Abstract
In-vitro study of Chromolaena odorata extracts was determined against isolated Phytophthora megakarya for the purpose of investigating the antifungal activity of ethanolic, cold-water and warm-water extracts of the medicinal plant against Phytophthora megakarya. Their antifungal effects were assessed with agar-well diffusion methods. Phytochemical screening and minimum inhibitory concentrations of the extracts were also determined. A qualitative phytochemical analysis of the extracts showed the presence of biologically active constituents such as flavonoids, phenols, tannins, sterols, amino acid and glycosinulate. Results showed that antifungal effects of Chromolaena odorata against Phytophthora megakarya were most efficient by ethanolic extracts, followed by extract of cold-water while hot water extract had no visible antifungal effect. Zones of clearance range from 15.00 mm to 32.00 mm using ethanolic extractions with concentrations from 1% to 5% while zones of clearance using cold water extract was from 5.00 mm to 30.00 mm with varying concentrations of 1% to 5%. The negative control using sterile distilled water showed no inhibitory effect on Phytophthora megakarya while 41.00 mm zone of clearance was observed in the positive control test using Metalaxyl and cuprous oxide-containing synthetic fungicide. This study provides a scientific confirmation of the use of Chromolaena odorata against cocoa pod infections by some local farmers.Asian J. Med. Biol. Res. March 2018, 4(1): 7-13
Highlights
Phytophthora spp. is a cosmopolitan genus of Oomycete obligate plant pathogens containing approximately 60 described species (Erwin and Ribeiro, 1996)
The results of the antifungal assay of the plant extract indicated that this plant exhibits antifungal activity against Phytophthora megakarya at different time interval
The result obtained in antifungal testing of the plant extract shows that the effectiveness of the plant extract varies with time and concentration of extracts
Summary
Phytophthora spp. is a cosmopolitan genus of Oomycete obligate plant pathogens containing approximately 60 described species (Erwin and Ribeiro, 1996). Phytophthora diseases are very common throughout the wet tropical regions of the world and cause significant diseases losses in many tropical fruit crops in the form of root rots, collar rots, stem cankers, leaf blights and fruit rot. P. palmivora alone causes a myriad of severe diseases on many different crops including: black pod of cocoa; root, stem and fruit rot of pawpaw; root rot and blight of citrus; bud rot in palms; black stripe in rot in durian. Phytophthora megakarya appears to be confined to West Africa (Zentmeyer, 1987), where it is the most common species of Phytophthora causing black pod disease of cocoa. The centre of origin is considered to be the basin of the Upper Amazon (Wood, 1975) This would indicate that if P. megakarya is only present in West Africa, it must have another host that is as yet undetermined and cocoa is a new host. No records appear to exist for P. megakarya outside West Africa and the only
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