Exploring the Potential Herbicidal Activity of Actinomycetes Isolated from Western Ghats Soil, India

Eco-friendly alternatives to synthetic herbicides have yet to be fully explored. Global research into the herbicidal activity of microorganisms remains crucial. The Western Ghats of India, a hub for rich biodiversity, are home to various microorganisms whose potential as herbicidal agents has yet to be investigated. Therefore, this study aimed to isolate actinomycetes from the Western Ghats as a natural source of bioherbicides. A total of 20 isolates were isolated. Ten actinomycete isolates were selected based on pigment production and standardized to 5 × 10⁷ cells/mL for assessment of herbicidal activity. The isolates were identified through 16S rRNA gene amplification and sequencing. Pre-emergence assays revealed, among the isolates, Isolate '20' exhibiting the highest herbicidal activity (22 ± 0.78%), followed by Isolate '15' (20 ± 0.72%) and '10' (19.6 ± 0.82%). Post-emergence treatments leading to significant wilting and necrosis in pigweed within 7 days, further demonstrating their bioherbicidal potential. Electrolytic leakage assays revealed higher membrane disruption by isolates 4 and 20 (up to 1.5 and 1.2 µS/cm, respectively), while isolates 3, 9, 10, and 17 showed lower leakage values (0.8-1.3 µS/cm). Chlorophyll analysis indicated significant reductions by isolates 10, 11, 12, 19, 15, 17, and 3, with levels ranging from 0.094 ± 0.0006 µg/mL to 0.157 ± 0.0006 µg/mL. Notably, isolate 17 showed the greatest reduction (0.094 ± 0.0006 µg/mL), followed by isolate 3 (0.106 ± 0.0006 µg/mL). PCR amplification of the nlp gene confirmed the presence of non-ribosomal peptide biosynthesis linked to phytotoxicity. Optimal culture conditions were also established to enhance herbicidal activity.

The online version contains supplementary material available at 10.1007/s12088-025-01539-z.