Abstract
Plant roots host diverse microbes that are closely associated with root fitness. Currently, the relationship between microbes and rusty roots of Panax ginseng remains unclear. Here, we described the root-associated microbiome in rusty and healthy ginseng by metagenomic sequencing of 16S rRNA and ITS regions. Being enriched in Diseased-roots (Dr) of ginseng and their rhizosphere soil, the fungus of Ilyonectria, was identified as the most probable cause of the disease after ITS analysis. Meanwhile, an increase of Mortierella was observed in Healthy-roots (Hr). Surprisingly, an enriched Fusarium was found in both Hr and their rhizosphere soil. Besides, in comparison with Hr, decreased relative abundance of Actinomycetales and increased relative abundance of Pseudomonadales was observed in Dr after 16S rRNA analysis. What’s more, we isolated several microorganisms as antagonists that showed strong inhibiting effects on Ilyonectria in plate assays. In field trials, inoculation of Bacillus sp. S-11 displayed apparent suppression effect against Ilyonectria and shifted microbial communities in rhizosphere soil. Our research identified key microbiota involved in rusty roots of P. ginseng and offered potential biocontrol solutions to rusty disease.
Highlights
Terrestrial plants are colonized by diverse microorganisms which include commensals, symbionts, and opportunistic pathogens (Muller et al, 2016)
Principal coordinate analysis (PCoA) result demonstrated dramatic discrepancies in the structure of fungal community (Figure 2C, F = 2.227, p = 0.005) between groups of Hr and Dr After assignment, we found that the fungal microbiome showed severe dysbiosis in rusty roots
Our results revealed that the fungal microbiome showed severe imbalance in rusty tissues that mainly attribute to the abundance of Ilyonectria
Summary
Terrestrial plants are colonized by diverse microorganisms which include commensals, symbionts, and opportunistic pathogens (Muller et al, 2016). The colonized microbes present in endosphere and rhizosphere have a direct relationship with the fitness of plant roots. A previous study elucidated the microbes in disease-suppressive soils against pathogen in sugar beet (Mendes et al, 2011). They found several key bacterial taxa and genes involved in suppression of Rhizoctonia solani. A recent study revealed that Flavobacteriia was enriched in tomato rhizosphere, which was resistant to the soil-borne pathogen Ralstonia solanacearum. Metagenomics is a powerful tool for revealing the microbiota related to pathogentriggered root diseases, offering possible solutions to preventing pathogen-infection in plants
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