In vitro evaluation of the bioherbicide effects of soluble metabolites derived from microbial phytopathogens on two weeds

Abstract

The restriction on glyphosate-based herbicides has intensified the need for innovative and eco-friendly alternatives for weed management. In this context, phytopathogenic microorganisms represent a promising and sustainable source of bioactive compounds for herbicidal applications. This study explored the potential of soluble metabolites derived from selected phytopathogens to inhibit the growth of broad- and narrow-leaf weed species. Fungal strains including Fusarium oxysporum f. sp. cubense Race 1 (FocR1, CNRF-MIC17192), Fusarium spp. (LsF9, LsF11), Sclerotinia sclerotiorum (Ss4), Sclerotium cepivorum (Sc1), Colletotrichum sp., Rhizoctonia solani, and the bacterial strain Pectobacterium carotovorum were cultured in liquid media for 7 days. The resulting metabolites were filtered and applied to the foliage of two model plants: Amaranthus hybridus (broad-leaf) and Festuca arundinacea (narrow-leaf). Their phytotoxic effects were compared to a commercial glyphosate-based herbicide (Faena Fuerte® 360) over a 15-day period. Among the tested strains, CNRF-MIC17192 and Ss4 showed the highest efficacy on the broad-leaf plant, reducing chlorophyll content by approximately 65 % and biomass by 74 %. Conversely, metabolites from P. carotovorum exhibited the strongest effects on the narrow-leaf species, decreasing chlorophyll by 80 % and biomass by 70 %. Although the phytotoxicity of microbial metabolites was generally lower than that of chemical herbicide, the results underscore their potential as environmentally friendly bioherbicides for sustainable weed control. Preliminary results indicate that secondary metabolites contain enzymes with activity, such as cellulase and xylanase. In this context, P. carotovorum and Ss4 produced between ∼3.3 and ∼1.9 more activity than CNRF-MIC17192 strain.