414
15.6.2 Provenance Tests in Argentina and Genetic Variation
of Quantitative Traits
Observation of trees in even-aged natural stands or plantations reveals large differences among individual size, stem straightness, growth phenology, pest and disease
tolerance, and other relevant traits. If only a small proportion of these differences
are under genetic control, the extent of genetic variation for quantitative traits must
be considered (Zobel and Talbert 1984). Knowledge of quantitative genetic variation plays a central role since breeding programs are conducted based on information provided by provenance trials (White et al. 2007).
In Argentina, during the 1970s, given the initial importance of A. angustifolia
plantations, INTA initiated studies to evaluate the behavior of 32 provenances from
the southern states of Brazil and 3 local provenances from Argentina. Fahler (1981)
studied the variation between and within those 35 provenances of A. angustifolia,
up to the age of 8 years by means of two trials. They were installed in 1972, one in
Puerto Libertad (25° 55′ 48″ S, 54° 30′ 4″ W, 290 m asl), with all 35 provenances,
and the other in San Vicente (26° 55′ 28″ S, 54° 25′ 50,6″ W, 534 m asl), with 31
provenances. Seed collection intended to sample most of the natural range, considering minimum distances between provenances (50 km) and trees within provenances (50 m). In both trials, provenances were represented by 10 open pollinated
families, and, in all cases, seeds were collected in natural stands. The experimental
design was compact family blocks with four individuals per family, 10 families per
provenance, and four replicates. The plantation frame was 3.5 × 3.5 m, which
allowed the study of genetic materials with low levels of competition between trees
up to the 8 years of age and without needing thinning.
The main results of these trials were the following:
– Significant differences between provenances were shown for total height at the
first year of planting and for diameter and volume from the fourth year in San
Vicente and from the fifth year in Puerto Libertad. The heights of the provenances were markedly homogenous. In contrast, the diameters were different
from each other, and the productivity measured as individual tree volume was
much more sensitive to detect the differences between provenances.
– In both trials, the partition of the total variance in genetic and environmental
variance showed that in all cases, the genetic effects, due to provenances, were
those with the greatest participation in the observed phenotypic variation. For
volume, between 59% and 67% of the variation was explained by the “provenance” factor.
– No genotype-environment interaction was detected. In both trials, the provenances located to the west of natural dispersal area of A. angustifolia were those
with the best behavior, while those from the east were the ones with the lowest
growth. Spearman correlation coefficients between sites for 31 provenances
common to both trials reached values of 0.83, 0.88, and 0.87 for total height,
diameter, and individual tree volume, respectively.
M. E. Gauchat et al.
15.6.2 Provenance Tests in Argentina and Genetic Variation
of Quantitative Traits
Observation of trees in even-aged natural stands or plantations reveals large differences among individual size, stem straightness, growth phenology, pest and disease
tolerance, and other relevant traits. If only a small proportion of these differences
are under genetic control, the extent of genetic variation for quantitative traits must
be considered (Zobel and Talbert 1984). Knowledge of quantitative genetic variation plays a central role since breeding programs are conducted based on information provided by provenance trials (White et al. 2007).
In Argentina, during the 1970s, given the initial importance of A. angustifolia
plantations, INTA initiated studies to evaluate the behavior of 32 provenances from
the southern states of Brazil and 3 local provenances from Argentina. Fahler (1981)
studied the variation between and within those 35 provenances of A. angustifolia,
up to the age of 8 years by means of two trials. They were installed in 1972, one in
Puerto Libertad (25° 55′ 48″ S, 54° 30′ 4″ W, 290 m asl), with all 35 provenances,
and the other in San Vicente (26° 55′ 28″ S, 54° 25′ 50,6″ W, 534 m asl), with 31
provenances. Seed collection intended to sample most of the natural range, considering minimum distances between provenances (50 km) and trees within provenances (50 m). In both trials, provenances were represented by 10 open pollinated
families, and, in all cases, seeds were collected in natural stands. The experimental
design was compact family blocks with four individuals per family, 10 families per
provenance, and four replicates. The plantation frame was 3.5 × 3.5 m, which
allowed the study of genetic materials with low levels of competition between trees
up to the 8 years of age and without needing thinning.
The main results of these trials were the following:
– Significant differences between provenances were shown for total height at the
first year of planting and for diameter and volume from the fourth year in San
Vicente and from the fifth year in Puerto Libertad. The heights of the provenances were markedly homogenous. In contrast, the diameters were different
from each other, and the productivity measured as individual tree volume was
much more sensitive to detect the differences between provenances.
– In both trials, the partition of the total variance in genetic and environmental
variance showed that in all cases, the genetic effects, due to provenances, were
those with the greatest participation in the observed phenotypic variation. For
volume, between 59% and 67% of the variation was explained by the “provenance” factor.
– No genotype-environment interaction was detected. In both trials, the provenances located to the west of natural dispersal area of A. angustifolia were those
with the best behavior, while those from the east were the ones with the lowest
growth. Spearman correlation coefficients between sites for 31 provenances
common to both trials reached values of 0.83, 0.88, and 0.87 for total height,
diameter, and individual tree volume, respectively.
M. E. Gauchat et al.