Genetic Characte Of Families In The2^nd Eucalyptus Urophylla Seedlings

Eucalyptus urophylla is a major timber species in southern China, fast growth, wide application and strongly adapted; it possesses a very important position in the forestry production.In order to realize the potential of Eucalyptus urophylla for solid wood products and realize the orientated breeding, different families of the2nd Eucalyptus urophylla seedlings in Dongmen Forestry Farm in Guangxi were studied. The three characteristics of Eucalyptus urophylla were measured, and the variations among them were analyzed.According to the survey data of height, breast diameter-height and volume growth of at age of3,4and5.Through modem breeding theory and quantitative genetic analysis to estimate genetic parameter and genetic gain; provide theoretical basis to genetic breeding of advanced generation for Eucalyptus urophylla. The main conclusions are as follows:1. ANOVA showed that there were extremely significant differences among families in height, breast diameter-height, volume and different years in each traits, which demonstrate that magnitude of genetic variation possessed among families and so have certain selection potential.2. There was a genetic thinning in seed orchard when its average breast diameter-height was15.73cm in2012. The average breast diameter-height, thinning intensity and average genetic gain was16.46cm,45.21%and6.58%in the age of5after genetic thinning. The result showed the genetic thinning are relatively reasonable.3. Compared with height and breast diameter-height, more variation existed for volume growth and the coefficient of variation was60%, suggesting a wide base for choice; Repeatability of height, breast diameter-height and volume among families in these three years between0.39and0.55, it indicated that the repeatability value were under moderate control (0.46to0.51) at the age of4and5.4. The height, breast diameter-height and volume growth at the age of3,4and5of Eucalyptus urophylla reached a significant level, and each genetic correlation coefficient reached8801、0.9524and0.9987, which shows that a close relationship among families3traits. In addition, the genetic correlation coefficient of breast diameter-height was bigger than the height; it means that the genetic stability of breast diameter-height is higher than height.5. Individual and family heritability of three traits were estimated respectively at the age of3,4and5.Relatively low values of heritability were estimated from3years age; The heritability of all traits at the age of4was the highest one; the heritability at the age of5was between3and4. Family heritability of height, breast diameter-height and volume growth was0.3476-0.4722,0.3621-0.4831、0.3701-0.4814; And the individual heritability of three traits was0.3408-0.4605、0.3538-0.3617、0.3693-0.4841. The results indicated that low genetic control for these3growth traits were existed. Compared with individual heritability, family heritability suggested a wider base for choice.6. Using height, breast diameter-height and volume growth3traits,45families are selected out. And there were54.00%families of the total higher than the average values of phenotype and breeding. These results showed that most of the families in the Eucalyptus urophylla orchard had ideal genetic properties. The genetic improvement to the plus trees within superior family and the superior families can produces higher genetic gains.7. The nutrient concentrations of the2nd Eucalyptus urophylla seedlings in the various organs of such a tree are in the following order:leaves> branch> root> stem (at the age of3and4); leaves> root> stem> branch (at the age of5). According to the distribution of nutrient elements at age of4and5in different organs of such a tree are in the following order:N>K>Ca>P>Mg. Single plant biomass of Eucalyptus urophylla increases with the stand age, it reached89.51kg at five stand ages which are higher than the reported results. The biomass of stem in different periods were higher than other three organs, the proportion of the total biomass were greater than55%. The annual growth rate and annual increment of stem were higher than the branch and root, though the annual growth rate and annual increment of leaves were the lowest one.