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This research examines how Streptomyces griseoviridis culture filtrate affects the germination and growth of legumes.

June 26, 2026Open Access

Seed priming with Streptomyces griseoviridis culture filtrate: species-specific enhancement of legume germination and seedling vigor through hormonal and metabolic signaling

Key Points

This research examines how Streptomyces griseoviridis culture filtrate affects the germination and growth of legumes.
Isolated a strain of S. griseoviridis and characterized it molecularly.
Analyzed culture filtrate using HPLC and GC-MS.
Primed seeds of Phaseolus vulgaris and Vicia faba with varying concentrations of culture filtrate.
In P. vulgaris, 25% culture filtrate improved germination percentage to 66.7%, and stem length to 20.80 cm versus control.
For V. faba, 10% culture filtrate achieved 100% germination percentage and increased total pigments to 3.11 mg/g.
Soluble protein content in P. vulgaris reached 165.4 mg/g with 25% CFF, and in V. faba, 295.4 mg/g with 10% CFF.

Abstract

BACKGROUND: Actinobacteria of the genus Streptomyces are recognized as prolific producers of bioactive metabolites capable of regulating plant growth and stress responses. However, isolate-level phytohormone data for Streptomyces griseoviridis, a commercially relevant biocontrol species, remain limited and sometimes contradictory. RESULTS: A strain of S. griseoviridis was isolated and molecularly characterized. High-performance liquid chromatography (HPLC) of its cell-free culture filtrate (CFF) revealed the presence of gibberellic acid (46.68 µg/100 mL), zeatin (18.90 µg/100 mL), indole-3-acetic acid (3.93 µg/100 mL), and abscisic acid (0.38 µg/100 mL), while gas chromatography-mass spectrometry (GC-MS) identified oleic acid (17.1%) and palmitic acid methyl ester (8.34%) as major metabolites. Seeds of Phaseolus vulgaris and Vicia faba were primed with varying concentrations of CFF. In P. vulgaris, the 25% CFF significantly enhanced germination percentage (GP; 66.7% vs. 60.0% control), germination energy (GE; 56.7 vs. 41.7), germination rate index (GRI; 4.02 vs. 3.11), stem length (20.80 vs. 16.10 cm), and total photosynthetic pigments (3.79 vs. 2.8 mg/g). In V. faba, the 10% CFF proved most effective, achieving 100% GP (control: 98.3%), increasing GE and GRI, reducing mean germination time, and elevating total pigments (3.11 vs. 1.86 mg/g). Regarding soluble metabolites, soluble protein content in P. vulgaris was maximized by the 25% and 50% CFF treatments, reaching 165.4 and 136.8 mg/g dry weight, respectively, compared to 108.9 mg/g in the control, while soluble sugars increased with 10% CFF concentrations. In V. faba, the highest soluble protein concentration (295.4 mg/g) was achieved at 10% CFF (control: 202.1 mg/g), whereas soluble sugars reached a maximum at 100% CFF. Molecular docking revealed compound 2-acetyl-3-(2-cinnamido)ethyl-7-methoxyindole (indole-related) exhibited strong binding to NCED1 (- 7.85 kcal/mol), CCD1 (- 9.21 kcal/mol), starch phosphorylase (- 7.03 kcal/mol), and AGPase (- 6.56 kcal/mol), outperforming controls and fatty acid derivatives. CONCLUSION: The culture filtrate of Streptomyces griseoviridis constituted a biologically active signaling pool capable of modulating legume primary metabolism and photosynthetic pigment profiles in a species- and concentration-dependent manner. This study provided novel isolate-level evidence of the hormonal and metabolic effects of S. griseoviridis filtrates and pointed out the potential of plant growth-promoting Streptomyces species as sustainable drivers of crop productivity and food security.

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