EFEITO DO EXTRATO FOLIAR DE Gossypium arboreum L. (ALGODÃO) SOB O CRESCIMENTO MICELIAL DE Lasiodiplodia theobromae (PAT.) GRIFFON & MAUBL

Abstract

The use of plant extracts have been widely studied as an alternative biological control of plant diseases, especially those caused by phytopathogenic fungi. The aim of this study was to evaluate in vitro the antifungal activity of crude ethanolic extract obtained from tree cotton leaves ( Gossypium arboreum L., Malvaceae) in different concentrations on mycelial development of the pathogenic fungi Lasiodiplodia theobromae . The experiment was conducted in the Microbiology/Plant pathology/Genetics and Cultivation/Isolation laboratories, the State University of Amapa/UEAP, in Macapa, Amapa. In a Completely Randomized Design (CRD), six treatments and six repetitions were organized: T1 (negative control) - PDA (Potato-Dextrose-Agar) + 0 mg.mL -1 (leaf extract); T2 - PDA + 5 mg.mL -1 (leaf extract); T3 - PDA + 10 mg.mL -1 (leaf extract); T4 - PDA + 20 mg.mL -1 (leaf extract); T5 - PDA + 2.5 mL of ethanol and T6 (positive control) - PDA + 2.5 ml of a commercial fungicide (Derosal®). The variables mycelial growth inhibition (MGI), mycelial growth velocity index (MGVI) and area under mycelial growth curve (AUMGC) were calculated at the end of the experiment. The results showed the crude ethanolic extract of leaves of G. arboreum not presented antifungal activity in vitro against the fungus L. theobromae at the concentrations tested. The extract induced the mycelial growth, especially in a concentration of 10 mg.mL -1 , which exhibited ideal condition for the development of fungal structures. Keywords: Malvaceae; plant extract; biological control; phytopathogen.