Molecular Pathogens, 2025, Vol.16, No.4, 193-206 http://microbescipublisher.com/index.php/mp 195 cucumber green mosaic virus (CGMMV) are two important viral diseases. Cucumber mosaic virus disease is caused by CMV, which has a very wide host range and spreads rapidly in the fields through aphid sucking. Once infected, the cucumber plant shows significant mottled flowers and leaves, curly new leaves, and deformity, and its growth and development are hindered. Since CMV is an RNA virus, it mutations quickly and has no effective chemical agents, it mainly relies on disease-resistant varieties and aphid prevention measures in prevention and treatment (Monnot et al., 2022). Cucumber green mosaic virus disease is caused by CGMMV and is an important virus with quarantine significance. CGMMV can be transmitted through seeds, with hidden transmission routes and fast transmission speed. The leaves of the affected plants have mottled flowers and leaves with different thicknesses, and the surface of the fruits has become corrugated and green mottled patterns appear, which reduces the value of the product. CGMMV poses great threat to cucumber production, especially in greenhouse cultivation, which is prone to accumulation and outbreaks. Since CGMMV belongs to the genus of mosaic virus, its genome is stable, disease-resistant breeding has become the fundamental strategy for preventing and treating the disease (Miao et al., 2021). 3 The Role of Plant Hormones in Cucumber's Disease Resistance 3.1 Salicylic acid (SA) and system acquired resistance (SAR) Salicylic acid (SA) is the first known plant disease-resistant signaling molecule and plays a key role in the fight against biological infection. Numerous studies have shown that the increase in SA levels and activation of signaling pathways can enhance the resistance of plants (especially dicots) to biological pathogens. In cucumbers, pathogenic infestation can induce local and whole-short accumulation of SA, thereby initiating systemic acquired resistance (SAR). SAR is a broad-spectrum and long-lasting resistance state. After a certain part of the plant is attacked by a pathogen, the rest of the plant also shows high resistance to different pathogens. SA is considered the core mediator of SAR: After local infection of the host plant, SA or its metabolites (such as methyl salicylate) are transported through the phloem, transmitting resistance signals to distal tissues, triggering defense response gene expression. For example, SA can induce the large expression of disease-related proteins (PR genes, such as PR1) in cucumbers. These PR proteins have antibacterial and antifungal activities and can improve the overall disease resistance of the plant. In addition, SA is also involved in local resistance mechanisms such as triggering allergic reactions (HR), whose accumulation is often accompanied by oxidative outbreaks and programmed cell death to limit pathogen expansion (Pazarlar et al., 2021). 3.2 Jasmonic acid (JA) and pest resistance Jasmonic acid (JA) and its derivatives (such as methyl jasmonate MeJA) are signaling molecules that play an important role in plants in coping with harm and necrotic pathogens. It is generally believed that the JA signaling pathway mainly mediates resistance to chewy insects and necrotic trophic pathogens, and is often functionally antagonistic to the SA pathway. In cucumbers, the increase in JA levels and upregulation of related gene expression are closely related to increased resistance to some diseases (Wang et al., 2024). Studies have found that exogenous spraying of a certain concentration of methyl jasmonate can induce increased activity of defense-related enzymes in cucumbers in body and improve their resistance to powdery mildew. JA signaling also involves the resistance of cucumber to certain diseases and insect pests, such as in the cucumber's response to root knot nematode infection, where the JA pathway is activated to promote thickening of cell walls and the production of anti-worm proteins. The molecular basis of JA's action is to regulate the expression of related defense genes (including protease inhibitors, phytoprotein secondary metabolites synthases, etc.) to limit pathogen feeding and expansion. Key components in the cucumber JA signaling pathway include receptor COI1, transcription factor MYC2, etc. When cucumbers are invaded by pests, the active jasmonic acid-Ile in the cell binds to the COI1 receptor, prompting the degradation of JA pathway inhibitor JAZ protein, releasing the transcription factor MYC2 and others to initiate defense gene expression (Liu et al., 2023; Wang et al., 2024). Research reports that cucumber
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