Polyyne-producing suppress damping-off disease of (pea).

Extensive crop losses are caused by oomycete and fungal damping-off diseases. Agriculture relies heavily on chemical pesticides to control disease, but due to safety concerns multiple agents have been withdrawn. were successfully used as commercial biopesticides because of their fungicidal activity and plant protective traits. However, their potential for opportunistic pathogenicity led to a moratorium on their registration as biopesticides. Subsequently, were shown to produce multiple specialised metabolites including potent antimicrobial polyynes. Cepacin A, a polyyne produced by biopesticide strains was shown to be an important metabolite for the protection of germinating peas against (formerly ) damping-off disease. Recently, there has been an expansion in bacterial polyyne discovery, with the metabolites and their biosynthetic gene pathways found in several bacterial genera including , , , and . To define the efficacy of these bacterial polyyne producers as biopesticidal agents, we systematically evaluated metabolite production, microbial antagonism, and biocontrol across a panel of 30 strains representing four bacterial genera. polyyne production and antimicrobial activity was demonstrated for most strains, but only polyyne producers were protective within the damping-off pea protection model. was the most effective cepacin-expressing biopesticide, and despite their known potential for plant pathogenicity and were uniquely shown to be protective as caryoynencin-producing biopesticides. In summary, are effective biopesticides due to their suite of antimicrobials, but the ability to deploy polyyne metabolites, caryoynencin and cepacin, is strain and species dependent. Graphical Abstract.