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Positive interaction between melatonin and methyl jasmonate enhances Fusarium wilt resistance in Citrullus lanatus

Summary

Researchers discovered that two natural plant signaling molecules, melatonin and methyl jasmonate, work together to protect watermelons from a devastating fungal disease called Fusarium wilt. When applied to watermelon plants at the right concentrations, these molecules trigger the plant’s natural defense mechanisms, making the plants more resistant to infection. The study shows these compounds can be used as natural, sustainable alternatives to chemical pesticides for protecting crops.

Background

Fusarium wilt, caused by the soil-borne fungal pathogen Fusarium oxysporum, is a devastating disease affecting numerous agricultural crops including watermelon. Melatonin has emerged as a potential enhancer of plant resistance against fungal pathogens, but the underlying mechanisms remain unclear. This study investigates the interaction between melatonin and methyl jasmonate in enhancing watermelon resistance to Fusarium oxysporum f. sp. Niveum race 2 (FON2).

Objective

To elucidate the mechanisms by which melatonin and methyl jasmonate (MeJA) interact to enhance watermelon resistance against FON2 infection. The study examines the dose-dependent effects of these signaling molecules, their reciprocal regulatory relationships, and the involvement of defense-related enzymes and secondary metabolites.

Results

Optimal melatonin (10 μM) and MeJA (1 μM) concentrations reduced FON2 disease incidence by 75.8% and 70.0%, respectively. Melatonin upregulated MeJA synthesis genes (LOX1, AOC1) and increased MeJA content, while MeJA reciprocally promoted melatonin accumulation through upregulation of ClCOMT1. Both compounds inhibited FON2 mycelial growth dose-dependently and enhanced activities of polyphenol oxidase, phenylalanine ammonia lyase, and lignin accumulation upon infection.

Conclusion

Melatonin and MeJA form a reciprocal positive regulatory loop that enhances watermelon resistance to FON2. Melatonin induces MeJA synthesis, which provides feedback to promote melatonin accumulation, and both compounds upregulate defense enzymes and lignin biosynthesis. This mechanism offers sustainable alternatives to chemical pesticides for managing Fusarium wilt.
  • Published in:Frontiers in Plant Science,
  • Study Type:Experimental Study,
  • Source: PMID: 40376169, DOI: 10.3389/fpls.2025.1508852
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