474
among individuals. These results allowed the selection of trees, showing high stability at molecular and morphological level but conserving a percentage of variability,
based on high genetic distance individual criteria for selection. These trees will be
used in the Prosopis alba breeding.
In the case of Prosopis denudans, studies of genetic diversity and genetic structure of natural populations have been started in order to assist ecological restoration
and breeding programme (for biomass product) (Vivien Pentreath unpublished
data). It is a shrub (or small tree) of Patagonia adapted to the cold and semi-desert
steppe, thus showing tolerance to drought, salinity, alkalinity and cold. Neutral and
putative functional SSRs transferred from P. alba were used, revealing most of them
moderate to high degree of genetic diversity (e.g. average observed and expected
heterozygosities ranging from 0.324 to 0.732) and low genetic differentiation
between populations (F ST = 0.064). This work will be continued with more analyses
using molecular, morphometric and environmental data, in order to study the influence of the different factors on the genetic diversity of the species and to identify/
select better genotypes.
Among Nothofagus species, several studies have been carried out or started in
the last years based on the genomic resources and molecular markers developed by
high-throughput sequencing. Azpilicueta et al. (2016) using SSRs and Sanger
sequencing of nuclear Adh and ITS genome regions evaluated the taxonomic status
of Lagunas de Epulauquen population, the northernmost population of N. obliqua in
Argentina, which has been questioned due to its morphological, architectural and
genetic distinctiveness. The performed analysis revealed that individuals from this
population were closely related to other N. obliqua individuals, while the presumed
hybridization with N. alpina was not detected. This result supports the inclusion of
Lagunas de Epulauquen within Argentinean N. obliqua domestication and breeding
programmes, increasing the genetic diversity available for individual selection.
El Mujtar et al. (2017b) used six species-specific nuclear SSRs for the identification and classification of hybrids, in natural mixed forests of N. obliqua and
N. alpina, based on estimates of ancestry and interclass heterozygosity. Results
indicated that (1) introgressive hybridization occurs at a global rate of 7.8%; (2) F1
hybrids occur at a global rate of 3.8% and are fertile, as the detection of first- and
late-generation hybrids indicates; (3) patterns of natural introgression are correlated
with altitude; and (4) differences on the patterns were not detected between adults
and regeneration, suggesting early-acting reproductive isolating barriers. Knowledge
about natural occurrence of introgressive hybridization is relevant for seed collection, and it could be a possible source of contamination but also a source of genetic
variation for breeding programmes. For example, five hybrid individuals have been
detected using species-specific nuclear SSRs in a selected seed stand (SSS) of
N. alpina (251 individuals) installed in 1999 at Trevelin Forest Station of INTA and
registered with INASE (National Seed Institute) in 2017 (Pastorino et al. 2016; see
Chap. 3). Besides, the use of SSRs allowed determining that genetic diversity of the
SSS is similar to the average value of the natural distribution of the species in
Argentina. Moreover, genotype data of individuals from this SSS were also used to
construct a relationship matrix that is being used for the genetic evaluation of the
S. L. Torales et al.
among individuals. These results allowed the selection of trees, showing high stability at molecular and morphological level but conserving a percentage of variability,
based on high genetic distance individual criteria for selection. These trees will be
used in the Prosopis alba breeding.
In the case of Prosopis denudans, studies of genetic diversity and genetic structure of natural populations have been started in order to assist ecological restoration
and breeding programme (for biomass product) (Vivien Pentreath unpublished
data). It is a shrub (or small tree) of Patagonia adapted to the cold and semi-desert
steppe, thus showing tolerance to drought, salinity, alkalinity and cold. Neutral and
putative functional SSRs transferred from P. alba were used, revealing most of them
moderate to high degree of genetic diversity (e.g. average observed and expected
heterozygosities ranging from 0.324 to 0.732) and low genetic differentiation
between populations (F ST = 0.064). This work will be continued with more analyses
using molecular, morphometric and environmental data, in order to study the influence of the different factors on the genetic diversity of the species and to identify/
select better genotypes.
Among Nothofagus species, several studies have been carried out or started in
the last years based on the genomic resources and molecular markers developed by
high-throughput sequencing. Azpilicueta et al. (2016) using SSRs and Sanger
sequencing of nuclear Adh and ITS genome regions evaluated the taxonomic status
of Lagunas de Epulauquen population, the northernmost population of N. obliqua in
Argentina, which has been questioned due to its morphological, architectural and
genetic distinctiveness. The performed analysis revealed that individuals from this
population were closely related to other N. obliqua individuals, while the presumed
hybridization with N. alpina was not detected. This result supports the inclusion of
Lagunas de Epulauquen within Argentinean N. obliqua domestication and breeding
programmes, increasing the genetic diversity available for individual selection.
El Mujtar et al. (2017b) used six species-specific nuclear SSRs for the identification and classification of hybrids, in natural mixed forests of N. obliqua and
N. alpina, based on estimates of ancestry and interclass heterozygosity. Results
indicated that (1) introgressive hybridization occurs at a global rate of 7.8%; (2) F1
hybrids occur at a global rate of 3.8% and are fertile, as the detection of first- and
late-generation hybrids indicates; (3) patterns of natural introgression are correlated
with altitude; and (4) differences on the patterns were not detected between adults
and regeneration, suggesting early-acting reproductive isolating barriers. Knowledge
about natural occurrence of introgressive hybridization is relevant for seed collection, and it could be a possible source of contamination but also a source of genetic
variation for breeding programmes. For example, five hybrid individuals have been
detected using species-specific nuclear SSRs in a selected seed stand (SSS) of
N. alpina (251 individuals) installed in 1999 at Trevelin Forest Station of INTA and
registered with INASE (National Seed Institute) in 2017 (Pastorino et al. 2016; see
Chap. 3). Besides, the use of SSRs allowed determining that genetic diversity of the
SSS is similar to the average value of the natural distribution of the species in
Argentina. Moreover, genotype data of individuals from this SSS were also used to
construct a relationship matrix that is being used for the genetic evaluation of the
S. L. Torales et al.