Temperature-dependent production of cyclic lipopeptides by Pseudomonas fuscovaginae UPB0736 and its impact on Rhizoctonia solani suppression

Pseudomonas fuscovaginae, the causal agent of rice sheath brown rot, produces the cyclic lipopeptides (CLiPs) syringotoxin and fuscopeptin, with a dual role in phytotoxicity and antagonism against competing microorganisms. Up to now, produced CLiP quantities are too low for further biological studies. We aimed to optimize CLiP production and extraction to further investigate their antifungal effects. Bacteria were cultured at different temperatures in different liquid media. CLiPs were extracted using solid phase extraction and quantified and characterized by UPLC-MS/MS and NMR. Antifungal activity was assessed via IC 50 determinations in bioassays against Rhizoctonia solani . The highest CLiP production was reached at 18°C in liquid King’s B Medium in baffled flasks, reaching a 1000-fold increase for syringotoxin and a 5-fold increase for fuscopeptin, compared with incubation at 28°C in non-baffled flasks. Especially syringotoxin showed potent activity against Rhizoctonia , with IC 50 values of 0.02–0.09 mg/L. CLiP production in P. fuscovaginae is boosted at 18°C, promoting higher yields and stronger antifungal activity, especially for syringotoxin. These findings highlight the importance of environmental conditions in shaping antifungal efficacy and disease outcomes in rice-pathogen interactions. • CLiP production in Pseudomonas fuscovaginae is temperature-dependent. • Syringotoxin is identified as the key antifungal agent against Rhizoctonia solani. • Shaking conditions with increased aeration significantly increase CLiP yields.