In-Vitro Antifungal Effect of Guava (Psidium Guajava), Watercress (Nasturtium Officinale) and Soursop (Annona Muricata) Plant Extracts on Soft Rot Fungal Pathogen of Ginger, Fusarium Solani

Chen, Hui Teng (2023) In-Vitro Antifungal Effect of Guava (Psidium Guajava), Watercress (Nasturtium Officinale) and Soursop (Annona Muricata) Plant Extracts on Soft Rot Fungal Pathogen of Ginger, Fusarium Solani. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Ginger (Zingiber officinale) is an important crop utilized in cooking and traditional medicine. The most devastating disease that infects ginger is rhizome rot disease caused by pathogenic fungi like Fusarium oxysporum, Fusarium solani and Pythium sp. Management options are available but are mainly chemically cantered i.e., carbendazim and mancozeb fungicides. However, these chemicals are teratogenic and may leach into surrounding bodies of water to cause environmental issues. In hydroponic cultivation, these harmful fungicides would be deposited at the planting medium and ginger rhizomes. Objectives of this study were to isolate Fusarium sp. from hydroponically cultivated ginger and explore the potential of guava, watercress and soursop plant extracts in suppressing fungus causing ginger soft rot. Isolation of Fusarium sp. was performed using ginger rhizome displaying soft rot symptoms. Pure culture of Fusarium sp. was identified via colony morphology and spore characteristics. Leaf samples obtained from a fruit orchard at Manchis, Bentong were subjected to extraction using ethanolic, methanolic and hydrodistillation methods. Plant extracts obtained were used for inhibition tests against isolated fungus using the disc-diffusion method. PDA plates containing 0.005% chloramphenicol antibiotics were inoculated with 100μL of fungal spore suspension (1×106 spores/ml) by spread plate. Filter paper discs (5mm diameter) infused with guava leaf extract at concentrations ranging from 1,000-14,000 ppm, watercress extract at concentrations of 1,000-600,000 ppm and soursop extract at concentrations of 1,000-200,000 ppm were tested against fungus. Negative controls (water and DMSO) and positive controls (mancozeb and hexaconazole) were included. All extracts did not show inhibition against the growth of Fusarium sp., after 7 days of incubation in contrast with positive control. Triplicates of each inhibition test were carried out. Although inhibition was not observed in-vitro using crude extracts, purification of crude extracts and quantification of active compounds are suggested for future research. Isolated fungal pathogens were further identified via DNA sequencing with confirmed identification of Fusarium falciforme and F. solani. Pure isolates will be kept as stock culture for future research. Keywords: Psidium guajava, Nasturtium officinale, Annona muricata, ginger soft rot, Fusarium solani, botanical fungicides