The biocontrol roles of cyclic lipopeptide putisolvin produced from Pseudomonas capeferrum HN2-3 on the Phytophthora blight disease in cucumbers

In this study, a strain HN2-3 was isolated from a rhizosphere soil sample of Setaria viridis plants. The genome size of the strain HN2-3 was 5,966,659 bp, with a GC content of 62.47%. In addition, the strain HN2-3 contains a 31,784 bp plasmid pHN2-3. The strain HN2-3 was characterized as Pseudomonas capeferrum by the combination of 16S rRNA gene-based phylogenetic analysis and Type (Strain) Genome Server (TYGS). Moreover, the cyclic lipopeptide (CLP) produced from P. capeferrum HN2-3 was isolated and purified from the bacterial supernatant by acid-aided precipitation and high-performance liquid chromatography (HPLC). A purified CLP (1) was characterized as putisolvin by genome mining, bioinformatic analyses, high-resolution mass spectrometry (HR-MS) and high-resolution tandem mass spectrometry (HR-MS/MS). Further in vitro assays showed that 10 and 50 μM putisolvin-treated zoospore suspension of Phytophthora capsici displayed the significant difference on lysis ability of zoospores compared to 1 μM putisolvin-treated zoospores. In addition, planta assay has revealed that only 50 μM putisolvin-treated zoospore suspension of Phytophthora capsici displayed a significant decreasing on Phytophthora blight disease in cucumbers. Overall, this study has indicated that putisolvin produced from P. capeferrum HN2-3 could be developped as a biopesticide for the management of Phytophthora blight disease in cucumbers.