285
individuals from the natural population and also adapt field materials to controlled
conditions, looking to obtain uninodal segments to establish in vitro cultures.
Rooting of cuttings of rejuvenated material was also tested. Salto et al. (2012)
selected 50 individuals of P. alba from the evaluation of a progeny trial installed in
Laguna Yema. A multi-criteria selection index was calculated, considering the
growth (diameter at the base and height) and the shape of the stem. The selection
was made with the estimation of the individual improvement values at the third year
of planting (Salto 2011). The 50 selected genotypes were coppiced in late winter
(August) at a height of 20–25 cm, using a chainsaw. The stumps were sealed with a
pruning bandage. The shoot harvesting campaigns took place at three moments in
time (41, 61, and 110 days after coppicing). The length and diameter of shoots
ranged from 15 to 70 cm and 2 to 6 mm, respectively. At the greenhouse, plant cuttings of 8–10 cm long were conditioned leaving two leaves reduced to a 50% in
area. Then, the cutting bases were treated with indole-3-butyric acid at a 0.45 g/kg
concentration as root inducer, using microbiological talc as vehicle. The rooting
percentage of the plant cuttings brought from the field showed values ranging from
12.5% to 100% among genotypes (López Lauenstein et al. 2016).
Likewise, grafting adult plants on juvenile rootstocks provides rejuvenated material with the goal of establishing a propagation system for macro-cuttings. In P. alba
and, as mentioned, in other species (Wendling et al. 2014), rejuvenated material is
the most efficient way to achieve rooting of cuttings (de Souza and Felker 1986;
Arce and Balboa 1991; Oberschelp and Marcó 2010). In recent years, de Souza
et al. (2014) have implemented the mini-cuttings technique, which consists on the
use of buds of mother plants under controlled conditions in order to generate a
degree of rejuvenation and a lower lignification. These authors indicate that the
mini-cutting have good rhizogenic capacity with rooting percentages ranged from
98% to 100%.
10.5 Beneficial Microorganisms
Soil microbiomes play important roles in terrestrial ecosystem regulation and functioning, impacting on productivity, diversity, and structure of plant communities.
Different types of abiotic stress like drought, salinity, high temperatures, and low
nutrient availability acting either alone or in combination have a strong influence on
plant diversity, conditioning their survival. Usually plants coevolve with the biodiversity of soil microorganisms and mutual relationships between them exist. The
use of rhizobia and mycorrhizal inoculants in nurseries is a strategy to improve the
adaptation and survival of seedlings in transplanting to the field, both in wood production plantations and in restoration or ecosystem recovery plans. Therefore, isolation and characterization of specific strains of these microorganisms is highly valued
in order to incorporate them into a technological package with the genetic breeding
of plant germplasm.
10 Genetic Breeding of Prosopis Species from the “Great American Chaco”
individuals from the natural population and also adapt field materials to controlled
conditions, looking to obtain uninodal segments to establish in vitro cultures.
Rooting of cuttings of rejuvenated material was also tested. Salto et al. (2012)
selected 50 individuals of P. alba from the evaluation of a progeny trial installed in
Laguna Yema. A multi-criteria selection index was calculated, considering the
growth (diameter at the base and height) and the shape of the stem. The selection
was made with the estimation of the individual improvement values at the third year
of planting (Salto 2011). The 50 selected genotypes were coppiced in late winter
(August) at a height of 20–25 cm, using a chainsaw. The stumps were sealed with a
pruning bandage. The shoot harvesting campaigns took place at three moments in
time (41, 61, and 110 days after coppicing). The length and diameter of shoots
ranged from 15 to 70 cm and 2 to 6 mm, respectively. At the greenhouse, plant cuttings of 8–10 cm long were conditioned leaving two leaves reduced to a 50% in
area. Then, the cutting bases were treated with indole-3-butyric acid at a 0.45 g/kg
concentration as root inducer, using microbiological talc as vehicle. The rooting
percentage of the plant cuttings brought from the field showed values ranging from
12.5% to 100% among genotypes (López Lauenstein et al. 2016).
Likewise, grafting adult plants on juvenile rootstocks provides rejuvenated material with the goal of establishing a propagation system for macro-cuttings. In P. alba
and, as mentioned, in other species (Wendling et al. 2014), rejuvenated material is
the most efficient way to achieve rooting of cuttings (de Souza and Felker 1986;
Arce and Balboa 1991; Oberschelp and Marcó 2010). In recent years, de Souza
et al. (2014) have implemented the mini-cuttings technique, which consists on the
use of buds of mother plants under controlled conditions in order to generate a
degree of rejuvenation and a lower lignification. These authors indicate that the
mini-cutting have good rhizogenic capacity with rooting percentages ranged from
98% to 100%.
10.5 Beneficial Microorganisms
Soil microbiomes play important roles in terrestrial ecosystem regulation and functioning, impacting on productivity, diversity, and structure of plant communities.
Different types of abiotic stress like drought, salinity, high temperatures, and low
nutrient availability acting either alone or in combination have a strong influence on
plant diversity, conditioning their survival. Usually plants coevolve with the biodiversity of soil microorganisms and mutual relationships between them exist. The
use of rhizobia and mycorrhizal inoculants in nurseries is a strategy to improve the
adaptation and survival of seedlings in transplanting to the field, both in wood production plantations and in restoration or ecosystem recovery plans. Therefore, isolation and characterization of specific strains of these microorganisms is highly valued
in order to incorporate them into a technological package with the genetic breeding
of plant germplasm.
10 Genetic Breeding of Prosopis Species from the “Great American Chaco”