Study on the In vitro and In vivo antifungal activities of nano-silver against Mycoleptodiscus indicus causing leaf blight on lotus in Vietnam

Lotus, Nelumbo nucifera Gaertn is Vietnam's symbol and Buddhism's flower and plays an essential part in rural Vietnam's economy as all aspects of lotus could bring benefits to farmers. But, unfortunately, lotus yield in Vietnam is seriously affected by various plant diseases. Among them, leaf blight is currently emerging as one of the primary diseases devastating lotus crops in Vietnam, in which there are large necrotic parts on lotus leaves, flowers and seeds.

Aloe barbadensis extract was used for synthesizing silver nanoparticles. Leaf blight lotus leaves were collected to isolate pathogenic fungi-infection of isolated pathogenic fungi on the healthy lotus and then identify hidden mold by 28S rRNA sequencing. Determination of in vitro minimal inhibition concentration of nano-silver was conducted according to Azizi. The reduction of disease symptoms and biological characteristics of the treated lotus was observed.

Morphological analysis and molecular identification of 28S rRNA sequencing showed that the pathogenic microorganism was Mycoleptodiscus indicus (M. indicus). Both in vitro antifungal activity and in vivo treatment of leaf blight lotus using a nano-silver solution showed that 30 ppm of nano-silver was the minimal inhibition concentration (MIC) for totally eradicating M. indicus growth. This was the first time M. indicus was reported to infect and cause leaf blight on a lotus. Previously, M. indicus was a well-known plant pathogen that could cross-kingdom infect humans and animals. Thus, the fact that lotus is widely cultured in Vietnamese rural could increase the chance for M. indicus to spread; hence, this raised the alarm about its potential harm to plants, humans and animals. And, significantly, it revealed nano-silver as a possible approach to prevent M. indicus.