Activity of antimicrobial peptides on Xanthomonas arboricola pv. pruni populations and infection on Prunus sp.

Abstract: Xanthomonas arboricola pv. pruni is the causal agent of bacterial spot disease of
stone fruits (Prunus spp.), an economically important disease in the major stone-fruit-producing areas worldwide. Disease control is mainly achieved by preventive applications of copperbased plant protection products. However, due to the negative environmental impact, there is a strong demand to reduce copper use in crop protection. Antimicrobial peptides are an alternative to conventional compounds used in plant disease control. This work was aimed at evaluating the activity of antimicrobial peptides against X. arboricola pv. pruni in vitro and on host plants. Antimicrobial peptide BP100 and two of its derivatives were able to inhibit bacterial growth in vitro, with minimal inhibitory concentration from 2.5 to 10/50 μM. BP100 inhibited bacterial multiplication and significantly decreased X. arboricola pv. pruni population levels and disease severity on Prunus GF-677 leaves when applied in preventative and curative strategies. The persistence of BP100 activity on plant surface lasted up to five days, being optimal 24-48 h before pathogen inoculation. A 48 h post-infection effect of BP100 was also observed. These results demonstrate the ability of antimicrobial peptides to reduce pathogen epiphytic populations to levels below the minimum infective concentration, and thus to prevent infections.