19
and uncertain budget (Lindgren and Wei 2006). In return, the genetic gains achieved
are of course modest (Namkoong et al. 1980). However, the low-intensity breeding
strategy turns out to be the most effective for species with a low annual planting rate
(50–100 ha; White et al. 2007) and in particular for those used in active forest restoration programs, in which the interest for a high adaptability (and therefore high
genetic variability) prevails over the productive ones. Many times the main objective is the establishment of basic propagation materials (i.e., seed-producing areas,
seed stands, seed orchards) to ensure the provision of seeds for seedling production
(Kjaer et al. 2006), and only a low degree of genetic gain that simple ensures good
health and a not-inferior-to-the-average quality in the traits of interest.
In a low-intensity strategy, the improvement cycle is shorter, and the tools used
are fewer and more direct in effect than those applied in high input programs, which
use more complex technologies (complexity that depends on each species).
Recurrent mass selection and open pollination are the basis, and instead controlled
crosses and vegetative propagation are rarely used techniques. The selection of individuals for their phenotype can be carried out in natural populations or in existing
plantations if the species has begun to be domesticated. In the first case, individual
selection is recommended by the baseline method (Ledig 1974), while for the second, what is more effective is selecting by comparison with the neighbors.
In a low input program, the same physical population usually represents different
populations of the improvement cycle. The selected population (set of selected individuals in the base population) usually coincides with the breeding population (the
set of individuals that cross freely to start a new improvement cycle, thus regenerating genetic variability). In turn, it can also coincide with the propagation population, generally in the form of a seed orchard. Usually the breeding program does not
pass this stage, petering out in the first cycle. An evaluation of the progeny of the
selected population, even in the productive plantations, can lead to a genetic purification of the orchard already installed, achieving a 1.5 generation orchard.
Any breeding program should begin by identifying the breeding zones based on
environmental criteria (i.e., edaphoclimatic). Each breeding zone requires a particular program, which produces the propagation material to be used within it (White
et al. 2007). All accessible populations (natural or artificial) included within the
breeding area will represent the program’s base population. The next step will be the
identification and evaluation of provenances, which will require a wide and adequate sampling for the good representation of each one. In a low-intensity program,
a provenance trial will not only test the provenances best suited for the breeding
zone but may also constitute the base population for the next generation. In this
case, starting from trees that have already demonstrated their adaptation to artificial
management might be an advantage, and additionally the selection can be based on
the comparison between neighboring trees. However, conforming the selected population from these selections requires avoiding open pollination when propagating
selected trees (i.e., controlled pollination or vegetative propagation should be used),
since otherwise the progeny of the selected trees would include genes from
unselected individuals and provenances.
1 Native Forests Claim for Breeding in Argentina: General Concepts and Their State
and uncertain budget (Lindgren and Wei 2006). In return, the genetic gains achieved
are of course modest (Namkoong et al. 1980). However, the low-intensity breeding
strategy turns out to be the most effective for species with a low annual planting rate
(50–100 ha; White et al. 2007) and in particular for those used in active forest restoration programs, in which the interest for a high adaptability (and therefore high
genetic variability) prevails over the productive ones. Many times the main objective is the establishment of basic propagation materials (i.e., seed-producing areas,
seed stands, seed orchards) to ensure the provision of seeds for seedling production
(Kjaer et al. 2006), and only a low degree of genetic gain that simple ensures good
health and a not-inferior-to-the-average quality in the traits of interest.
In a low-intensity strategy, the improvement cycle is shorter, and the tools used
are fewer and more direct in effect than those applied in high input programs, which
use more complex technologies (complexity that depends on each species).
Recurrent mass selection and open pollination are the basis, and instead controlled
crosses and vegetative propagation are rarely used techniques. The selection of individuals for their phenotype can be carried out in natural populations or in existing
plantations if the species has begun to be domesticated. In the first case, individual
selection is recommended by the baseline method (Ledig 1974), while for the second, what is more effective is selecting by comparison with the neighbors.
In a low input program, the same physical population usually represents different
populations of the improvement cycle. The selected population (set of selected individuals in the base population) usually coincides with the breeding population (the
set of individuals that cross freely to start a new improvement cycle, thus regenerating genetic variability). In turn, it can also coincide with the propagation population, generally in the form of a seed orchard. Usually the breeding program does not
pass this stage, petering out in the first cycle. An evaluation of the progeny of the
selected population, even in the productive plantations, can lead to a genetic purification of the orchard already installed, achieving a 1.5 generation orchard.
Any breeding program should begin by identifying the breeding zones based on
environmental criteria (i.e., edaphoclimatic). Each breeding zone requires a particular program, which produces the propagation material to be used within it (White
et al. 2007). All accessible populations (natural or artificial) included within the
breeding area will represent the program’s base population. The next step will be the
identification and evaluation of provenances, which will require a wide and adequate sampling for the good representation of each one. In a low-intensity program,
a provenance trial will not only test the provenances best suited for the breeding
zone but may also constitute the base population for the next generation. In this
case, starting from trees that have already demonstrated their adaptation to artificial
management might be an advantage, and additionally the selection can be based on
the comparison between neighboring trees. However, conforming the selected population from these selections requires avoiding open pollination when propagating
selected trees (i.e., controlled pollination or vegetative propagation should be used),
since otherwise the progeny of the selected trees would include genes from
unselected individuals and provenances.
1 Native Forests Claim for Breeding in Argentina: General Concepts and Their State