Molecular Characterization and Heavy Metal Tolerant Potential of Plant Growth-Promoting Fungi Isolated from Rhizospheric Soil
G. Umanu *
Microbiology Unit, Department of Biological Sciences, Bells University of Technology Ota, Ogun State, Nigeria.
C. C. Obi
Biotechnology Unit, Department of Biological Sciences, Bells University of Technology Ota, Ogun State, Nigeria.
J. A. Odunlami
Microbiology Unit, Department of Biological Sciences, Bells University of Technology Ota, Ogun State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Aim: The overall aim was to isolate plant growth-promoting fungi from rhizospheric soil, assess their heavy metal tolerant potential and identify them molecularly.
Study Design: The study adopted a Completely Randomized Design (CRD) carried out with ten rhizospheric soil samples.
Place and Duration of Study: This study was conducted in the Microbiology Laboratory 2, Department of Biological Sciences, Bells University of Technology, Ota, Ogun State, Nigeria, between 2023 and 2024.
Methodology: Rhizospheric soil samples were collected around ten randomly selected maize plant roots. Fungi were isolated by spread plate technique and the isolated fungi were investigated for plant growth promoting traits by assaying for phosphate solubilization and indole acetic acid (IAA) production. Their heavy metal tolerant potential was assessed by growing them on potato dextrose broth supplemented with different concentrations (6, 12 and 18 mM) of zinc sulphate and lead (II) chloride. Fungal isolates were identified based on colonial characteristics and sequencing of the genes within their internally transcribed spacer (ITS).
Results: Out of twenty (20) fungi isolated, seven (7) isolates (35%) solubilized inorganic phosphate with solubilisation index (SI) ranging from 1.08 to 2.40. All the fungal isolates produced indole acetic acid (0.34 to 2.02 mg/ml). The best five fungi with characteristics that promote plant growth were identified as Aspergillus brunneoviolaceus strain OU1 (OR342229), Penicillium oxalicum strain OU2 (OR342230), Aspergillus brunneoviolaceus strain OU3 (OR342231), Aspergillus welwitschiae strain OU4 (OR342232) and Penicillium oxalicum strain OU5 (OR342233). These fungi grew well in medium that contain zinc sulphate and lead (II) chloride.
Conclusion: Rhizospheric fungi isolated in this study have the potential to improve plant growth and tolerate varying concentrations of heavy metals. Therefore, they could be used as potential candidates for biofertilizers in sustainable agriculture.
Keywords: Plant growth-promotion, fungi, soil, indole acetic acid, phosphate solubilization, heavy metal