Foliar application of liquiritin protects Chinese flowering cabbage against cucumber mosaic virus and increases health-promoting compounds

Abstract

Decades of research have revealed notable similarities between the immune systems of the plant and animal kingdoms. Liquiritin has long been used to stimulate the body immunity in animals against an array of diseases. Considering the homology of some induced immune responses between animals and plants, we examined the effects of exogenously applied liquiritin to stimulate defense responses in Chinese flowering cabbage plants against cucumber mosaic virus (CMV) infection under greenhouse and field conditions. Foliar application of liquiritin (200 ppm) effectively suppressed the development of CMV symptoms by not less than 40% compared with the control in cabbage plants in both greenhouse and field trials along with the significant increases in the marketable yield and nutritional quality of cabbage. Liquiritin application enhanced the production of phenolic compounds and different defense-related enzymes in treated plants. Moreover, quantitative real-time PCR analysis revealed that liquiritin significantly up-regulated the expression of different defense-related genes upon pathogen inoculation, indicating an induction of the salicylic acid-mediated defense system. Collectively, the findings of this study indicate that liquiritin can effectively control CMV in cabbage plants.