Genetic Characteristics Of Growth And Wood Properties In Hybrids Of Eucalyptus Urophylla And E.pellita

E.pellita and E.urophylla are commercially important Eucalypt species as their excellent performance in fast growth and environmental adaptability in China.Their hybrids also have outstanding advantages in fast growth and disease resistance.In recent years,their hybrids have been highly valued in new variaties developing and breeding theory study.But,most research on hybrids between E.pellita and E.urophylla mainly focus on growth traits.The genetic characteristics of stress resistance and wood properties are not adequately reported.Here,the characteristics of volume growth,disease resistanc,wood properties,veneer properties et al for1.5-year and 5-years hybrids between E.pellita and E.urophylla were studied,and the genetic parameters of interested traits were estimated.The genetic improvement potential of these hybrids were discussed,so as to provide scientific basis for development,utilization hybrids between E.pellita and E.urophylla.The main results are as follow:(1)The 1.5yr performance results of 3 taxa hybrids were ranked as E.urophylla×E.pellita>E.urophylla×E.grandis>E.urophylla×E.urophylla according to tree height,DBH,volume and survive rate.The significance of differences on tree height,DBH,volume and disease resistance index were at the level of P<0.0001.Tree height,DBH and volume of E.urophylla×E.pellita were 9.26 m,8.03 cm and 173.88 dm~3 respectively,which were 15.75%,11.68%and33.38%higher than those of E.urophylla×E.urophylla.The disease resistance index of E.urophylla×E.pellita along with that of E.urophylla×E.grandis(～4.0)were significantly higher than that of E.urophylla×E.urophylla(3.48).The difference of survive rate between hybrid types were at P<0.01 level significance,and E.urophylla×E.pellita was the highest(82%).The heritabilities of different hybrid types were different.E.urophylla×E.pellita’s hetitability on survive rate and disease resistance index were around 0.8 and those were the highest in the hybrid types.Heritabilities of its other traits were varied from 0.3 to 0.5,the value were in between to the other 2 hybrid types.The results showed that E.urophylla×E.pellita hybrids had significant advantages in early rapid growth and stress resistance and these traits were under moderate to strong genetic control.(2)Genetic analyse on growth,wood properties and log properties of 5-year hybrids(E.urophylla×E.pellita、E.pellita×E.urophylla、E.urophylla×E.grandis、E.urophylla×E.urophylla、E.pellita×E.pellita)showed that:DBH and volume of the hybrids were not significantly different from each other.But the difference on tree height and survive rate were significant.E.urophylla×E.pellita and E.urophylla×E.urophylla’s survive rate were all over 70%.Those were significantly higher than E.urophylla×E.grandis and E.pellita×E.urophylla’s 60%,E.pellita×E.pellita’s 41%.There were no significant differences in growth stress,elastic modulus and wood density measured on living trees between E.urophylla×E.pellita and other hybrids.For the wood properties on logs,the heartwood rate of E.pellita×E.urophylla and E.urophylla×E.pellita were 40.15%and38.47%.Were moderate value in all the species.The wood characters that E.urophylla×E.pellita had adventages include:less branching,higher roundness,lower bending,less cracking than other hybrids.The heritebilities of E.urophylla and E.pellita were mainly between0.05～0.27,only DBH had a heritability low as 0.05,while other traits’were between over 0.2.(3)The genetic characteristic of wood veneer recover rate and veneer quality traits of 5-year hybrids suggested that:There was no significant difference in the veneer recover rate.Compared with other hybrids,the hybrids of E.urophylla×E.pellita and E.pellita×E.urophylla had higher cracking,and the number and length of cracks were higher than those of other hybrids.E.urophylla×E.pellita and E.pellita×E.urophylla had about 5 crackings,while other species were 3～4.5.The average crack length of E.urophylla×E.pellita and E.pellita×E.urophylla hybrids were 15cm,while other hybrids’were 13 cm.The number of holes on veneer were significantly different between the species.With E.urophylla was the lowest and E.pellita was the highest,E.urophylla×E.pellita and E.pellita×E.urophylla were in between.Due to the complexity of veneer sampling and the limited data obtained,Heritability of veneer traits were not estimated.In conclusion,E.urophylla×E.pellita has significant advantages in early growth and stress resistance,and showed moderate performance in wood and timber properties and veneer recovery.The quality of its veneer were not significantly different from other hybrids,E.urophylla and E.pellita.