Effects of Fusarium solani and F. oxysporum Infection on the Metabolism of Ginsenosides in American Ginseng Roots.

Xiaolin Jiao,Jianjun Hao,Xiaohong Lu,Yi Luo,Weiwei Gao,Amanda Chen

doi:10.3390/molecules200610535

Abstract

American ginseng (Panax quinquefolius L.) is a highly valuable herb widely used for medicinal treatments. Its pharmacologically important compounds are the ginsenosides, which are secondary metabolites in American ginseng root. The concentrations of ginsenoside in roots can be changed by fungal infection, but it is unclear what specific root tissues are impacted and whether the change is systemic. In this study, American ginseng roots were inoculated with two fungal pathogens (Fusarium solani or F. oxysporum) and the levels of six ginsenosides (Rb1, Rb2, Rc, Rd, Re, and Rg1) were then measured in the phloem and xylem around the discolored lesions and adjacent healthy areas of the root. Results indicated that the growth of Fusarium spp. was strictly limited to phloem, and correspondingly the ginsenoside concentration was only altered in this infected phloem. The concentration of Rg1, Rd, and Rc significantly changed in phloem tissues where F. solani was inoculated, while only Rg1 and Rd changed significantly after F. oxysporum inoculation. However, no changes of any ginsenoside occurred in either xylem or phloem tissue adjacent to the inoculation point. In addition, when two Fusarium spp. were grown on ginsenoside-amended Czapek medium, the majority of ginsenosides were depleted. Therefore, pathogenic Fusarium spp. may reduce ginsenoside levels by consuming them.

Highlights

American ginseng (Panax quinquefolius L.) is mainly cultivated in the United States, Canada, andChina [1]
Ginseng roots growing in the field are susceptible to several soil-borne diseases. These diseases are primarily caused by fungal pathogens, including several species of Fusarium [10,11,12], Rhexocercosporidium panacis [13], Cylindrocarpon destructans [14,15], Phytophthora cactorum [14,16], and Pythium species [15]
Compared to the amount initially added to the medium, Rg1, Re, Rb1, Rc, Rb2, but not Rd, were substantially depleted in the medium with F. solani or F. oxysporum (Figure 6). The degradation of these ginsenosides occurred after three to five days of co-culturing with the fungi (Figure 6). These results suggested that both F. solani and F. oxysporum were capable of inducing metabolic changes of major ginsenosides in American ginseng roots

Summary

Introduction

American ginseng (Panax quinquefolius L.) is mainly cultivated in the United States, Canada, andChina [1]. Ginseng roots growing in the field are susceptible to several soil-borne diseases These diseases are primarily caused by fungal pathogens, including several species of Fusarium [10,11,12], (causing root rot or rusty root), Rhexocercosporidium panacis (causing rusty root) [13], Cylindrocarpon destructans (causing root rot) [14,15], Phytophthora cactorum (causing Phytophthora root rot) [14,16], and Pythium species (causing damping-off) [15]. Among these pathogens, Fusarium solani and F. oxysporum are highly aggressive fungi causing American ginseng root rot in the Beijing ginseng producing region of

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