Transition from Ginseng Root Rot Disease-Conducive Soil to -Suppressive Soil Mediated by Pseudomonadaceae.

Ginseng is a popular medicinal herb with established therapeutic effects such as cardiovascular disease prevention, anticancer effects, and anti-inflammatory effects. However, the slow growth of ginseng due to soilborne pathogens has been a challenge for establishing new plantations. In this study, we investigated root rot disease associated with the microbiota in a ginseng monoculture model system. Our results showed that a collapse of the early microbiota community inhibiting root rot disease was observed before the disease became severe, and nitrogen fixation was necessary to support the initial microbiota community structure. Furthermore, changes in the nitrogen composition were essential for the suppression of pathogen activity in early monoculture soils. We hypothesize that Pseudomonadaceae, a population built up by aspartic acid, can inhibit the occurrence of root rot disease in ginseng and that specific management practices that maintain a healthy microbiome can be implemented to prevent and mitigate the disease. Our findings provide insights into the potential use of specific members of the microbiota for controlling root rot disease in ginseng cultivation. IMPORTANCE Understanding the initial soil microbiota and community shifts in a monoculture system is critical for developing disease-suppressive soils for crop production. The lack of resistance genes against soilborne pathogens in plants highlights the need for effective management strategies. Our investigation of root rot disease and initial microbiota community shifts in a ginseng monoculture model system provides valuable insight into the development of conducive soil into specific suppressive soil. With a thorough understanding of the microbiota in disease-conducive soil, we can work toward the development of disease-suppressive soil to prevent outbreaks and ensure sustainable crop production.

A mutualistic interaction between Streptomyces bacteria, strawberry plants and pollinating bees.

Microbes can establish mutualistic interactions with plants and insects. Here we track the movement of an endophytic strain of Streptomyces bacteria throughout a managed strawberry ecosystem. We show that a Streptomyces isolate found in the rhizosphere and on flowers protects both the plant and pollinating honeybees from pathogens (phytopathogenic fungus Botrytis cinerea and pathogenic bacteria, respectively). The pollinators can transfer the Streptomyces bacteria among flowers and plants, and Streptomyces can move into the plant vascular bundle from the flowers and from the rhizosphere. Our results present a tripartite mutualism between Streptomyces, plant and pollinator partners.

Variation in flavonoid levels in Citrus benikoji Hort. ex. Tan. infected by Colletotrichum gloeosporioides.

Anthracnose caused by Colletotrichum gloeosporioides is one of the most serious postharvest diseases of citrus fruit. Fruit peels infected with C. gloeosporioides and the peels of healthy fruit were analysed for flavonoids, using high performance liquid chromatography-tandem mass spectroscopy, to evaluate variations in flavonoid levels in Citrus benikoji Hort. ex. Tan. Seventeen flavonoids were characterised from the fruit peels. The flavonoids were validated using structurally related standards and quantified. Among the 17 flavonoids, the concentration of component 3 was the highest and that of component 10 was the lowest. During 8 days after inoculation, the concentration of the seven flavonoids 1-3, 5, 6, 13, and 14 increased gradually up to day 8. Flavonoid 4 was detected from day 7. The seven minor flavonoid components, 8-12, 15, and 16 increased to day 5 and then decreased. However, flavonoids level variations were not significantly different from that of the non-infected fruits during the experimental period. The monitoring suggested that the constitutively formed seven polymethoxyflavones (8-12, 15, and 16) may act as phytoanticipins in the defence mechanism against the fungus, and that hespertin 7-O-glucoside (4), produced de novo on day 6 after infection, may function as a phytoalexin.