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

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.