Isolation, Identification, and Management Strategies for the Root Rot Pathogen of Cardamine violifolia

Root rot disease severely impacts the yield of Cardamine violifolia, a selenium-enriched cruciferous vegetable. However, the causal pathogens and effective control strategies of this disease remain poorly characterized. This study systematically isolated and identified three key pathogens from diseased tissues in the Enshi region: Aspergillus costaricensis, Mucor circinelloides cf. lusitanicus, and Fusarium pernambucanum. Morphological characterization, phylogenetic analysis, and pathogenicity testing were conducted. Candidate fungicides were screened using plate inhibition assays, and combinations were optimized and validated through soil drenching experiments. While propiconazole showed broad-spectrum activity, its efficacy against Aspergillus and Mucor was suboptimal. A novel ternary compound fungicide, T10, combining propiconazole, hymexazol, and difenoconazole, demonstrated significantly enhanced potency with EC50 values of 7.313, 12.2983, and 0.1781 mg/L against the three pathogens, representing reductions of 66.0%, 77.7%, and 92.1% compared to the most effective single application of propiconazole. At 10 mg/L, T10 increased inhibition rates by 62.62%, 77.53%, and 20.85% against the three pathogens, respectively, compared to propiconazole alone. Propidium iodide (PI) staining revealed increased cell membrane permeability in T10-treated pathogens, suggesting that membrane damage may contribute to its antifungal effect. This study provides a robust scientific basis for sustainable disease management of this high-value selenium-enriched vegetable crop.