Agriculture Reference
In-Depth Information
phosphate (CaHPO
4
), calcium orthophosphate (Ca
3
(PO
4
)
2
), crystalline ferric phos-
phate (FePO
4
·4H
2
O), crystalline aluminium phosphate (AlPO
4
), colloidal ferric
phosphate or colloidal aluminium phosphate. Phosphate solubilization was highest
for CaHPO
4
(475 mg P/l), Ca
3
(PO
4
)
2
(360 mg P/l) and colloidal aluminium
phosphate (207 mg P/l). Phosphate solubilization was generally higher with ammo-
nium than the nitrate (Whitelaw et al.
1999
). Wakelin et al. (
2004
) also found
Penicillium
spp. exhibiting P-solubilizing activity both on and in the roots of wheat
plants grown in southern Australian agricultural soils. Of the different fungal
species,
P. bilaiae
strain RS7B-SD1 was the most effective, mobilizing 101.7 mg
P/l. Other effective strains included
P. simplicissimum
(58.8 mg P/l),
P. griseofulvum
(56.1-47.6 mg P/l) and
Talaromyces flavus
(48.6 mg P/l) and two
unidentified
Penicillium
spp. (50.7 and 50 mg P/l). A newly identified strain of
P. radicum
(KC1-SD1) could mobilize 43.3 mg P/l. Reyes et al. (
2007
) in a similar
study found six fungal strains belonging to the genus
Penicillium
endowed with
high hydroxyapatite dissolution capacities. Five of them had similar phenotypes to
P. rugulosum
IR94MF1 but they solubilized hydroxyapatite at different degrees
with both N sources. On the contrary, Vyas et al. (
2007
) showed high solubilization
of TCP, aluminium P, MRP and North Carolina RP by
E. parvum
. The organism
also exhibited tolerance against desiccation, salinity, acidity, aluminium and iron.
Similar reports on P solubilization by
P. restrictum
,
P. rugulosum
,
P. citrinum
,
P. islandicum
,
P. olivicolor
,
P. mellini
(Sharma et al.
2010
, Sharma
2011
),
P. citrinum
(Yadav et al.
2011a
,
b
) and
P. oxalicum
(Singh et al.
2011
) are available
in the literature. In a recent study, the TCP-solubilizing activity of two different
endophytic
Penicillium
species isolated from tea leaves was reported by Nath
et al. (
2012
). Both the isolates had remarkable PS activity up to 8 days with
consequent increase in the acidity of the medium. Tricalcium P-solubilizing activity
of species 1 ranged between 39.22
1.17 and 86.1
1.2
μ
g/ml, while that of
μ
species 2 varied between 32.57
1.41 and 84.25
1.5
g/ml following 2 to
10 days incubation (Figs.
4.1
and
4.2
).
4.5.3.2 Aspergillus
Barroso et al. (
2006
) studied the solubilization of CaHPO
4
and AlPO
4
by A. niger
using several C and N sources. Solubilization of Ca-P was enhanced when the C
sources were mannitol, maltose, galactose and glucose (in that order), while Al-P
was solubilized in the order: galactose
maltose. More extensive
growth, acid production and decrease in pH were recorded in the Al-P medium
than in the Ca-P medium. According to Gupta et al. (
2007
),
Aspergillus
isolated
from mangrove plants grown in Bhitarkanika, Orissa, showed good PS activity,
while Kang et al. (
2008
) found a “soil isolate”
Aspergillus
sp. which had excellent
potential to solubilize RP with occurrence of high levels of citric acid which also
caused a significant drop in pH of the medium. Similarly,
A. niger and A. fumigates
solubilized RP and TCP significantly (Hefnawy et al.
2009
). In other study, Singh
et al. (
2011
) showed that
A. niger
strain 1 could solubilize 285 mg P/ml, while
sucrose
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