Pw. Volker et al., GENETIC VARIANCES AND COVARIANCES FOR FROST TOLERANCE IN EUCALYPTUS-GLOBULUS AND EUCALYPTUS-NITENS, Silvae Genetica, 43(5-6), 1994, pp. 366-372
Controlled- and open-pollinated families of Eucalyptus globulus subsp.
globulus (referred to here as E. globulus) and E. nitens, were tested
for frost resistance at 3 test temperatures (-5.5 degrees C, -7.0 deg
rees C and -8.5 degrees C) using the electrical conductivity method. A
dditive, dominance and error variance and covariances were estimated u
sing a derivative-free restricted maximum likelihood (DFREML) procedur
e and heritabilities, genetic and phenotypic correlations were calcula
ted. E. nitens was more frost tolerant than E. globulus, the former be
ing largely undamaged at -8.5 degrees C. E. globulus control-pollinate
d material (GCP) was tolerant to -7.5 degrees C but was severely damag
ed at -8.5 degrees C. Open-pollinated E. globulus from both seed orcha
rds (GSOP) and natural stands (GOP) was severely damaged at -7.0 degre
es C with the 50% damage criteria probably met at about -6.0 degrees C
. Heritabilities were moderate to high for both species, ranging from
0.29 to 0.50 for GCP and 0.23 to 0.44 for E. nitens control-pollinated
material (NCP). It is suggested that estimates of heritability from E
. globulus open-pollinated families from native stands (GOP), with val
ues ranging from 0.53 to 0.61, are over-estimated due to the effects o
f selfing and neighbourhood inbreeding. Estimates of heritability for
open-pollinated families from seed orchards in both species (GSOP and
NSOP) were similar to corresponding control-pollinated families (GCP a
nd NCP, respectively) suggesting that removal of selfing and other inb
reeding effects have occurred. Genetic correlations between relative c
onductivity at different temperatures were high, suggesting the same g
enes are involved despite differing levels of damage.