Isolation, Identification, and Control of Pathogenic Endophytic Fungi in Nymphaea candida Presl Tissue Culture

<i>Nymphaea candida</i> Presl is a rare hardy water lily at risk of extinction and has been included on the 'Red List' of threatened species of the International Union for the Conservation of Nature. To protect germplasm resources and propagate <i>N. candida</i> seedlings, this study conducted tissue culture and found that pathogenic endophytic fungal infection was the main reason for failure of tissue culture. Compared with the stems and leaves, the roots of <i>N. candida</i> had the highest rates of fungal infection during tissue culture. Subsequently, three isolated endophytic fungi, <i>Fusarium oxysporum</i>, <i>Phytopythium helicoides</i>, and <i>Alternaria</i> sp., showed the highest frequency of occurrence in tissue culture. Furthermore, an antifungal formulation comprising 0.1 μg/mL pyrimidin suspension, 1 μg/mL mancozeb wettable powder, and 1 μg/mL carbendazim was constructed and could reduce the infection rates of root and stem tissues to 7.5% and 0%, respectively. Finally, the usefulness of this antifungal formulation for inhibition of endophytic fungi in tissue culture of <i>N. candida</i> was validated. This study not only provides important technical support for mass production of seedlings of <i>N. candida</i>, but also provides a scientific reference for the protection of endangered aquatic plant species.