A conserved Delftibactin A biosynthetic gene cluster plays an important role in the biocontrol of kiwifruit bacterial canker by <i>Delftia lacustris</i> ZWP15

ABSTRACT Kiwifruit bacterial canker (KBC), caused by Pseudomonas syringae pv. actinidiae ( Psa ), is a globally devastating disease with limited sustainable control options. Here, we report Delftia lacustris strain ZWP15 as a novel biocontrol agent exhibiting strong antagonism against Psa in vitro and in field trials. Comparative genomics identified a conserved Delftibactin A biosynthetic gene cluster in ZWP15, which was functionally validated through gene knockout. Loss of the Delftibactin A biosynthetic gene cluster significantly impaired ZWP15’s antibacterial activity, while crude extracellular extracts from wild-type ZWP15 markedly inhibited Psa growth and suppressed key virulence traits, including motility, biofilm formation, and transcription of type III secretion system genes. Importantly, these extracts reduced Psa colonization and disease severity in kiwifruit plants, suggesting a dual role of Delftibactin A-associated metabolites in direct pathogen inhibition and virulence disruption. To our knowledge, this is the first demonstration of D. lacustris as a biocontrol agent against KBC. Our findings highlight the potential of exploiting the Delftibactin A biosynthetic gene cluster for developing sustainable alternatives to chemical bactericides. IMPORTANCE Kiwifruit bacterial canker (KBC) is a devastating disease with scarce sustainable management options. This study identifies Delftia lacustris as a novel and effective biocontrol agent against KBC. The key molecular mechanism underlying the antibacterial activity of Delftia lacustris ZWP15 is the production of Delftibactin A. Besides the direct antibacterial effect, Delftibactin A also uniquely disrupts key pathogenic pathways of the pathogen, including motility, biofilm formation, and the type III secretion system. This dual mode of action enhances its potential for sustained control of the disease. This study highlights the promising prospects of developing the Delftibactin A biosynthetic gene cluster into an environmentally friendly alternative to traditional copper-based bactericides.