Isolating, Identifying, and Analyzing the Biological Characteristics of Pathogens Causing Postharvest Disease in Fresh Radix Astragali

Abstract

Radix Astragali (RA) is the root of Astragalus membranaceus var. mongholicus (Bunge) P.K. Hsiao. In order to determine targeted and effective methods for treating mold infections in fresh RA, pathogenic fungi were isolated and identified using morphology and molecular biology techniques, and factors affecting the growth of the pathogenic fungi, such as temperature, pH, light, and carbon and nitrogen sources, were analyzed. Changes in the main active ingredients of RA, such as carbohydrates, flavonoids, and saponins, were detected before and after infection with pathogenic fungi. The results showed that Penicillium polonicum, Trichothecium roseum, and Fusarium equiseti were the main pathogens causing postharvest disease in fresh RA. The optimum growth temperature for the three pathogens was 25 °C; P. polonicum was able to grow at an alkaline pH of 8–9, while T. roseum and F. equiseti grew better and had higher levels of sporulation under acidic conditions with pH values of 5–6. Different carbon and nitrogen sources had different effects on mycelium growth and sporulation. Darkness was favorable for the growth and sporulation of the three pathogens. Compared with healthy RA, the total carbohydrate, flavonoid, and saponin contents of the RA samples infected with the three fungi decreased. This study provides a theoretical basis for the scientific and precise control of RA postharvest disease during storage by targeting different pathogens and their growth conditions.