A piericidin-producing Streptomyces strain: identification and antagonistic activity on Xanthomonas oryzae

[Objective] The research and development and application of eco-friendly biopesticides for the sustainable agricultural development has received widespread concern. Microbial metabolite pesticide (MMP) is one of the most popular biopesticides in China and also one of the most important green pesticides to be developed. [Methods] The nutrient agar (NA) containing Xanthomonas oryzae pv. oryzae (Xoo) strain PXO99A was used to screen the anti-Xoo Streptomyces strain HSW2009. High performance liquid chromatography (HPLC) and mass chromatography (MS) were employed to characterize the chemical structure of the anti-Xoo metabolite produced by HSW2009. Xoo was inoculated into adult rice plants (Oryza sativa L. subsp. japonica) by leaf-clipping, followed by spraying with the piericidin solution (0.1 g/L). The length of spot was measured 2 weeks after inoculation. Response surface methodology was employed to optimize the fermentation medium. PacBio SMRT together with Illumina HiSeq X Ten was applied for genome sequencing. Average nucleotide identity (ANI) was compared to analyze the relationship between HSW2009 and other Streptomyces strains. [Results] A Streptomyces strain HSW2009 was detected to have strong inhibitory effect on Xoo growth and it produced the active metabolite piericidin A1 (PIE). PIE application mitigated Xoo infection on rice leaves. An optimized MFM medium was developed for PIE production. In MFM, HSW2009 grew well, with the highest fermentation titer of PIE reaching 0.72 g/L. HSW2009 was different from the known PIE-producing Streptomyces strains in colony phenotype, PIE biosynthetic gene cluster, whole genome sequence, and ANI. [Conclusion] HSW2009 is a representative of a candidate novel species of Streptomyces producing high level of PIE and is named as Streptomyces shaowuensis sp. nov. It has potential to be developed as an industrial strain for piericidin production.