Nematicidal Activity of Cyclopiazonic Acid Derived From Against Root-Knot Nematodes and Optimization of the Culture Fermentation Process.

Among 200 fungal strains isolated from the soil, only one culture filtrate of JCK-4087 showed strong nematicidal activity against . The nematicidal metabolite isolated from the culture filtrate of JCK-4087 was identified as cyclopiazonic acid (CPA). Because JCK-4087 also produced aflatoxins, six strains of , which have been reported to be CPA producers, were obtained from the bank and then tested for their CPA productivity. CPA was isolated from the culture filtrate of KACC 45973. CPA killed the second-stage juveniles of , and with EC 4.50, 18.82, and 60.51 μg mL, respectively. CPA also significantly inhibited egg hatch of and after a total of 28 days of treatment with the concentrations > 25 μg mL. The enhancement of CPA production by KACC 45973 was explored using an optimized medium based on Plackett-Burman design (PBD) and central composite design (CCD). The highest CPA production (381.48 μg mL) was obtained from the optimized medium, exhibiting an increase of 7.88 times when compared with that from potato dextrose broth culture. Application of the wettable power-type formulation of the ethyl acetate extract of the culture filtrate of KACC 45973 reduced gall formation and nematode populations in tomato roots and soils under greenhouse conditions. These results suggest that CPA produced by KACC 45973 can be used as either a biochemical nematicide or a lead molecule for developing chemical nematicides to control root-knot nematodes.