Effect of antifungal activity of neem essential oil and its constituents on growth performance and its enzyme effectiveness on pathogenicity to Fusarium spp

Background and Objectives:

 The genus Fusarium has a worldwide distribution and many of its species, especially Fusarium graminearum Schwabe and Fusarium culmorum (W.G. Smith) Saccardo can infect a wide range of host plants and cause a variety of economically important diseases. The aim of this study was to identify the constituents of essential oil from leaves of native neem tree (Azadirachta indica A.Juss.) and their effect on growth performance and activity of cell wall degrading enzymes produced by these pathogens. 

Materials and Methods:

 The leaves of neem tree were obtained from Iranshahr region of Sistan and Baluchestan province and dried in the shade. The essential oil was extracted by hydrodistillation using a clevenger apparatus and its major constituents were identified by gas chromatographymass spectrometry. 

Results:

 The major constituents in the essential oil were β-elemene (27.2%), caryophyllene (15.9%) and phytol (15.3%), which have antifungal effects against F. graminearum and F. culmorum. The results showed that although the pathogenicity of F. culmorum was lower than F. graminearum, but the minimum inhibitory concentration of essential oil, βelemene, caryophyllene and phytol against F. graminearum was higher than F. culmorum. Sporulation and spores germination of Fusarium spp. were completely inhibited by essential oil and phytol. Synergistic effects of the main constituents of essential oil showed that combining phytol with caryophyllene induced a synergistic activity against Fusarium spp. and in combination with β-elemene caused an additive effect. Activities of cellulase and pectinase, as main cell wall degrading enzymes were decreased by essential oil and its main constituents at low concentration without affecting mycelial growth of fungi studied. 

Discussion:

 The findings of this research showed that there is a possibility of using neem oil and phytol compound to control diseases caused by Fusarium species.