Antifungal Gallotannins in Mango (Mangifera indica): Distribution in Aerial Tissue and Role in Anthracnose Resistance

Abstract

Aims: The present study investigated the presence of antifungal Gallotannins in aerial parts of the mango tree; namely florets, young flush and mature leaves which are also subjected to diseases such as anthracnose. The decline of gallotannin activity in fruit peel and the correlation with anthracnose lesion expansion in inoculated fruit was also investigated Study Design:  The experiment was performed twice using three replicates per each trial. Data were analyzed for variance in a completely randomized design. Methodology: Florets, flush and mature leaves were collected from cultivar ‘Kohu’. Fruits of cultivar ‘Karutha colomban’ which is resistant to anthracnose were used for inoculation of fruits with conidia of Colletotrichum gloeosporioides. Disease development was assessed daily by measuring lesion diameter. Peel of fruits were also obtained to extract antifungal compounds on day 1, 3, 5, 7 and 9 after harvest. Extraction of antifungal compounds from leaves, flush, florets or fruit peel was done using vacuum infiltration method with dichloromethane and methanol (1:1) as the extraction solvents. The extract was evaporated to dryness using a rotory evaporator and the dry residue was used in TLC bio-assay. The amount of Gallotannin antifungal activity was assessed by obtaining the inhibition area at Rf. 0.00 on thin layered chromatography plates (TLC). Results: The amount of gallotannins as seen by the inhibition area on TLC bio-assay is significantly (P = .05) higher in florets (285±29.29) and unripe fruit peel (256.66±29.48) when compared with vegetative leaves (111.67±4.4). The amount of gallotannins in fruit peel declined by approximately 20% by the time anthracnose lesions initiated. Conclusion: Not only mango fruit peel, but mango florets, flush and mature leaves also contain antifungal gallotannins.