Molecular Pathogens, 2025, Vol.16, No.4, 193-206 http://microbescipublisher.com/index.php/mp 193 Feature Review Open Access Hormonal and Genetic Control of Cucumber Responses to Pathogens Hongwei Liu 1, Shiying Yu2 1 Tropical Microbial Resources Research Center, Cuixi Academy of Biotechnology, Zhuji, 311800, Zhejiang, China 2 Biotechnology Research Center, Cuixi Academy of Biotechnology, Zhuji, 311800, China Corresponding author: shiying.yu@cuixi.org Molecular Pathogens, 2025, Vol.16, No.4 doi: 10.5376/mp.2025.16.0020 Received: 29 Jun., 2025 Accepted: 11 Aug., 2025 Published: 26 Aug., 2025 Copyright © 2025 Liu and Yu, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Liu H.W., and Yu S.Y., 2025, Hormonal and genetic control of cucumber responses to pathogens, Molecular Pathogens, 16(4): 193-206 (doi: 10.5376/mp.2025.16.0020) Abstract Cucumbers (Cucumis sativus) is an important vegetable crop widely cultivated worldwide, but its production is often threatened by diseases caused by infection by multiple pathogens. Common cucumber diseases include mycotic diseases, bacterial diseases and viral diseases, which can lead to severe loss of yield and quality. Plant hormone signaling and disease-resistant related genes play a key role in cucumber's disease-resistant immunity and are currently hot topics in plant pathology and molecular breeding research. This study reviews the research progress on the hormone regulation mechanism and genetic basis of cucumber disease resistance in recent years, explores the role of plant hormones such as salicylic acid, jasmonic acid, and ethylene in the cucumber disease resistance response, analyzes the interaction and network integration between different hormone signals, as well as the molecular regulatory mechanisms of disease-resistant genes, transcription factors, non-coding RNA and epigenetic modifications on cucumber disease resistance. On this basis, powdery mildew is used as an example to deeply explain the hormone and genetic regulatory mechanisms of cucumber's disease resistance, and looks forward to the application prospects of using molecular breeding and gene editing technologies to improve cucumber's disease resistance. Through this study, we hope to provide reference for the research on the mechanism of disease resistance of cucumber and disease resistance breeding practice. Keywords Cucumber; Plant hormones; Signaling; Disease-resistant genes; Epigenetics 1 Introduction Cucumber is one of the top cash crops in the world with a planted area and output. The global cucumber and gherkin production in 2022 will be about 94 million tons, of which China accounts for more than 80%. Cucumbers play an important role in vegetable supply and nutritional diet. However, cucumbers are susceptible to infection by a variety of pathogens, common diseases include powdery mildew and downy mildew caused by fungi, keratinous tract disease caused by bacteria, and mosaic diseases caused by viruses. These diseases seriously affect the yield and quality of cucumbers. Viral diseases such as cucumber mosaic virus disease (CMV) and cucumber green mosaic virus disease (CGMMV) have the characteristics of fast transmission and short latent period, which often leads to systemic mosaic, deformity and plant weakness, which poses great threat to yield (Shi et al., 2018). With people paying attention to food safety and sustainable production, adopting the plant's own anti-disease mechanism to prevent and control diseases has become an important research direction. Plants are mainly dependent on the innate immune system against pathogen infection, including two levels: pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) (Oh et al., 2014). In the immune response process, plant hormone signal plays a core regulatory role, and signaling pathways mediated by different hormones (such as SA, jasmonic acid JA, ethylene ET, etc.) together form a complex disease-resistant network. In addition to hormone signals, the plant's own disease-resistant genes also play a key role in the immune response. Disease-resistant genes (R genes) can directly or indirectly identify pathogenic effectors, triggering downstream defense responses; mutations in some susceptible genes (S genes) can confer lasting broad-spectrum disease resistance to plants. In recent years, with the development of sequencing technology and functional genomics, a large number of cucumber disease-resistant QTLs and related genes have been localized and cloned, such as several recessive QTL sites that resist downy mildew, the main-acting sites that resist powdery mildew and the susceptibility gene CsMLO1/CsMLO8, and the key gene that resists blight, CsChi23, etc. (Nie et al., 2015). These
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