Abstract
Chemical agents in the rhizosphere soils of plants might have an influence on root-rot disease, which therefore might reveal the mechanism of root rot in Panax notoginseng (P. notoginseng). With this hypothesis the alterations of phenolic acids (PAs) in the rhizosphere soils of P. notoginseng after pathogen infection were determined. The effects of PAs on the growth of Fusarium oxysporum (F. oxysporum), a fungal pathogenic factor for P. notoginseng, as well as production of fusaric acid, a wilting agent for the plants, were also examined. The results indicate the presence of five PAs (ferulic acid, syringic acid, p-hydroxybenzoic acid, p-coumaric acid, and vanillic acid) in the rhizosphere soils of P. notoginseng, whose contents in the rhizosphere soils of healthy plants are higher than those of the diseased ones. Further we found that individual PA could inhibit the mycelium growth and spore production of F. oxysporum, but stimulate fusaric acid production as well, disclosing the double-edge sword role of PAs in the occurrence of root rot of P. notoginseng and paving the way for the intervention of P. notoginseng root rot via balancing PAs.
Highlights
The root of Panax notoginseng (Araliaceae), known as San-Qi in Chinese, is a common and prominent traditional Chinese medicine due to its hemostatic and restorative properties
Five Pas, including p-hydroxybenzoic acid, vanillic acid, syringic acid, p-coumaric acid, and ferulic acid were detected in the rhizosphere soils of P. notoginseng
Levels of all these phenolic acids (PAs) were much higher in rhizosphere soils of healthy plants than those of diseased ones (P < 0.05) with p-coumaric acid being the highest (14.7502 μg/g), exceeding by 2.79-fold that found in rhizosphere soils of diseased roots. p-Hydroxybenzoic acid was the second highest, with a concentration of 5.5405 μg/g in the rhizosphere soils of healthy roots but 3.2969 μg/g in the diseased ones
Summary
The root of Panax notoginseng (Araliaceae), known as San-Qi in Chinese, is a common and prominent traditional Chinese medicine due to its hemostatic and restorative properties. P. notoginseng is mainly spread over southwestern China, with Wenshan County of Yunnan Province being known as the main producing area [1]. The remarkable curative effects of San-Qi on cardiovascular diseases has resulted in a great demand far exceeding wild supply. Cultivation of San-Qi meets the demand, one problem arising from scaled-up cultivation is root rot, which is a bottleneck limiting further development of the San-Qi industry. Root-rot disease could be caused by bacteria and nematodes, but it mainly results from fungal pathogens such as Fusarium and Cylindrocarpon species [2].
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