Molecular Pathogens, 2025, Vol.16, No.4, 193-206 http://microbescipublisher.com/index.php/mp 194 findings lay the foundation for in-depth elucidation of the molecular mechanisms of cucumber disease resistance and also provide genetic resources for disease-resistant breeding. In the study, the discussion was conducted on the hormone regulation and genetic mechanism of cucumber disease resistance: the infection mechanism of the main pathogens on cucumber is introduced, and the role of phytohormones such as salicylic acid, jasmonic acid, and ethylene in the response to cucumber disease, the interaction between these hormone signals and the integration with environmental factors. Next, the identification and function of cucumber disease-resistant genes, the regulatory role of transcription factors, and the participation mechanism of non-coding RNA are summarized, and the role of epigenetic regulation in cucumber disease-resistant is discussed. Taking the resistance of cucumber to powdery mildew as a case, we will conduct in-depth analysis of examples of the coordinated regulation of disease resistance between hormones and genetic factors. Through the review of this study, we summarize the research progress in this field in recent years, aiming to provide a theoretical basis for improving the efficiency of cucumber disease resistance and formulating comprehensive disease prevention and control strategies. 2 The Main Types and Infectious Mechanisms of Cucumber Pathogens 2.1 Fungal diseases: powdery mildew, downy mildew Powdery mildew and downy mildew are two major fungal diseases that harm cucumber production. Powdery mildew is caused by the fungus of the genus Podosphaera xanthii, etc., and the typical symptom is the appearance of white powdery mold spots on the surface of the leaves, which then yellow and dry the leaves (Bandamaravuri et al., 2020). Powdery mildew pathogens are exogenous parasitics, and the mycelium attaches to the host surface and invades epidermal cells to absorb nutrients. Powdery mildew spreads rapidly and is very likely to spread under warm and dry environments. Downy mildew is caused by oomycosis (Pseudoperonospora cubensis), which mainly infects leaves. In the early stage of the disease, water-stained pale green spots appeared on the front of the leaves, and gray-black mold grew on the back. The lesions quickly expanded and connected into pieces, resulting in yellow and curling leaves (Schouten et al., 2014). Downy mildew bacteria are obligate parasitics, which produce zoospora and spread through wind and rain, and are prone to outbreaks and epidemics under high humidity conditions. The resistance of powdery mildew and downy mildew on cucumbers is mostly genetic in quantity and is controlled by multiple loci. According to research, the resistance of different cucumber materials to powdery mildew and downy mildew varies significantly from the seedling stage to the plant stage. There are high resistance resources in some wild relatives (such as cucumbers) that can be used for disease-resistant breeding of cucumbers (Akhtar et al., 2020). 2.2 Bacterial diseases: keratinous disease, etc. Bacterial keratinosis is the most representative of cucumber bacterial diseases, and is caused by Pseudomonas syringae pv. lachrymans (Zhang et al., 2019). This disease mainly infects the leaves, and the water-like light green spots are formed in the early stage, and the spots turn into brown horn spots in the later stage. In severe cases, multiple lesions fuse, causing the leaves to dry and perforate. The keratopathy bacteria can survive on seeds and sick bodies, spread through wind and rain, and invade from stomata or wounds. High temperature and high humidity conditions are conducive to the prevalence of keratopathy. Field surveys show that there are differences in resistance to diagonal tract disease in different cucumber varieties, but there are fewer high resistance resources. The currently reported materials for horny resistant keratinous diseases are mostly derived from wild cucumbers or related relatives, and disease-resistant genes can be introduced into cultivars through hybridization. The resistance to keratinous lesions is often quantitatively inherited. Studies have located the main effect QTL site of cucumber anti-keratinous lesions on the second chromosome. In order to prevent and treat keratopathy, in addition to breeding disease-resistant varieties, the use of seed treatment, crop rotation, and protective ground humidity control in agriculture can also reduce its occurrence (Słomnicka et al., 2021). 2.3 Viral diseases: cucumber mosaic virus (CMV) and cucumber green mosaic virus (CGMMV) Cucumbers are susceptible to a variety of plant viruses, among which cucumber mosaic virus (CMV) and
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