Production And Application Of Syringomycin E As An Organic Fungicide Seed Protectant Against Pythium Damping-Off

Syringomycin E (SRE) is a cyclic lipodepsinonapeptide with potent antifungal activity and is produced by certain strains of Pseudomonas syringae pv.syringae. In this study, its potential as an organic-compatible agrofungicide and vegetable seed treatment against the soilborne pathogen Pythium ultimum var. ultimum was examined. A variant of P.syringae pv.syringae strain B301D with enhanced SRE-producing capabilities was isolated and grown in a bioreactor with SRE yields averaging 50mg/l in 40h. SRE was extracted and purified through a large-scale chromatography system using organic-compatible processes and reagents. The minimum concentrations of the purified product required to inhibit 50 and 90% of P.ultimum oospore germination were determined as 31.3 and 250g/ml, respectively. Drench treatment of cucumber seeds in P.ultimum-infested potting medium (500 oospores/g) with 50g/ml SRE or water with no SRE resulted in 90.2 +/- 4.5% and 65.7 +/- 4.6% germination rates, respectively. Seed coating with 0.03% (w/w) SRE allowed 65.7 +/- 4.6% seedlings to germinate on naturally infested soil while 100.0 +/- 0.0% of non-coated seeds were unable to germinate due to Pythium infection. Organic-compatible and scalably produced SRE is potentially a novel organic fungicide seed protectant.