Changes in the soil microbial community are associated with the occurrence of Panax quinquefolius L. root rot diseases

Abstract

Root-rot disease, a catastrophic disease of Panax quinquefolium L. causes yield reduction and serious economic losses. However, knowledge of the relationship between rhizosphere microbial community and root-rot disease is limited. This study is aim to test whether the bacteria and fungi community differed between the soil attached to healthy and rotten roots of American ginseng. Moreover, the effects of American ginseng cultivation for 4 years on changes of soil physiochemical properties and microbial community were also investigated. High-throughput sequencing (Illumina MiSeq) was used to investigate the difference of microbial communities in the soils of new farmland (C) and the rhizosphere soils around healthy (H) and root rot diseased ginseng (R). Cultivation of American ginseng for 4 years not only changed the soil physicochemical properties, but also significantly increased the richness of the soil bacteria and decreased the fungal richness and diversity. Compared with other genera, the bacterial genera Nitrospira and the fungal genera Gibberella and Podospora were strongly enriched in the soil of new farmland. However, the relative abundance of Janthinobacterium, Nitrospira and Pedomicrobium in bacterial community, and Mrakia, Paradendryphiella, Sporopachydermia, Myrothecium and Racocetra in fungal community were significantly decreased after culture of American ginseng. The results also showed that the bacteria and fungi community differs between the soil attached to healthy and rotten roots of American ginseng. The richness indices of fungal community showed a significant decrease in rhizosphere soils of R comparing with H. The bacteria Rhodoplanes and Kaistobacter were the dominant genera in the H sample, whereas Sphingobium was dominant in the R sample. Notably, Monographella was significantly higher in the R sample (23.13%) than that of H sample (2.90%). In addition, the fungi Melanophyllum and Staphylotrichum were the most differently abundant in the H sample, whereas Mortierella and Cistella were the differently abundant genera in the R sample. Our results indicate that cultivation of American ginseng changed the edaphic factors and the soil microbial community, and there are significant differences in the microbial community between the soil attached to healthy and rotten roots of American ginseng.