Abstract
Phosphate-solubilizing fungi (PSF) generally enhance available phosphorus (P) released from soil, which contributes to plants’ P requirement, especially in P-limiting regions. In this study, two PSF, TalA-JX04 and AspN-JX16, were isolated from the rhizosphere soil of moso bamboo (Phyllostachys edulis) widely distributed in P-deficient areas in China and identified as Talaromyces aurantiacus and Aspergillus neoniger, respectively. The two PSF were cultured in potato dextrose liquid medium with six types of initial pH values ranging from 6.5 to 1.5 to assess acid resistance. Both PSF were incubated in Pikovskaya’s liquid media with different pH values containing five recalcitrant P sources, including Ca3(PO4)2, FePO4, CaHPO4, AlPO4, and C6H6Ca6O24P6, to estimate their P-solubilizing capacity. No significant differences were found in the biomass of both fungi grown in media with different initial pH, indicating that these fungi could grow well under acid stress. The P-solubilizing capacity of TalA-JX04 was highest in medium containing CaHPO4, followed by Ca3(PO4)2, FePO4, C6H6Ca6O24P6, and AlPO4 in six types of initial pH treatments, while the recalcitrant P-solubilizing capacity of AspN-JX16 varied with initial pH. Meanwhile, the P-solubilizing capacity of AspN-JX16 was much higher than TalA-JX04. The pH of fermentation broth was negatively correlated with P-solubilizing capacity (p<0.01), suggesting that the fungi promote the dissolution of P sources by secreting organic acids. Our results showed that TalA-JX04 and AspN-JX16 could survive in acidic environments and both fungi had a considerable ability to release soluble P by decomposing recalcitrant P-bearing compounds. The two fungi had potential for application as environment-friendly biofertilizers in subtropical bamboo ecosystem.
Highlights
According to the P fractionation method provided by Chang and Jackson (1957)[8], the inorganic P was divided into five main groups including soluble P, calcium phosphate, aluminum phosphate, iron phosphate and occluded P
The soluble P, which can be directly absorbed by plants, accounts for a little proportion in soil, while the rest of inorganic P, such as calcium phosphate, aluminum phosphate, iron phosphate exist with hard-to-dissolve forms [9]
18 isolates of the moso bamboo rhizosphere fungi were isolated from the three sampling sites, and TalA-JX04 and AspN-JX16 showed a clear zone of dissolved phosphate in solid Pikovskaya’s medium, which indicated that both these phosphate-solubilizing fungi (PSF) exhibited the desired P-solubilizing ability (Fig 1A and 1B)
Summary
Houz.) covers an area of 3.87 million ha, accounting for 70% of the bamboo forest area in China and 80% of its global distribution [1, 2]. It has become the main economic forest crop for satisfying the industrial requirement as well as improving forestry efficiency and farmers’ income [3, 4]. The soluble P, which can be directly absorbed by plants, accounts for a little proportion in soil, while the rest of inorganic P, such as calcium phosphate, aluminum phosphate, iron phosphate exist with hard-to-dissolve forms [9]. Besides the efficient use of P reserves, it is important to reduce the current wastage of P fertilizers and to recover applied P
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