[Influence of continuous cropping on growth of Artemisia annua and bacterial communities in soil].

In this study, several types of Artemisia annua in soil, including the soil which had not been planted, or planted for one year, or continuously planted for three or five years were collected, in order to study the influences of continuous cropping on the growth of A. annua, content of artemisinin, available nutrient of soil, and bacterial community structure through adopting routine analysis and Illumina MiSeq high-throughput sequencing. The results showed that continuous cropping inhibited significantly the growth of A. annua and reduced leaf biomass, content and yield of artemisinin, with the maximum decreasing amplitude of 30.20%, 7.70% and 35.58% respectively. The content of soil organic matter, available nitrogen, available phosphorus and 16S rRNA sequence number were increased to different extents after continuous cropping of A. annua. According to the results of high-throughput sequencing, 634-812 types of common bacteria belonged to 21 categories were planted in different soil of A. annua with different planting years, which represented that the distribution distance of the point of bacterial community with different years among coordinate system of principal component was relative distant, and community structure had significant changes (P<0.05). As the planting years increased, the abundance of Actinobacteria, Chloroflexi, Gemmatimonadetes decreased in contrast to Proteobacteria, Acidobacteria and Verrucomicrobia. In the top 20 types of predominant bacteria,Nitrospira japonica and Nitrospira disappeared, among which, only Gemmatimonadaceae, Micromonosporaceae, Nitrosomonadaceae, Xanthobacteraceae, and unculture bacterium JG30-KF-AS9 were similar, indicating that the planting and continuous cropping of A. annua selectively inhibited the growth and reproduction of soil bacteria, and influenced the supply and transform of soil nutrient, leading to a poor growth and resulting in reduction of artemisinin content and yield. Therefore, it is necessary to advocate crop rotation in the process of planting A. annua.
Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose.
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