Control of rubus stunt and stolbur diseases in Madagascar periwinkle with mycorrhizae and a synthetic antibacterial peptide

Abstract

Three experimental treatments consisting of inoculation with an arbuscular mycorrhizal fungus, application of a synthetic antimicrobial peptide or application of a resistance inducer, were evaluated in Madagascar periwinkle as control methods for rubus stunt and stolbur diseases caused by 'Candidatus Phytoplasma rubi' and 'Candidatus Phytoplasma solani', respectively. Two experiments were conducted under controlled environment conditions. In the first experiment, 4 months after graft-inoculating the phytoplasmas, the root colonization achieved by Rhizophagus irregularis significantly reduced both disease symptoms and the frequency of detection of the pathogens by real-time PCR. In the second experiment, the antimicrobial peptide BP100 totally prevented disease symptoms, despite the molecular detection of the phytoplasmas in 75% and 50% of the plants inoculated with 'Ca. Phytoplasma rubi' and 'Ca. Phytoplasma solani', respectively, and was more effective than benzothiadiazole (BTH) at increasing resistance against the pathogenic infections. A potential combination of early mycorrhizal inoculation and BP100 antimicrobial peptide application is envisaged as a future control strategy for phytoplasma diseases.

Screening and identification of BP100 peptide conjugates active against Xylella fastidiosa using a viability-qPCR method

“…So, their antibacterial activity and their availability for being expressed in plants make AMPs good candidates for the control of this plant pathogen, either using transgenic expression or other delivery strategies such as endotherapy. In the present study, a set of 11 peptide conjugates derived from the lead peptide BP100 and a fragment of cecropin, magainin or melittin, previously reported by our group as active against several plant pathogenic bacteria and with low toxicity to eukaryotic cells (moderate to low hemolysis) (Table 3) [10,17,20], were screened for their activity against Xf. One of these peptide conjugates (BP178) has been produced in transgenic rice [18,19], and has also been tested in vitro against Xf and other plant pathogens showing high antibacterial activity [17,21].…”

“…vesicatoria, Pseudomonas syringae pv. syringae and Erwinia amylovora, were low haemolytic, and were able to control infections in plant hosts caused by these bacteria or even due to phytoplasms [10,17,20]. In the case of Xf, only BP178 has been tested in vitro, showing high antibacterial activity against a collection of Xf strains.…”