Induction of defense responses and protection of almond plants against Xylella fastidiosa by endotherapy with a bifunctional peptide

Xylella fastidiosa is a plant pathogenic bacterium that has been introduced in the European Union (EU), causing significant yield losses in economically important Mediterranean crops. Almond leaf scorch (ALS) is currently one of the most relevant diseases observed in Spain, and no cure has been found to be effective for this disease. In previous reports, the peptide BP178 has shown a strong bactericidal activity in vitro against X. fastidiosa and to other plant pathogens, and to trigger defense responses in tomato plants. In the present work, BP178 was applied by endotherapy to almond plants cv. Avijor using preventive and curative strategies. The capacity of BP178 to reduce the population levels of X. fastidiosa and to decrease disease symptoms, and its persistence over time were demonstrated under greenhouse conditions. The most effective treatment consisted of a combination of preventive and curative applications and the peptide was detected in the stem up to 60 days post-treatment. Priming plants with BP178 induced defense responses mainly through the salicylic acid pathway, but also overexpressed some genes of the jasmonic acid and ethylene pathways. It is concluded that the bifunctional peptide is a promising candidate to be further developed to manage ALS caused by X. fastidiosa. Overall design: The transcriptome of Prunus dulcis cv Avijor plants treated by a combination of spray and endotherapy applications of the peptide BP178 were compared to non-treated ones 24h post-treatment. Four biological replicates were used. Each biological replicate consisted of 5 plants.