Essential oil of peppermint in symbiotic relationship with Piriformospora indica and methyl jasmonate application under saline condition

Peppermint (Mentha piperita L.) is one of the most important medicinal and aromatic plants that its essential oil is extensively used in fragrance, aromatherapy, flavor, and pharmaceutical properties. This study aimed to evaluate the effects of Piriformospora indica inoculation, methyl jasmonate and salinity effects on essential oil from leaves, total phenol, anthocyanin, reactive oxygen species (ROS)-scavenger activity and composition of the oil in peppermint. Treatments included inoculation, and non-inoculation of P. indica, methyl jasmonate (0 and 75 mu M) and four salinity levels of irrigation water (0, 3, 6 and 9 dS m(-1)). Essential oil constituents have been analyzed by GC-MS. The results showed that salinity increased lipid peroxidation as well as membrane electrolyte leakage, while, membrane permeability influenced by methyl jasmonate application, P. indica inoculation and their interaction, reduced the negative effect of salinity on membrane electrolyte leakage. Fungal symbiosis and methyl jasmonate application ameliorated the negative effects of salinity on essential oil content. The results showed that monoterpenes constitute the major components of essential oil. The main oil constituents, menthol, menthone and 1,8-cineole increased considerably in P. indica and methyl jasmonate treatments. The highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and polyphenol oxidase was observed in the P. indica inoculation, however methyl jasmonate treatment gave the highest content of total phenol and anthocyanin. In general, when inoculated plants were sprayed by methyl jasmonate, antioxidant activity increased and synthesis of medicinal and anti-microbial compounds was observed.