Control effects of metabolites of endophytic fungus Alternaria sp. GHX-P17 on bacterial wilt and changes of protective enzymes in Pogostemon cablin

Abstract

There is a long history to cultivate the Pogostemon cablin in Guangdong Province, and it is a famous medicinal material. The bacterial wilt is the important disease that impacts the production and quality of P. cablin. Aiming to the control effects of metabolites of Alternaria sp. GHX-P17 strain that is belonging to an endophytic fungus isolated from the stems and leaves of P. cablin and the mechanism of disease resistance on bacterial wilt, a laboratory experiment had been conducted to investigate the incidence and severity of bacterial wilt in P. cablin at different time after artificial to inoculate the strain of Alternaria sp. GHX-P17 and to spray the crude extracts of the metabolites, and disease index (DI) was calculated. The activity changes of protective enzymes of phenylalanine ammonia lyase (PAL), peroxidase (POD）and superoxide dismutase (SOD) were determined in different time in P. cablin. The results were as follows: (1) The DI was significantly lower in the treatment groups with the crude extracts of Alternaria sp. GHX-P17 at different concentrations than that of control groups, and the DI decreased by 27.16% in the treatment groups at 204 h after inoculation. The variance analysis showed significant differences (P<0.05). (2) The severity of bacterial wilt was reduced with the extension of investigation time in P. cablin, and the severity levels increased slowly in treatment groups. The average severity was significantly lower than that of the control groups at 204 h, and the control effects reached 74.65%. (3) The activities of protective enzymes of PAL, POD and SOD increased observably after to inoculate spore suspension and to spray metabolites in P. cablin, but the activity peak time was different. PAL activities gradually increased after inoculation; POD first increased and then decreased, and then increased again, and there were two the activity peaks; SOD increased rapidly and then decreased gradually. Obviously, the metabolites of Alternaria sp. GHX-P17 can not only increase the activities of protective enzymes in P. cablin, and delay the infection process of Ralstonia solanacearum, but also decrease the severity levels of bacterial wilt. However, the research findings provide a reference for the study of active components of secondary metabolites of endophytic fungi and the development of biopesticides.

Keywords

• endophytic fungi
• metabolites
• control effects
• bacterial wilt
• pogostemon cablin
• protective enzymes