In vitro activity of plant extracts against some important plant pathogenic fungi of tomato

Abstract

ndiscriminate use of synthetic pesticides has resulted in loss of access to niche markets due to presence of chemical residues in fresh vegetable produce. There is need for safe alternatives to synthetic pesticides in management of pests and diseases in horticultural production. The objective of this study was to evaluate effectiveness of plant extracts in suppressing growth of plant pathogenic fungi in vitro. Mature plant tissue samples were finely blended, extracted with 95% (v/v) ethanol and the extracts were concentrated by evaporation under vacuum at 600C to remove the ethanol. Antifungal activity of the extracts was tested by incorporating the extract into the culture media onto which fungal pathogens were then cultured. Sensitivity of the fungal pathogens was determined by measuring the pathogen colony radial growth of the treatments compared to controls. Extracts from different plants varied in activity, with turmeric extracts being the most active. Turmeric extracts inhibited fungal colony radial growth by 30 to 73 % while mint was the least active. Alternaria solani was the most susceptible pathogen while Pythium ultimum was the most sensitive to extracts from all the plants evaluated. Fusarium oxysporum f. sp. lycopersici was tolerant to most of the plant extracts tested. Sensitivity of all the pathogens tested was found to decrease with the age of the cultures. The study showed that plants extracts contain compounds that inhibit growth of plant pathogenic fungi. Such compounds could be exploited as biopesticides to manage plant diseases thereby reducing the chemical residues in horticultural production.