Tomato (Lycopersicon esculentum L.) is an economically important food crop grown worldwide. Bacterial wilt, caused by Clavibacter michiganensis subsp. Michiganensis (Cmm), affects tomato plants, causing harmful impacts and significant losses in crop yield. Defensin priming has previously revealed great potential in the biological control of plant diseases. The present study aimed to exogenously apply defensin to tomato plants grown in hydroponic culture in order to investigate its key role in enhancing resistance to bacterial wilt. The results revealed that Cmm infection significantly reduced the relative water content, gas exchange attributes, minerals uptake and contents of photosynthetic pigments, soluble sugars and proteins in tomato plants, as compared to control plants. Moreover, Cmm infection induced the levels of total phenols, flavonoids, glycine betaine, proline, malondialdehyde, hydrogen peroxide, electrolyte leakage, ascorbate, oxidized ascorbate, reduced glutathione, antioxidant enzymes (SOD, APX, CAT) and antioxidant genes expressions in tomato plants. On the other hand, defensin treatment significantly reduced disease severity index and oxidative stress markers in Cmm-infected tomato, as compared to Cmm-infected plants. Moreover, defensin treatment significantly enhanced the relative water content, gas exchange attributes, minerals uptake and levels of photosynthetic pigments, soluble sugars, soluble proteins, total phenols, flavonoids, glycine betaine, proline, ascorbate, oxidized ascorbate, reduced glutathione, antioxidant enzymes and antioxidant genes expression in leaves of Cmm-infected tomato, as compared to Cmm-infected plants. Taken together, the present study introduced defensin treatment as a natural, safe, and eco-friendly approach to induce the biological control of bacterial wilt in tomato plants.
Key words: Tomato; soilless agriculture; defensin treatment; bacterial wilt; antioxidants; genes expression.
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