Fruit brown rot caused by Neoscytalidium dimidiatum on Selenicereus monacanthus in the Philippines

Abstract

Multiple fungal pathogens infect economically important fruits, thereby affecting their quality and marketability. Previous research showed that some fungal pathogens that can infect the stems might infect the fruit but show a different symptom. To determine the causal pathogen of a fruit disease of Selenicereus monacanthus (Dragon fruit), we used a combination of fungal pathology characterization and molecular biology techniques. This paper presents the pathogenicity of Neoscytalidium dimidiatum MBDF36C to S. monacanthus resulting in brown rot and canker on fruits and stem, respectively. The paper also demonstrates the in vitro inhibition of N. dimidiatum MBDF36C by chemicals, including a bio-fungicide containing Bacillus subtilis. At seven days post-inoculation, we observed severe browning on N. dimidiatum MBDF36C-inoculated fruits but not on stems. Stems exhibited canker-like symptoms. The same fungus was re-isolated from both inoculated diseased fruits and stems, thereby confirming Koch's postulates. The pathogen was identified as N. dimidiatum based on its morphology, cultural characteristics, and sequences of the partial ß-tubulin gene. In vitro growth of N. dimidiatum MBDF36C was also completely inhibited by a bio-fungicide containing B. subtilis, isoprothiolane, and mancozeb. This study is the first report of N. dimidiatum causing brown fruit rot of dragon fruit in the Philippines. This information could impact the current postharvest fruit handling operations and future studies on dragon fruit disease management