Lipopeptides produced by Bacillus subtilis as new biocontrol products against fusariosis in ornamental plants

Abstract

In this study, we have investigated the effects of three lipopeptides (fengycin, surfactin and mycosubtilin) produced by different strains of Bacillus subtilis against the phytopathogenic fungi Fusarium oxysporum f. sp. iridacearum, which affects the ornamental bulb plant populations of Iris sp. The antifungal effects were tested using minimum inhibitory concentration assay, determination of mycelium growth and spore germination inhibition rates. Also, in vivo tests on infected rhizomes and scanning electron microscopy were employed. Mycosubtilin alone and in combination with fengycin or/and surfactin showed potent inhibitory activity at concentrations as low as 5 μg ml which is 100 times lower compared to Topsin M, a common chemical fungicide frequently used against fusariosis in ornamental plants. An enhancement of mycosubtilin antifungal activity was observed when it was used in combination with surfactin due to a synergistic effect. At a concentration of 20 μg ml, mycosubtilin inhibited the growth of the mycelium up to 49% and the spore germination ability up to 26% in comparison to control. In addition, significant changes on the macro- and micro-morphology have been observed. The antifungal activity is related to the inhibition of spore germination and the irreversible damage of the hyphae cell wall. To the best of our knowledge, this is the first attempt to propose the lipopeptides as biopesticides against the fusariosis of ornamental plants.

Crop Protection against Botrytis cinerea by Rhizhosphere Biological Control Agent Bacillus velezensis XT1

“…Previous studies have highlighted the crucial role played by surfactins and 2–3 butanediol as antimicrobial agents and as compounds which activate induced systemic resistance (ISR) and promote plant growth [ 32 , 78 , 79 , 80 , 81 ]. Strain XT1 produces these compounds [ 67 ] and other metabolites [ 61 ] which facilitate its antifungal and PGPR activities.…”

Antibacterial activity against Ralstonia solanacearum of the lipopeptides secreted from the Bacillus amyloliquefaciens strain FJAT ‐2349

“…Notably, iturin, surfactin and fengycin can also interact with each other in a synergistic manner to effectively enhance their bioactivities (Mihalache et al . ).…”

“…The antimicrobial activities of the LPs are determined by their molecular structure: iturin shows strong antifungal but limited antibacterial activity; fengycin is capable of inhibiting the growth of filamentous fungi; surfactin possesses broadspectrum antimicrobial, but weaker antifungal activity than iturin or fengycin. Notably, iturin, surfactin and fengycin can also interact with each other in a synergistic manner to effectively enhance their bioactivities (Mihalache et al 2018).…”

Bacillus Spp.: Efficient Biotic Strategy to Control Postharvest Diseases of Fruits and Vegetables

“…Researchers report the inhibitory function of Fusarium oxysporum fungus development by B. subtilis GM5 due to the presence of surfactin and fengycin at spore germination, sprouting tube formation, and hyphae branching phases [86]. Different studies associate an increase in antifungal activity with synergistic effects of fengycin and mycosubtilin [106]. The antibiotic capacity of LPs is associated with their ability to form micelles in the aqueous media and the membranotropic properties of these amphiphilic molecules, which disrupt the normal functioning of membranes due to their integration into the lipid bilayer and formation in pore membranes [103,107].…”