Publicação on-line; 15 ref.; 3 illus.; Summaries (En, Pt)

RESUMO:

Além do valor como recurso terapêutico, plantas medicinais também possuem
potencial para serem utilizadas como fonte de princípios ativos contra fitopatógenos. O objetivo
deste trabalho foi avaliar o efeito de óleos essenciais das espécies medicinais Baccharis
dracunculifolia (alecrim-do-campo), Schinus terebinthifolius (aroeirinha) e Porophyllum ruderale
(arnica-brasileira) sobre o crescimento dos fungos fitopatogênicos Fusarium oxysporum f. sp.
phaseoli (Fop), F. solani f. sp. phaseoli (Fsp), Sclerotinia sclerotiorum (Ss), S. minor (Sm),
Rhizoctonia solani (Rs), Sclerotium rolfsii (Sr) e Macrophomina phaseolina (Mp). Avaliou-se em
placas de Petri o crescimento radial desses fungos em meio batata-dextrose-ágar (BDA) com
cinco concentrações (0, 250, 500, 1000 e 3000 mg L-1) dos óleos essenciais. Discos de micélio
(5 mm de diâmetro) de cada fungo em crescimento foram transferidos para placas de Petri que
foram mantidas a 23°C no escuro por 48 horas. O óleo essencial de alecrim-do-campo foi o
mais eficiente na redução do crescimento micelial de todos os fungos, com inibição completa
quando se utilizou a concentração de 3000 mg L-1. A redução de crescimento variou de 29%
(Fs) a 80% (Rs) a 250 mg L-1 do óleo essencial de alecrim-do-campo; a 500 mg L-1, variou de
29% (Fs) a 98% (Sr); e a 1000 mg L-1, de 41% (Fs) a 100% (Sr). A redução do crescimento
dos fungos pelo óleo de aroeirinha na concentração de 3000 mg L-1 variou de 27% (Fsp) a
74% (Rs). Nessa concentração, o óleo de arnica-brasileira reduziu o crecimento micelial de Ss
em 72%, o de Rs em 80% e o de Mp em 82%, sem efeitos significativos sobre o crescimento
micelial de Fsp e Fop. Conclui-se que os óleos essenciais de alecrim-do-campo, aroeirinha
e arnica-brasileira possuem potencial para o controle dos fungos fitopatogênicos estudados,
com destaque para o óleo de alecrim-do-campo.

Palavras-chave: controle alternativo, alecrim-do-campo, aroeirinha, arnica-brasileira.

ABSTRACT:

Potential of essential oils from medicinal plants to control plant pathogens.
In addition to their value as therapeutic resources, medicinal plants also have the potential
to be used as a source of alternative compounds against plant pathogens. The objective of
this study was to evaluate the effect of essential oils extracted from the medicinal species
Baccharis dracunculifolia, Schinus terebinthifolius and Porophyllum ruderale on the growth of
the fungal plant pathogens Fusarium oxysporum f. sp. phaseoli (Fop), F. solani f. sp. phaseoli
(Fsp), Sclerotinia sclerotiorum (Ss), S. minor (Sm), Rhizoctonia solani (Rs), Sclerotium rolfsii
(Sr) and Macrophomina phaseolina (Mp). The radial mycelial growth of the fungi was evaluated
on potato dextrose agar (PDA) in Petri dishes with five concentrations (0, 250, 500, 1000 and
3000 µL L-1) of the essential oils. Mycelial discs (5 mm diameter) of the growing colonies of
each fungus were transferred to Petri dishes, which were maintained at 23 °C in the dark for
48 hours. The essential oil of B. dracunculifolia was the most effective oil in the reduction of the
mycelial growth of all fungi. It completely inhibited their growth at 3000 mg L-1. At 250 mg L-1, the
growth reduction caused by the oil of B. dracunculifolia varied from 29% (Fs) to 80% (Rs); at
500 mg L-1, it varied from 29% (Fs) to 98% (Sr); and at 1000 mg L-1, it varied from 41% (Fs) to
100% (Sr). The reduction of the mycelial growth caused by the oil of S. terebinthifolius at 3000
mg L-1 varied from 27% (Fsp) to 74% (Rs). At this concentration, the oil of P. ruderale reduced
the mycelial growth of Ss by 72%, of Rs by 80% and of Mp by 82%, without significant effects
on the mycelial growth of Fsp and Fop. We conclude that the essential oils of B. dracunculifolia,
S. terebinthifolius and P. ruderale have the potential to be used to control the plant pathogens
tested, especially the oil of B. dracunculifolia.

Kew words: alternative control, Baccharis dracunculifolia, Schinus terebinthifolius, Porophyllum
ruderale.