences to main wood chemical contents and pulp strength traits were bothinsignificant (1%-4%). Correlation analysis on all the pulpwood traits and environmentalfactors found that mean annual temperature,mean annual rainfall and soil organic contents werethe main factors significantly affecting growth. Soil grain sizes significantly affected barkthickness and some wood distillate contents.There were significant G×E interaction for growth traits and wood density. The G×Einteraction to fiber quality traits were insignificant. The significant G×E interaction weremainly on species (hybrid) level, the interactions on combinations within hybrid species leveland individuals within combination level were all insignificant.The study also showed that productivities of most of the studied clones were high. Thenewly selected clones' productivity were higher when comparing with the widely using clones.The best2clones can bring a more than60%genetic gain on volume and wood mass. But, thesignificant G×E interaction on clones should be noticed, it can cause genetic gain lose to all thetraits (The potential gain lose to stem volume is about4.0%).Through this study, We are strongly convinced that eucalypt pulpwood improvement shouldbe on hybrid parents (species) selection. Meanwhile, within hybrid combination selection (toselect proper individuals as the hybrid parents) should be made. Then, to select best individuals(clones) within superior combinations. Growth traits improvement is suggested to be thepriority, and then to consider of wood quality improvement. To avoid the gain lose caused byG×E interaction, superior variety selection should be conducted in different type of sites.