Dynamic changes in cell wall-degrading enzymes and physio-biochemistry of ginseng in response to fusarium oxysporum infection

Ginseng root rot, caused by Fusarium oxysporum, is a serious disease in the ginseng industry in northeast China. This study aims to investigate the changes in ginseng physio-biochemistry following infection by Fusarium oxysporum, particularly the activities of cell wall degradation enzymes, antioxidant enzymes, and secondary metabolism-related enzymes. To do so, ginseng was artificially infected with a Fusarium oxysporum spore suspension, and changes in the activity of cell wall degrading enzymes (CWDEs), plant defense enzyme activity, malondialdehyde (MDA) and soluble sugar content were measured. The results showed that the activities of the cell wall degrading enzymes in the infected ginseng were all, to different degrees, higher than those in the control group. In the infection group, the activities of carboxymethyl cellulase (Cx) and beta -glucosidase (beta G) reached a peak at 7 days after infection, the activities of polymethylgalacturonase (PMG) and polygalacturonase (PG) reached a peak at 14 days, and the activities of pectin methyl trans erasing (PGTE) and polygalacturonase (PMTE) reached peaked at 28 days. These results indicate that when ginseng was infected with Fusarium oxysporum, Cx and beta G were the main cellulase, PG and PMG were the main pectinase, and the peak activity of the cellulases was earlier than that of pectinases. After infection with Fusarium oxysporum, the physiological and biochemical indices in ginseng were closely related to its disease resistance response. The activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and lipoxygenase (LOX) in the infection group reached a peak on a certain day. The results showed that the activities of SOD, CAT, POD, PAL, PPO and LOX were all activated when ginseng was infected by Fusarium oxysporum. The malondialdehyde (MDA) content in the infection group reached a peak at 7 days and was lower than that in the control group, indicating that the cell membrane damage of ginseng reached a maximum 7 days after inoculation. The soluble sugar content in the infection group was always higher than that in the control group. This result may be due to the enhanced respiration of the body, which promotes the degradation of starch and cellulose into soluble sugar, and is a self-protective reaction. In a word, ginseng has a defense effect after being infected by Fusarium oxysporum, and changes in CWDEs, plant defense enzymes activity, malondialdehyde and soluble sugar content in vivo to resist pathogenic invasion. The study provides a scientific basis for further exploring the mechanisms underlying the interaction between ginseng and root rot bacteria.