Antifungal Activity of Some Natural Plant Extracts Against Causal Agent of Anthracnose Disease of Chilli

Abstract

Anthracnose caused by Colletotrichum species is a common postharvest disease of chilli fruit in Sri Lanka. The aim of the study was to isolate the chilli anthracnose disease causing Colletotrichum species and control the organisms by the application of natural plants extracts. Two Colletotrichum isolates ISO 1 and ISO 2 were isolated from chilli anthracnose diseased fruits and they were identified as Colletotrichum capsici and Colletotrichum gloeosporioides respectively based on the morphological features. Crude extracts of five spices, viz. Cassia sp., Lantana sp., Ricinus sp., Cinnamomum sp., and Catharanthus sp. were made using cold water, hot water and ethanol extraction and they were tested for their anti-fungal effects against the two Colletotrichum isolates isolated from chilli anthracnose diseased fruits. Pathogenic variations of the fungal isolates in terms of pathogenicity and virulence were determined by In vitro inoculation assays using healthy chilli fruits. All five spices studied showed significant anti-fungal activity at three extraction methods In vitro. The cold-water extract of Cassia sp., Cinnamomum sp., and Catharanthus sp. exhibited good anti-fungal activity against all two tested fungi. In the case of the hot water extracts, Catharanthus sp., and Lantana sp. showed the best anti-fungal activity against all two tested fungi. Ethanol extracts of Cassia sp., Ricinus sp., and Catharanthus sp. showed more than 10% inhibition against ISO 1. Of the three extraction methods, cold water extraction was generally more effective than other extraction methods. Cold water extract of Cinnamomum sp. inhibited the growth of ISO 1 and ISO 2 respectively 87.78% and 86.34%. Against two isolates cold water, hot water and ethanol extracts of Catharanthus sp. was effective in imposing more than 10% inhibition. Recommended dosage (1.8 gL-1 ) of the fungicide Homai (Thiophanate-methyl 50%+Thiram 30% WP) completely inhibited the mycelial growth of two isolates in vitro. Virulence of the Colletotrichum sp. varied significantly in terms of rapidity and extent of disease spread.

Keywords: Anti-fungal effects, Pathogenic variations, Anthracnose, Postharvest disease