Molecular Soil Biology 2025, Vol.16, No.2, 73-82 http://bioscipublisher.com/index.php/msb 75 2022). In addition, stem rot of Sclerotinia sclerotiorum also occurs from time to time, which can lead to stem rot, plant lodging and significant yield loss (Jiang et al., 2013). 2.2 Factors contributing to disease outbreaks Warm and humid environments create ideal conditions for disease development. Powdery mildew thrives in warmth, while downy mildew needs high humidity for spore germination and spread. Poor ventilation and improper water management can also make diseases worse (Moparthi et al., 2017). Diseases spread through several routes—airborne spores, contaminated water, and infected soil. Using infected seeds or plant material increases the risk of long-term pathogen presence. Pathogens like Podosphaera xanthii show genetic variability, making them harder to control and more likely to overcome plant resistance (Liang et al., 2018). 2.3 Impact on yield and medicinal quality During off-season cultivation, frequent disease outbreaks cause a significant rise in plant death rates, especially with root rot or severe powdery mildew. In heavily infected fields, mortality can exceed 90%, resulting in serious economic losses for growers (Sun et al., 2022). Diseases also reduce the synthesis of key secondary metabolites such as leonurine, lowering medicinal quality. Powdery mildew and downy mildew interfere with photosynthesis and nutrient absorption, while root rot blocks water and nutrient uptake. These combined effects lead to a clear decline in the plant’s medicinal value (Yang et al., 2008; Jia et al., 2010; Cho et al., 2013). 3 Key Issues in Off-Season Cultivation of Leonurus japonicus var. hunanensis 3.1 Environmental conditions in off-season cultivation Off-season cultivation of L. japonicus var. hunanensis is usually carried out in greenhouses or plastic tunnels. These controlled environments extend the growing season and allow flexible scheduling but also create conditions that favor disease outbreaks. High humidity, poor ventilation, and large temperature differences between day and night are common in greenhouses. These conditions are ideal for fungal pathogens such as Podosphaera xanthii (causing powdery mildew) and Fusarium spp. (causing root rot). High humidity, in particular, speeds up spore germination and fungal growth, increasing disease pressure (Liang et al., 2018). The timing of disease and pest outbreaks is closely linked to specific features of off-season systems. For example, high planting density, used to maximize yield, can promote pathogen spread and raise infection rates. Large fluctuations in temperature between day and night can weaken plant defenses, making them more vulnerable to infections. These environmental stresses and cultivation practices interact, showing the need for targeted strategies in off-season disease management (Sun et al., 2022). Techniques like LED light treatments have been shown to improve yield and quality under low-season growing conditions (Lee et al., 2023). 3.2 Technical challenges in off-season cultivation At present, the most troublesome problem of Off-season Cultivation is that the disease is not easy to control and the control cost is high. Although the use of pesticides, fungicides and other chemical means is common, frequent spraying not only costs money, but also easily makes the bacteria resistant. Sometimes, drug residues are left, which is not conducive to the safety and sales of medicinal materials (moparthi et al., 2017). Another problem is the disjunction between the research and practical application of disease resistant germplasm. Although many resistant materials have been found by molecular markers and other methods, these achievements are rarely used in actual production. Many greenhouses are still under traditional manual management, and environmental control and pest control are not accurate enough. Advanced technologies such as automatic temperature and humidity regulation system and IPM (Integrated Pest Management) are not used much, which leads to frequent occurrence of diseases. To truly solve these problems, we need to combine the breeding of disease resistant materials with advanced cultivation methods, and work together from seed source to management (Gu et al., 2010).
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