Abstract

The antifungal potential of five species of Trichoderma viz., Trichoderma viride,Trichoderma aureoviride, Trichoderma reesei, Trichoderma koningii and Trichoderma harzianum was investigated in vitro against Alternaria citri, the causal agent of the black rot disease on a broad range of citrus cultivars. Cultural filtrates of Trichodermaspecies were obtained by growing them on different media. The effect of different filtrate concentrations revealed that aqueous extracts of all Trichoderma species significantly reduced the fungal biomass of the target fungal pathogen. Generally, 100% culture filtrate of the test Trichoderma species significantly reduced the growth of fungus. On each medium, a different response was observed. Culture filtrate of T. harzianum was found highly effective in suppressing growth (up to 93%) of the test fungal species grown on malt extract medium. T. harzianum and malt extract medium were therefore selected for fraction analysis. There was 68% reduction in growth of the A. citri due to 1% concentration of ethyl acetate fraction of cultural filtrate of T. harzianum when grown in malt extract broth.

Key words: Citrus, Alternaria citri, ethyl acetate fraction, Trichoderma harzianum, viride, aureoviride, reesei, koningii.