Antifungal activity of Penicillium striatisporum Pst10 and its biocontrol effect on Phytophthora root rot of chilli pepper

Penicillium striatisporum Pst10 was isolated from the rhizosphere of chilli peppers. In dual culture agar plate assays, this isolate showed very high antagonistic effects on mycelium growth of Phytophthora spp., Cladosporium cucumerium, and Sclerotinia sclerotiorum. In in vitro assays, the toxicity of sterilized liquid culture filtrates (SLCF) of Pst10 grown in potato-dextrose broth (PDB) was tested against Phytophthora capsici mycelium growth and sporangia/spore formation or germination. The SLCF completely inhibited mycelium growth and even at a 100-fold dilution led to abnormal mycelium. A 20-fold dilution of SLCF inhibited formation and germination of sporangia and spores. Three antifungal substances were separated by thin-layer chromatography (TLC) from organic solvent extracts of liquid culture filtrate of Pst10. Composted pig manure slightly increased the colonization of the chilli rhizosphere by Pst10. In pot tests, the incidence of Phytophthora root rot of chilli was significantly reduced when artificially infested soil was treated with conidia and SLCF of Pst10.