Control of Bacterial Canker caused by Pseudomonas syringae pv. actinidiae (Psa) in kiwifruit plants by resinous exudates and extracts of Adesmia balsamica

BACKGROUND: Pseudomonas syringae pv. actinidiae (Psa) is the pathogen responsible for kiwifruit's bacterial canker, which produces signi cant economic losses. Effective treatments and measures to control this disease have not yet been found; it is currently controlled with many products containing heavy metals (especially copper) or antibiotics (especially streptomycin), which can cause serious phytotoxicity and antibacterial resistance problems. Therefore, it is essential to develop new strategies to control this disease by obtaining a product of natural origin of sustainable use, which is biodegradable and nontoxic to the environment, that could be used as biopesticide. RESULTS: The ethyl acetate extract of Adesmia balsamica and the compound 20,40-dihydroxychalcone (2,4-DHCH; 4) exhibited the same or similar antibacterial activity, respectively, as the positive control (commercial pesticide) at an effective concentration of 500 ∼g mL−1, on kiwifruit plants (Soreli variety) in vivo. Fluorescence microscopy revealed that one of the main modes- of-action by which it inhibits bacterial growth of Psa is by increasing membrane permeation, causing its disruption and intracellular alteration. Additionally, the application of the extract and 4 manages to control Psa bacterial canker disease by reducing gene expression related to the hrp W gene; Psa concentratiosn were speci cally detected through real-time quantitative polymerase chain reaction (qPCR). CONCLUSION: The ethyl acetate extract of A. balsamica effectively controls Psa in vitro and in vivo applied on kiwifruits plants, and therefore is a potential biopesticide for the control of bacterial canker in kiwifruit and potentially other crops.