Preventive effects of arbuscular mycorrhizal fungi and dark septate endophytes on ginger and the anti-disease mechanism

Abstract:

[Background] Ginger wilt caused by Ralstonia solanacearum (R.S) is a bottleneck in the development of the ginger industry. Arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) are two kinds of important symbiotic microorganisms. [Objective] To explore the mechanism of AMF and DSE against ginger wilt. The previous study found that AMF and DSE could improve the resistance of ginger wilt, however, the synergic functioning mechanism was unclear, which limited the application of the two kinds of fungi to control the disease. [Methods] The pot experiments were carried out at room temperature with ginger-cultured seedlings as the material. The control (CK) treatment inoculated with AMF and DSE and without AMF and DSE were set up. After 4 weeks of growth under the above treatment, the plants were eluted with pathogen solution. One week after pathogen inoculation, the effects of AMF and DSE on the ginger growth and physiological and biochemical indexes infected with the pathogen were studied by determining the mycorrhizal infection rate, incidence, chlorophyll content, photosynthetic index, phosphorus (P) content, defensive enzyme activity, and malondialdehyde (MDA) content. [Results] AMF and DSE reduced the incidence of ginger wilt in ginger by 45.27% and 52.04%, respectively (P<0.05). AMF+DSE had a better effect on the prevention and control of this disease, and the incidence was reduced by 60.87% as compared with the control (P<0.05). The preventive effects of AMF, DSE, and AMF+DSE were 62.54%, 59.02%, and 68.50%, respectively. The activity of plant defensive enzymes indicated that AMF significantly increased the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and polyphenol oxidase (PPO) by 10.87%, 1.15%, 13.26%, and 0.14%, respectively. DSE significantly increased the activities of SOD, POD, CAT, and PPO by 9.85%, 17.47%, 3.64%, and 0.67%, respectively. AMF+DSE significantly increased the activities of SOD, POD, CAT, and PPO by 15.76%, 18.19%, 18.11%, and 14.93%, respectively (P<0.05). AMF, DSE, and AMF+DSE significantly decreased the content of MDA by 3.38%, 9.31%, and 25.79%, respectively (P<0.05). [Conclusion] AMF and DSE have preventive effects on ginger wilt, which improve the disease resistance of ginger seedlings and promotes their growth, and the combination of AMF and DSE manifests the optimal effect.