9 Phosphate Solubilization by Endophytes from the Tropical Plants
219
health. Because of the health effects of pollution related to chemical fertilizers and
pesticides, interest in finding alternative green methods (Abo Nouh 2019). The use
of microbial plant growth promoters is an alternative to conventional agricultural
technologies. In this context, endophytes play an important role in growth promotion
and resistance to various biotic and abiotic stresses and diseases in plants (Abo Nouh
2019; Azevedo and Quecine 2019). Similar to PGPR, these microorganisms have
great potential to be used as safe and cost-effective alternatives to chemical fertilizers
due to their wide range of plant growth-promoting activities (Abo Nouh 2019).
The reduced availability of P in potentially productive acidic soils such as the
Brazilian savanna requires plants to associate symbiotically with microorganisms,
such as endophytes, that are adapted to those soil conditions (Zapata and Axmann
1995) and alter complexes that adsorb phosphate under acidic conditions, including
FePO 4 and AlPO 4 (Andrade et al. 2003). The plant growth-promoting effects of endophytes include increased plant height and biomass of shoots, stems, and roots; lignification of the xylem vessels; and increased crop yield (Azevedo and Quecine 2019).
In this context, phosphorus deficiency limits agricultural production, especially in
acidic soils such as those of the Brazilian savanna (Nakayama et al. 1998). In this
biome, the water-soluble P is transformed into iron phosphate (FePO 4 ) and aluminum
phosphate (AlPO 4 ) (Silva et al. 2011), which are moderately soluble complexes (Son
et al. 2006; Yadav et al. 2010; Chai et al. 2011).
On the other hand, Vitorino et al. (2012) reported the capacity of endophytic fungi
isolated from roots of Hyptis marrubioides Epling, a Brazilian savanna species, to
solubilize calcium phosphate in GELP medium and iron phosphate in modified Reyes
basal medium. Of six fungal strains analyzed by solubilization assays, none of the
fungi tested solubilized CaHPO 4 . In contrast, all of these fungi demonstrated the
capacity to solubilize high levels of FePO 4 . These authors suggested that none of the
fungi strains tested solubilized CaHPO 4 may be related to the fact that these fungi
were isolated from the root system of H. marrubioides Epling, a plant adapted to
acidic soil, in which P is bound to Fe
3+ and to Al
3+ (Khan et al. 2009). According
to Sharma and Roy (2015), fungal endophytes were isolated from root, stem, and
leaves of the plant Amaranthus spinosus, a species occurring in the savanna biome,
stated that endophytic fungal isolates of the plant A. spiunosus showed a positive test
for phosphate solubilization. The phosphate solubilization efficiency was found to
be highest for the fungal genera Aspergillus isolated from the stem of the plant.
In our research group, Torres (2018) studied 66 endophytic fungi isolated from
Stryphnodendron adstringens and Solanum lycocarpum St. Hill collected in the
Brazilian Tropical Savanna Reserve of the Federal University of São Carlos, Brazil.
Healthy leaves and stems of both plants were collected and submitted to superficial
asepsis. After incubation of the botanical material, isolation and molecular identification of the endophytic fungi were performed. The endophytic strains were evaluated
in vitro for the solubilization of inorganic phosphate. These strains showed promise
because of their ability to solubilize inorganic phosphate with mean phosphate solubilization indexes ranging from 1.46 to 1.93 and 1.19 to 2.61 for the strains isolated
from S. adstringens and S. lycocarpum, respectively.
219
health. Because of the health effects of pollution related to chemical fertilizers and
pesticides, interest in finding alternative green methods (Abo Nouh 2019). The use
of microbial plant growth promoters is an alternative to conventional agricultural
technologies. In this context, endophytes play an important role in growth promotion
and resistance to various biotic and abiotic stresses and diseases in plants (Abo Nouh
2019; Azevedo and Quecine 2019). Similar to PGPR, these microorganisms have
great potential to be used as safe and cost-effective alternatives to chemical fertilizers
due to their wide range of plant growth-promoting activities (Abo Nouh 2019).
The reduced availability of P in potentially productive acidic soils such as the
Brazilian savanna requires plants to associate symbiotically with microorganisms,
such as endophytes, that are adapted to those soil conditions (Zapata and Axmann
1995) and alter complexes that adsorb phosphate under acidic conditions, including
FePO 4 and AlPO 4 (Andrade et al. 2003). The plant growth-promoting effects of endophytes include increased plant height and biomass of shoots, stems, and roots; lignification of the xylem vessels; and increased crop yield (Azevedo and Quecine 2019).
In this context, phosphorus deficiency limits agricultural production, especially in
acidic soils such as those of the Brazilian savanna (Nakayama et al. 1998). In this
biome, the water-soluble P is transformed into iron phosphate (FePO 4 ) and aluminum
phosphate (AlPO 4 ) (Silva et al. 2011), which are moderately soluble complexes (Son
et al. 2006; Yadav et al. 2010; Chai et al. 2011).
On the other hand, Vitorino et al. (2012) reported the capacity of endophytic fungi
isolated from roots of Hyptis marrubioides Epling, a Brazilian savanna species, to
solubilize calcium phosphate in GELP medium and iron phosphate in modified Reyes
basal medium. Of six fungal strains analyzed by solubilization assays, none of the
fungi tested solubilized CaHPO 4 . In contrast, all of these fungi demonstrated the
capacity to solubilize high levels of FePO 4 . These authors suggested that none of the
fungi strains tested solubilized CaHPO 4 may be related to the fact that these fungi
were isolated from the root system of H. marrubioides Epling, a plant adapted to
acidic soil, in which P is bound to Fe
3+ and to Al
3+ (Khan et al. 2009). According
to Sharma and Roy (2015), fungal endophytes were isolated from root, stem, and
leaves of the plant Amaranthus spinosus, a species occurring in the savanna biome,
stated that endophytic fungal isolates of the plant A. spiunosus showed a positive test
for phosphate solubilization. The phosphate solubilization efficiency was found to
be highest for the fungal genera Aspergillus isolated from the stem of the plant.
In our research group, Torres (2018) studied 66 endophytic fungi isolated from
Stryphnodendron adstringens and Solanum lycocarpum St. Hill collected in the
Brazilian Tropical Savanna Reserve of the Federal University of São Carlos, Brazil.
Healthy leaves and stems of both plants were collected and submitted to superficial
asepsis. After incubation of the botanical material, isolation and molecular identification of the endophytic fungi were performed. The endophytic strains were evaluated
in vitro for the solubilization of inorganic phosphate. These strains showed promise
because of their ability to solubilize inorganic phosphate with mean phosphate solubilization indexes ranging from 1.46 to 1.93 and 1.19 to 2.61 for the strains isolated
from S. adstringens and S. lycocarpum, respectively.