Phyto-safe in vitro regeneration and harnessing antimicrobial-resistant endophytes as bioinoculants for enhanced growth and secondary metabolites yield in Nilgirianthus ciliatus

• Published in: BMC plant biology Vol. 24; no. 1; pp. 872 - 16
• Main Authors: Ram, Jeevan P S, Ramakrishnan, Rameshkumar, K, Pavan Kumar, Singh, Sudhir, R, Anitha Kumari, Govindan, Suresh, Selvaraj, Rathika, Manikandan, Ramesh
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 19.09.2024; BioMed Central; BMC
• Subjects: 16S rDNA gene sequencing; Acetic acid; Acid production; Anti-Infective Agents - pharmacology; Antibiotics; Bacteria; Benzyladenine; Biodiversity; Bioinoculants; Biomass; Botanical research; Cancer; Conservation; Defense mechanisms; Endophytes; Endophytes - physiology; Explants; Fungicides; Growth; Growth (Plants); Herbal medicine; In vivo methods and tests; Indoleacetic acid; Inoculation; Metabolites; Microorganisms; Micropropagation; Nilgirianthus ciliatus; Organic acids; Pesticides; Pharmacology; Phosphates; Physiological aspects; Phytosterols; Plant growth; Plant growth-promotion; Plant layout; Plant metabolites; PPM-tolerant endophytic bacteria; Preservatives; Propagation; Proteolysis; Regeneration; Regeneration (Biology); Regeneration - drug effects; rRNA 16S; Secondary Metabolism - drug effects; Secondary metabolites; Solubilization; Squalene; Sustainability; Sustainable agriculture; Thin layer chromatography; Wildlife conservation; India; PPM-tolerant endophytic bacteria; Bacillus cereus; 16S rDNA gene sequencing; Bioinoculants; Sustainable agriculture; Nilgirianthus ciliatus; Plant growth-promotion; Endophytes; Acinetobacter pittii
• DOI: 10.1186/s12870-024-05582-8
• ISSN: 1471-2229

Nilgirianthus ciliatus, extensively exploited for its pharmacological properties, is now classified as vulnerable. In vitro micropropagation offers a sustainable approach for ecological conservation and rational utilization of this biodiversity resource. This study aimed to reduce endophytes during in vitro propagation and isolating antimicrobial-resistant endophytes from N. ciliatus by employing various concentrations and exposure times of Plant Preservative Mixture (PPM). Optimal results were observed when nodal explants treated with 0.3% PPM for 8 h, followed by inoculation in Murashige and Skoog (MS) medium supplemented with 3 mg/L 6-benzylaminopurine (BAP) and 0.3% PPM. This protocol achieved 82% shoot regeneration with minimal endophytic contamination, suggesting that the duration of explant exposure to PPM significantly influences endophyte reduction. Two antimicrobial-resistant endophytes were isolated and identified as Bacillus cereus and Acinetobacter pittii through 16S rDNA sequencing. These endophytes exhibited plant growth-promoting characteristics, including amylolytic, proteolytic, lipolytic activities, indole-3-acetic acid production, phosphate solubilization, and stress tolerance. In vivo application of these endophytes as bioinoculants to N. ciliatus not only improved growth parameters but also significantly increased the levels of pharmacologically important compounds, squalene, and stigmasterol, as confirmed by High-performance thin-layer chromatography (HPTLC). This study demonstrates that PPM is a promising alternative for sustainable micropropagation of N. ciliatus. Furthermore, it highlights the potential of antimicrobial-resistant endophytes as bioinoculants to improve growth and medicinal value, offering a sustainable solution for conservation and large-scale cultivation of this species.