Genetic Variation and Mid- term Selection of Second Generation Eucalyptus tereticornis
In order to select elite families and superior individuals with high genetic gains,the growth traits and genetic evaluation of the second generation of 4.4-year-old Eucalyptus tereticornis were tested. Results showed that there were extremely significant differences in D,tree height (H),and volume (V) among 103 families. The family heritability of D,H,and V was bigger than individual heritability,both of which were above the 0.5 level, indicating that family was under the control of higher genetic intensity and single plant was under the moderate genetic intensity control. Exponential equations for the selection of E. tereticornis fami-lies and individual plants were constructed based on D,H and V,and 14 elite families of E. tereticornis were selected with a standard deviation level,and the selection intensity was 13.59%. The average genetic gains of D,Hand Vin selected elite families reached 30.20%, 20.55%, and 74.51%, respectively. The optimal families were Y19, Y67, Y64. 52 superior individuals of E. tereticornis were selected by using two standard deviation intensity levels,and the selection rate was 3.12%. Selected individuals mainly distributed in 36 fam-ilies,among which 50%distributed in excellent families,and the selection effect was obvious.
Eucalyptus tereticornisgenetic variationgenetic gain