Alternative control of early blight of tomato using plant extracts from Acacia nilotica, Achillea fragrantissima and Calotropis procera

Abstract

The in vitro and in vivo antifungal potential of extracts of three wild medicinal plants, (Acacia nilotica (L.) Delile, Achillea fragrantissima (Forssk.) Sch.Bip. and Calotropis procera (Aiton) W. T. Aiton) was examined against Alternaria solani, the causal agent of the early blight of tomato. Aqueous or ethanol extracts of all tested plants reduced the mycelial growth and conidium germination of A. solani in vitro. Ethanol extracts were more effective against the pathogen than the aqueous extracts. Extract of C. procera exhibited more antifungal potential against the pathogen than other plant extracts. Observations by scanning and transmission electron microscopy showed dramatic alterations in the morphology and ultrastructure of A. solani when treated with the ethanol extract of C. procera at a concentration of 20%. Phytochemical screening confirmed the presence of many bioactive constituents in the extracts which were in greater amounts in C. procera than the other two plants. In a plot experiment, both types of extracts from C. procera reduced disease severity. Tomato fruit yield was increased after the treatment with the plant extracts.