Genetic Variation Characteristics Of Growth And Wind Resistance Of Eucalyptus Pellita In Two Generations

Eucalyptus pellita is one of the most important species for high quality timber and pulpwood production.It's main planting area in China is in the typhoon frequent South China.It is important to study the genetic characteristics of growth and typhoon resistance traits and its change tendency when generations advanced.The testing trials of this study were located in Suixi County,Guangdong Province,China.The genetic material of first generation include 14 provenances/244 families from Australia,Indonesia and Papua New Guinea.That of the second generation include 83 excellent individuals' progeny(from 12 provenances)that were collected from the first generation trait.In this study,the genetic variation characteristics were studied and genetic parameters estimated on the two consecutive generations.Comparation of the genetic characteristics in the two generations were made.The studied traits include: 1-year,2-year,3-year and 10-year growth traits;3-year(the 1st generation)and 2-year(the 2nd generation)wind resistance traits and 8-year(the 1st generation)and 10-year(the 2nd generation)wood density.The main results are:(1)Genetic variation of growth traits: There were no significant difference between the origins of two generations for all the studied growth traits,the difference among provenances and families of growth traits were significant except that for the 10-year height in the first generation.It was indicated that the two generations' Eucalyptus pellita are present abundant variation in the provenances and families.The overall average of height of 1-year and 2-year,was 2.56 m and 8.3 m in the second generation,which were higher than the first generation's 1.27 m and 7.66 m.But the DBH and volume difference were smaller.The 3-year height,DBH and volume in the first generation was 10.83 m,9.82 cm and 0.038 m3,and those of the second generation were 9.62 m,8.61 cm and 0.022 m3.But at the age of 10,the first generation showed dominant performance advantage because of heavy thinning.The growth of both the two generations' Eucalyptus pellita were under medium level genetic controlled.The heritabilities of growth traits were between 0.15~0.39 in the first generation,while the second generation had a slight decrease,and its range was 0.08~0.21.When 200 superior individuals were selected as the samples for genetic gain estimation.The results found: The genetic gain of height in two generations will be 11.77% and 3.98%(2-year-old),6.41% and 2.98%(3-year-old),1.92% and 6.17%(10-year-old),respectively.The genetic gain of volume of the 3 ages were 34.66% and 13.63%,29.43% and 5.69%,9.20% and 15.50%,respectively.The genetic gain of DBH was not significantly different at 3-year-old and 10-year-old,and genetic gain of the two generations were 5.86 and 5.69,5.53 and 5.24,respectively.The genetic gain of each growth trait decreased with the increase of ages in the first generation,while the second generation showed an opposite trend.(2)Genetic variation of wind resistance: There were significant differences in the wind resistance of the two generations between origins,provenances and families.In the first generation,the wind resistance of the Australian provenances had higher wind resistance,typhoon resistance index was 4.5 and that of Papua New Guinea provenances was only 2.9.However,in the second generation,the wind resistance of Papua New Guinea was significantly improved,the wind resistance index of the AUS and PNG origin were 4.3 and 3.9,respectively.The origin difference is smaller than the first generation's.At the provenance and family level,the second generation all showed a better resistance to typhoons.The overall 3-year preservation rate of 2nd generation was 3 times that of the 1st generation,and the wind resistance index increased from 1st generation's 3.99 to 2nd generation's 4.25.The heritability of wind resistance index of the two generations were 0.36 and 0.24,respectively.The genetic gain of the two generations were not changed when the selection rate was 0 ~ 57%,but the genetic gain of the volume will significantly reduce when the selection rate increased.There was a significant negative correlation between the wind resistance traits and the growth traits.(3)Genetic variation of wood density: there were no significant difference between the two generations' wood density at both origin and provenance level,but there was significant difference between families.The average wood density of the first generation was 514.3 kg/m3,and the second generation was 504.8 kg/m3.And in two generations,the wood density of Papua New Guinea provenances is lower than that of Australian provenances.The variation range of the wood density in the first generation was 475.4 kg/m3~547.2 kg/m3,and the second generation was 454.7 kg/m3 ~ 627.8 kg/m3.The difference of provenance means were 62.7 kg/m3 and 165.7 kg/m3 in the two generations,respectively.The maximum wood density value on family level in 2nd generation is significantly higher,and the minimum value was significantly lower.The inter-family variation were also enlarged.The heritability of wood density of the two generations were 0.54 and 0.63,respectively,which showed high level genetic control.Therefore,to make selections on both family and individual level will both expected to obtain high genetic gain.Wood density of the first generation were negatively correlated with growth traits;The second generation showed positive correlations,though the correlation were not significant.In summary,In the growth of the two consecutive generations,the provenance and familie level genetic variation in 4 ages were all significant.The wind resistance had significant genetic variation between provenances and families,and overall wind resistance of the second generation was significantly improved when comparing with the first generation.The basic wood density was significant varied between family and individual levels.The average wood density in the second generation is lower than the first generation,but the variation range between provenances and families are larger than the first generation.Therefore,the fast-growing,wind resistance and wood density traits of Eucalyptus pellita in both of the generations have great potential to improve.Considering the variation characteristics of growth traits,wind resistance and wood basic density,the selection of excellent parents for high-generation and make of breeding strategy for higher generation of E.pellita should all make a reference on the results.