A newly published study in Physiology and Molecular Biology of Plants reveals that silicon (Si) acts as a powerful defense priming agent in tomato, enabling susceptible cultivars to mount stronger resistance against early blight, a destructive disease caused by Alternaria solani. Using the cultivar ‘Karoon’, the research team demonstrated that Si supplementation not only reduced disease severity and lesion expansion but also preserved photosynthetic activity and overall plant growth.
The authors show that Si triggers a coordinated reprogramming of plant immune signaling, beginning with an early but short-lived activation of salicylic acid (SA) responses. This is followed by a dominant switch to jasmonic acid (JA) and ethylene (ET) pathways, which are more effective against necrotrophic pathogens like A. solani. Si-treated plants accumulated significantly higher JA and ET levels by 7 days post infection, while SA levels declined faster compared to untreated plants.
At the molecular level, Si fine-tuned the expression of several key defense genes, including WRKY70, PR1, PR3, LOX, PAL, and ACS2, enabling plants to overcome the typical antagonism between SA and JA pathways. These transcriptional shifts were supported by strong induction of antioxidant enzymes and higher levels of protective metabolites such as phenolics, flavonoids, glutathione, and ascorbate.
Multivariate analysis revealed that Si-treated infected plants form a distinct physiological and molecular profile, characterized by lower oxidative stress, enhanced JA/ET-driven defense signatures, and better maintenance of growth performance.
The study concludes that silicon serves as an effective, non-toxic priming agent capable of restructuring immune signaling networks, reducing disease damage, and supporting metabolic stability. This positions Si as a promising component for the sustainable management of early blight in tomato.
Reference
Joybari, F.M., Dehpour, A.A. & Eslami, B. Silicon-mediated priming of SA–JA crosstalk enhances systemic resistance to Alternaria solani in susceptible tomato via WRKY-directed defense gene reprogramming. Physiol Mol Biol Plants (2025). https://doi.org/10.1007/s12298-025-01682-3
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