Effects of Four Essential Oils of Aromatic Plants on Mycelial Radial Growth of Magnaporthe oryzae B.C.Couch., a Rice Blast Pathogen in Burkina Faso

Abstract

Rice blast, aused by Magnaporthe oryzae B.C.Couch, is considered as the main fungal disease in rice fields in Burkina Faso. This study aimed to assess the essential oils of Cymbopogon schoenanthus, Ocimum americanum, Ocimum gratissimum and Lippia multiflora on mycelial radial growth and inhibition rate of the fungus using the contact and fumigation methods. For each essential oil, six doses were used : T0 (0 µl/ml), T1 (0.1 µl/ml), T2 (0.6 µl/ml), T3 (1.2 µl/ml), T4 (1.8 µl/ml) and T5 (2.4 µl/ml). In both tests, two treatments of synthetic fungicides namely Tma (mancozeb) and Taz (azoxystrobin) at recommended doses of 6.67 µl/ml and 3.33 µl/ml respectively. The results showed that in the contact method, essential oils of L. multiflora, O. americanum,C. schoenanthus and O. gratissimum inhibited 100% (0 cm of diameter) the fungus mycelial radial growth at doses of T3 (1.2 µl/ml), T5 (2.4 µl/ml), T2 (0.6 µl/ml) and T2 (0.6 µl/ml) respectively. As for the fumigation method, oils of L. multiflora, O. americanum,C. schoenanthus and O. gratissimum inhibited mycelial radial growth of the fungus by 100% at doses of T2 (0.6 µl/ml), T5 (2.4 µl/ml), T4 (1.8 µl/ml) and T3 (1.2 µl/ml) respectively. Mancozeb and azoxystrobin treatments inhibited radial mycelial growth by 100% and 74.1% respectively. These essential oils can be used to control rice blast in the field. The use of these essential oils in rice blast management may also help to reduce environmental pollution caused by synthetic fungicides.”