Effect of Crude Ethanolic Extracts From Bottle Brush (Callistemon Viminalis) Against Leaf Spot Fungi and Their Phytotoxicity on Lettuce (Lactuca Sativa L.)

In response to the public concern about environmental problems as well as fungicide residues on agricultural produces especially leaf vegetables, we investigated the potential use of crude extracts from bottle brush (C. viminalis) leaves against leaf spot fungi and their phytotoxicity on lettuce grown in hydroponics. Yield, total phenolic and flavonoid contents of the extract were also evaluated. Regarding the in vitro antifungal assay using poisoned food technique, 3×3 factorial in Completely Randomized Design (CRD) was employed with three replicates. Factor A was 3 crude extracts (50% ethanol, 70% ethanol and 95% ethanol crude extract) while factor B was the 3 concentrations (0, 5,000 and 50,000 ppm) of crude extracts. Results showed that all three crude extracts were significantly effective in inhibiting the mycelial growth and sporulation of leaf spot fungi (Alternaria sp. and Curvalaria sp.). There was a significant interaction between all extracts and their concentration regarding inhibition percent. Increase in crude extract concentrations resulted in a marked increase in their inhibition. The concentration of 50,000 ppm gave the highest effectiveness. For phytotoxicity test, all tested crude extracts did not give any negative effects either on seed germination or growth of lettuce grown in hydroponics. Interestingly, growth promotion about 30 percent was achieved on this regard. Based on quantitative assay, the highest yield of crude extract was obtained from 95% ethanol solvent. Highest total phenolic and flavonoid contents were detected at the highest concentration of all crude extracts.

Keywords: bottle brush extract; phytotoxicity; antifungal activity; leaf spot fungi; Alternaria; Curvularia

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