Comprehensive transcriptomics and metabolomics revealed the antifungal mechanism of Cymbopogon citratus essential oil nanoemulsion against Fusarium solani

Abstract Background Fusarium solani ( F. solani ) is the main pathogen causing root rot of Panax notoginseng (Burk.) F. H. Chen ( P. notoginseng ). Cymbopogon citratus (DC.) Stapf ( C. citratus ) essential oil (EO) is a mixture of various active ingredients with good antifungal effects and no residue. However, due to its hydrophobicity and oxidation, its bioavailability is low. Results In this study, EO was made into a nanoemulsion using Tween-80 and anhydrous ethanol by ultrasonication. The antifungal activity of the traditional emulsion (TEO) and C. citratus nanoemulsion (NEO) was compared by measuring the effects on spores and mycelia and in vivo assays. The components of EO, TEO, and NEO were analyzed by GC‒MS, and the inhibitory mechanism of the emulsion against fungi was revealed by combining transcriptomics and metabolomics. The prepared NEO was a clear and transparent homogeneous liquid with a particle size of 15.86 ± 1.96 nm. It was an oil-in-water nanoemulsion and maintained good stability in different environments. The contents of antifungal components such as citronellal and linalool in NEO were significantly higher than those in TEO. The antifungal effect of NEO against F. solani was increased by 8 times compared with that of TEO. Through transcriptomic and metabolomic analyses, it was found that both NEO and TEO inhibited the fungi by destroying the cell membrane, thereby affecting the ribosome, meiosis and TCA cycle of the fungi, and NEO had a deeper effect than TEO. NEO also inhibited the gene expression of the CYR1 enzyme and decreased the amount of d -trehalose, thus inhibiting the germination of spores and thereby affecting the growth of mycelia. Conclusions This study not only solved the problem of EO insoluble in water and low bioavailability but also greatly improved the antifungal activity, revealing the antifungal mechanism and the reason for the enhancement of NEO activity. It provides theoretical research for further development and utilization of EO to produce environmentally friendly pesticides or fertilizers and alleviate root rot of medicinal plants. Graphical Abstract