Plant Growth-promoting Potentials of Mycoendophytes Associated with Medicinal Herb Argemone mexicana L.

Abstract

Aims: Argemone mexicana L., a ubiquitous, medicinally important herb that possesses therapeutic properties used in traditional medicine. It hosts a diverse species of mycoendophytes. Their use in promoting plant development has not yet been investigated. Hence, this study aimed to investigate the potentials of the mycoendophytes of A. mexicana as plant growth promoters. Study Design:  The experimental design included the analysis of plant growth-promoting properties of selected mycoendophytes from the plant Argemone mexicana through different qualitative and quantitative assays. Place and Duration of Study: Department of Microbiology, Davangere University, Davangere, Karnataka, from November 2023 to January 2025. Methodology: Different mycoendophytes isolated from healthy tissues of Argemone mexicana, the Aspergillus luchuensis (DUMB 210 and DUMB 222), Penicillium dierckxii (DUMB 208), and Penicillium restrictum (DUMB 211) were selected based on their antimicrobial properties. They were examined for their abilities to solubilize the nutrients through plate assays and Solubilization Index (SI) was calculated as ratio between diameter of zone of clearance and colony diameter. The Indole-3-acetic acid (IAA) and siderophore production were detected using Salkowski’s reagent method and on Chrome Azurol S (CAS) agar medium respectively. Ammonia secretion was analysed using the Nessler’s reagent, and the nitrogen fixation was determined in nitrogen-free media. The effects of fungal seed treatment on seed germination and seedling vigour of sorghum and green gram were evaluated by rolled paper-towel method. Results: Phosphate, potassium, and zinc solubilization potentials were exhibited by all the four mycoendophytes. The isolates of Aspergillus luchuensis (DUMB 210 and DUMB 222) displayed greater potassium and zinc solubilization with SI of 1.36±0.02 and 1.61±0.01 for potassium, and SI of 2.58±0.11 and 2.39±0.03 for zinc respectively. Further, they were also highly potential producers of IAA with 139.47±3.40 µg/ml and 112.22±3.86 µg/ml of culture filtrate. The Penicillium spp. were not producing siderophores. All the isolates showed maximum ammonia production and also capable of nitrogen fixation. The fungal culture filtrate and the fungal biomass of P. restrictum (DUMB 211) significantly improved both sorghum and green gram seedling vigour and biomass. Thereby, the P. restrictum (DUMB 211) was the potential fungal isolate to promote early seedlings growth. Conclusion: The potential of mycoendophytes from A. mexicana was established in plant growth promotion. These fungi may be used for seed biopriming in sustainable agriculture.