283
and pod organoleptic characteristics (Felker et al. 2001). This study reported the
evaluation of a 9-year-old progeny trial containing 57 open-pollinated families of 8
provenances from Northwestern Argentina established in 1990 in the Province of
Santiago del Estero (27° 45′ S, 64° 15′ W, 200 m asl). The family-narrow-senseheritability was 0.487 for height, 0.548 for aerial biomass production, and 0.244 for
pod production. The mean values across families ranged from 10.7 kg/tree to
57.4 kg/tree for aerial biomass production, from 2.2 m to 3.6 m for height, and from
13 g/year to 874 g/year for pod production. Even though P. alba produces highly
nutritious fruits for forage and human food with commercial value (Fagg and
Stewart 1994), most studies have focused on traits related to wood production (Salto
2011; Cappa and Varona 2013; Carreras et al. 2016). Currently, ongoing studies
seek to estimate breeding values at tree level for flowering and fruiting traits (flowering intensity, production of pods, nutritional quality of fruits) using the INTA net
trials (Cisneros et al. in preparation).
The selection for wood yield requires improving traits like tree architecture,
trunk shape, and bole length. After the progeny trials of INTA net were established
in 2008, the families’ early growth and shape were evaluated at 18 months of age.
These studies reported significant interaction between provenance and environment
in diameter (ranged from 1 to 8 cm) and total height (ranged from 1 to 3 m) and a
negative correlation between tree form and the two growth traits (Salto 2011). This
represents a constraint for the breeding program, as trees selected for fast growth
would show low quality in terms of tree form. To overcome this limitation, Carreras
et al. (2016) evaluated genetic parameters for several traits of economic importance
in P. alba, including tree form (number of stems), height, diameter, and size increments using a multi-trait selection approach based on a selection index, with the
goal of getting the maximum possible gain in all traits simultaneously (Bessega
et al. 2015). They developed a breeding strategy for multiple trait selection taking
into account the heritability of individual traits, the genetic correlation between
them, and the increase of selected group kinship inherent to the selection process.
This issue is important for breeding to preserve wide genetic diversity and prevent
inbreeding depression in the following generations (Lindgren and Mullin 1997).
They reported that although gain at individual trait level is reduced in comparison
with the maximum potential, index selection allows significant gains for all three
traits together and represents a suitable strategy to improve P. alba in order to establish clonal seed orchards. This study evaluated only one progeny trial of INTA net,
and therefore no genotype x environment interaction was estimated. Currently,
height, diameter, and tree form at different ages, measured in the three trials, are
under analysis with individual tree mixed models (Borralho 1995) to predict breeding values and simultaneously estimate genetic and environmental effects (Cisneros
et al. in preparation). Current efforts in P. alba breeding program aim at expanding
the approaches to multiple uses (multipurpose selection) such as fruit production,
forage, recovery of degraded areas, biomass production, and environmental services, among others.
10 Genetic Breeding of Prosopis Species from the “Great American Chaco”
and pod organoleptic characteristics (Felker et al. 2001). This study reported the
evaluation of a 9-year-old progeny trial containing 57 open-pollinated families of 8
provenances from Northwestern Argentina established in 1990 in the Province of
Santiago del Estero (27° 45′ S, 64° 15′ W, 200 m asl). The family-narrow-senseheritability was 0.487 for height, 0.548 for aerial biomass production, and 0.244 for
pod production. The mean values across families ranged from 10.7 kg/tree to
57.4 kg/tree for aerial biomass production, from 2.2 m to 3.6 m for height, and from
13 g/year to 874 g/year for pod production. Even though P. alba produces highly
nutritious fruits for forage and human food with commercial value (Fagg and
Stewart 1994), most studies have focused on traits related to wood production (Salto
2011; Cappa and Varona 2013; Carreras et al. 2016). Currently, ongoing studies
seek to estimate breeding values at tree level for flowering and fruiting traits (flowering intensity, production of pods, nutritional quality of fruits) using the INTA net
trials (Cisneros et al. in preparation).
The selection for wood yield requires improving traits like tree architecture,
trunk shape, and bole length. After the progeny trials of INTA net were established
in 2008, the families’ early growth and shape were evaluated at 18 months of age.
These studies reported significant interaction between provenance and environment
in diameter (ranged from 1 to 8 cm) and total height (ranged from 1 to 3 m) and a
negative correlation between tree form and the two growth traits (Salto 2011). This
represents a constraint for the breeding program, as trees selected for fast growth
would show low quality in terms of tree form. To overcome this limitation, Carreras
et al. (2016) evaluated genetic parameters for several traits of economic importance
in P. alba, including tree form (number of stems), height, diameter, and size increments using a multi-trait selection approach based on a selection index, with the
goal of getting the maximum possible gain in all traits simultaneously (Bessega
et al. 2015). They developed a breeding strategy for multiple trait selection taking
into account the heritability of individual traits, the genetic correlation between
them, and the increase of selected group kinship inherent to the selection process.
This issue is important for breeding to preserve wide genetic diversity and prevent
inbreeding depression in the following generations (Lindgren and Mullin 1997).
They reported that although gain at individual trait level is reduced in comparison
with the maximum potential, index selection allows significant gains for all three
traits together and represents a suitable strategy to improve P. alba in order to establish clonal seed orchards. This study evaluated only one progeny trial of INTA net,
and therefore no genotype x environment interaction was estimated. Currently,
height, diameter, and tree form at different ages, measured in the three trials, are
under analysis with individual tree mixed models (Borralho 1995) to predict breeding values and simultaneously estimate genetic and environmental effects (Cisneros
et al. in preparation). Current efforts in P. alba breeding program aim at expanding
the approaches to multiple uses (multipurpose selection) such as fruit production,
forage, recovery of degraded areas, biomass production, and environmental services, among others.
10 Genetic Breeding of Prosopis Species from the “Great American Chaco”