259
applications, such as the development of programs for the conservation of diversity
and in genetic improvement assisted by molecular markers (Li et al. 2014; Song
et al. 2016). The genomic regions involved in the selection can be identified in natural populations by detecting outlier loci that exhibit non-neutral variation patterns
(Vitalis et al. 2001; Luikart et al. 2003). This is because local adaptation and directional selection reduce the genetic variation of these loci within populations and
increase the differentiation between populations (Stinchcombe and Hoekstra 2008).
By identifying these loci and excluding them from population analyses, better
approximations of the historical population parameters and of the genetic structuring product of the neutral processes can be obtained (Vitalis et al. 2001).
In particular, P. alba is the species of algarrobo of greater geographic distribution
of the genus in the Gran Chaco, and the one that has been most studied from the
genetic point of view. So far there are only studies on genetic variability using neutral molecular markers (Bessega et al. 2009; Bessega et al. 2011), which reflect
population dynamics and evolutionary forces such as genetic drift, mutation and
migration, but can only be related to processes of selection indirectly. The recent
sequencing of the transcriptome of P. alba and the analysis of candidate genes has
enabled the use of polymorphic markers of genome-coding regions related to
drought and salinity tolerance (Torales et al. 2013). These tools allow the direct
study of the adaptive genetic diversity of the species.
In Prosopis alba, it was recently studied the genetic structure of three natural
populations located in contrasting environmental conditions with respect to precipitation, using neutral molecular markers (Mottura et al. 2005; Bessega et al. 2013) as
well as potentially adaptive markers (EST-SSRs) (Torales et al. 2013). From the
analysis of F ST for detection of outlier loci, a strong signal of divergent selection was
detected in two markers, one EST-SSR (P73) and one genome microsatellite (gSSR)
(GL8). Both markers had high differentiation rates (GL8, F ST = 11.1 and P73,
F ST = 13.7%) (López Lauenstein 2019). The putatively neutral microsatellite marker
(GL8) was developed by Bessega et al. (2013) from the massive DNA sequencing
of three species of the Algarrobia section of the genus Prosopis (P. pallida, P. velutina, and P. glandulosa and putative hybrids). Since it comes from a massive
sequencing, it is possible that the marker is not in a noncoding region or, alternatively, that is strongly linked to a coding region. The P73 marker, on the other hand,
was developed from de novo sequencing of the P. alba transcriptome (Torales et al.
2013), so its location in a coding region is accurate, being its putative function associated to the pentatricopeptide repeat-containing protein (PPR) type. PPR proteins
are a large family of the “RNA binding protein” type, involved in gene expression
processes, mainly in organelles (Lurin et al. 2004), but also at the nuclear level. In
plants, progress has been made particularly with the characterization in the control
of processes where these proteins facilitate splicing, stability and transcription of
RNAs. Key roles have been cited for PPR proteins in response to various stresses
such as drought, salinity, and cold (Jiang et al. 2015) and also in general in response
to biotic and abiotic stresses (Xing et al. 2018).
Population genetic structure analysis reveals a strong structure among the three
natural populations studied (López Lauenstein 2019). However, when the two
9 Genetic Variation Patterns of “Algarrobos” from the “Great American Chaco…
applications, such as the development of programs for the conservation of diversity
and in genetic improvement assisted by molecular markers (Li et al. 2014; Song
et al. 2016). The genomic regions involved in the selection can be identified in natural populations by detecting outlier loci that exhibit non-neutral variation patterns
(Vitalis et al. 2001; Luikart et al. 2003). This is because local adaptation and directional selection reduce the genetic variation of these loci within populations and
increase the differentiation between populations (Stinchcombe and Hoekstra 2008).
By identifying these loci and excluding them from population analyses, better
approximations of the historical population parameters and of the genetic structuring product of the neutral processes can be obtained (Vitalis et al. 2001).
In particular, P. alba is the species of algarrobo of greater geographic distribution
of the genus in the Gran Chaco, and the one that has been most studied from the
genetic point of view. So far there are only studies on genetic variability using neutral molecular markers (Bessega et al. 2009; Bessega et al. 2011), which reflect
population dynamics and evolutionary forces such as genetic drift, mutation and
migration, but can only be related to processes of selection indirectly. The recent
sequencing of the transcriptome of P. alba and the analysis of candidate genes has
enabled the use of polymorphic markers of genome-coding regions related to
drought and salinity tolerance (Torales et al. 2013). These tools allow the direct
study of the adaptive genetic diversity of the species.
In Prosopis alba, it was recently studied the genetic structure of three natural
populations located in contrasting environmental conditions with respect to precipitation, using neutral molecular markers (Mottura et al. 2005; Bessega et al. 2013) as
well as potentially adaptive markers (EST-SSRs) (Torales et al. 2013). From the
analysis of F ST for detection of outlier loci, a strong signal of divergent selection was
detected in two markers, one EST-SSR (P73) and one genome microsatellite (gSSR)
(GL8). Both markers had high differentiation rates (GL8, F ST = 11.1 and P73,
F ST = 13.7%) (López Lauenstein 2019). The putatively neutral microsatellite marker
(GL8) was developed by Bessega et al. (2013) from the massive DNA sequencing
of three species of the Algarrobia section of the genus Prosopis (P. pallida, P. velutina, and P. glandulosa and putative hybrids). Since it comes from a massive
sequencing, it is possible that the marker is not in a noncoding region or, alternatively, that is strongly linked to a coding region. The P73 marker, on the other hand,
was developed from de novo sequencing of the P. alba transcriptome (Torales et al.
2013), so its location in a coding region is accurate, being its putative function associated to the pentatricopeptide repeat-containing protein (PPR) type. PPR proteins
are a large family of the “RNA binding protein” type, involved in gene expression
processes, mainly in organelles (Lurin et al. 2004), but also at the nuclear level. In
plants, progress has been made particularly with the characterization in the control
of processes where these proteins facilitate splicing, stability and transcription of
RNAs. Key roles have been cited for PPR proteins in response to various stresses
such as drought, salinity, and cold (Jiang et al. 2015) and also in general in response
to biotic and abiotic stresses (Xing et al. 2018).
Population genetic structure analysis reveals a strong structure among the three
natural populations studied (López Lauenstein 2019). However, when the two
9 Genetic Variation Patterns of “Algarrobos” from the “Great American Chaco…