In vitro assessment of the efficacy of three essential oils of aromatic plants against Magnaporthe oryzae B.C. Couch, a rice blast pathogen in Burkina Faso

Abstract

Blast, caused by Magnaporthe oryzae B.C.Couch, is the main fungal disease in the rice fields in Burkina Faso. Three pure essential oils at different concentrations of Cymbopogon schoenanthus, Ocimum americanum and Lippia multiflora, and four of their combinations were tested in vitro to evaluate their inhibition properties on mycelial growth, sporulation, and spore germination of M. oryzae. The contact method and the fumigation method were used for the different tests at doses of 0.05 μl/ml, 0.1 μl/ml, 0.3 μl/ml, 0.6 μl/ml, 0.9 μl/ml, 1.2 μl/ml, 1.5 μl/ml, 1.8 μl/ml, 2.1 μl/ml and 2.4 μl/ml. Two chemical fungicides, mancozeb and azoxystrobin and an absolute control were used in the trials. The results showed that the pure essential oil of L. multiflora and its combination with that of C. schoenanthus presented the most effective minimum doses of inhibition in the contact and fumigation method. These doses ranged from 0.1 μl/ml to 0.3 μl/ml for 100% inhibition of radial growth, sporulation, and spore germination of Magnaporthe oryzae. Mancozeb inhibited 100% of all parameters evaluated, while azoxystrobin was ineffective. The essential oil of L. multiflora and its combination with that of C. schoenanthus can be tested in a real environment to control rice blast.