Suppression of Melanose Caused by Diaporthe citri on Citrus Leaves Pretreated with Bio-sulfur

• Main Authors: Yong Ho Shin, Eun Ju Ko, Su Jeong Kim, He Nam Hyun, Yong Chull Jeun
• Format: Article
• Language: English
• Published: Hanrimwon Publishing Company 2019-10-01
• Series: The Plant Pathology Journal
• Subjects: environment friendly; fluorescence microscope; infection behavior; scanning electron microscope
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6788406

Melanose, caused by Diaporthe citri, is one of severe diseases in citrus, a major economic resource in Jeju island. To reduce the usage amount of organic synthetic fungicide, bio-sulfur was tested as an alternative chemical to control citrus melanose in the present study. Direct antifungal activity of bio-sulfur against D. citri was determined through in vitro experiment using artificial nutrient media. Disease severity of melanose on bio-sulfur pretreated citrus leaves was lower than that on untreated ones. To illustrate the mechanism of disease suppression by bio-sulfur, infection structures were observed with a fluorescent microscope and a scanning electron microscope. In fluorescent microscopic observation, most conidia rarely germinated. In addition, hyphal growth on leaves pretreated with bio-sulfur was inhibited compared to that on untreated ones. In scanning electron microscope images of bio-sulfur pretreated leaves, surfaces of most conidia were shrunk while hyphae were morphologically changed and frequently branched. Such microscopic observations were also found for leaves pretreated with a commercial fungicide Dithianon. These results suggest that bio-sulfur may be used to control citrus melanose as an environment friendly alternative to organic synthetic fungicides