Bioatividade de extratos e óleo essencial de Cymbopogon citratus (DC.) Stapf frente ao fitopatógeno Colletotrichum gloeosporioides.

Abstract

The use of synthetic pesticides to control pests in plants causes damage to the environment and human health. Opposed to this reality, the use of natural products, such as plant extracts, has emerged as a viable alternative in the control of phytopathogens. Thus, this study aimed to evaluate the bioactive action of essential oil and crude extracts of holy grass (Cymbopogon citratus (DC.) Stapf) on the mycelial development of the C. gloeosporioides phytopathogen. For the study, the content of chlorophylls, carotenoids, flavonoids, anthocyanins and total phenolic compounds in the crude extracts was determined. For in vitro analysis, the PDA culture medium incorporated in the oil and extracts, in four defined concentrations, was poured into Petri dishes with five replicates for each treatment. Micro disks of C. gloeosporioides were inoculated in the center of the dishes and incubated in a BOD incubator at 25 ºC ± 2 ºC. Colony growth measurements were taken daily for seven days and the results were determined by calculating the Percentage Inhibition (PI) of mycelial growth and the Mycelial Growth Speed Index (MGSI). It was observed that the best results were obtained by the essential oil in the concentration of 0.25% (250 μL.100 ml- of the medium) and by the aqueous extract in the concentration of 1%, since they presented the highest averages of PI (100% and 87%) and the greatest reductions in the MGSI (0 and 0.11 cm day-1), respectively, followed by alcoholic extract with a maximum PI of 23.5% and MGSI minimum of 0.68 cm day-1, at a concentration of 1.5%. Thus, the results indicate the presence of biologically active compounds in the products derived from C. citratus analyzed with effective action on the mycelial growth of the phytopathogen C. gloeosporioides.