The Innovation Team of Soil Health Care of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS), the CAAS-CIAT Sustainable Agriculture Joint Laboratory and the flower germplasm resources and genetic innovation team of the Institute of Vegetables and Flowers, CAAS explored the microbiological mechanism that causes continuous cropping obstacles of various cut chrysanthemum varieties under long-term monoculture.

The results were published in Frontiers in Microbiology.

According to associate professors Ruan Zhiyong and Zhao Xin, the output of cut chrysanthemum ranks among the top four cut flowers in the world, and it is widely planted in China. In order to obtain maximum economic benefits, commercial growers have adopted a single continuous cultivation method for a long time, resulting in the occurrence of continuous cropping obstacles, which has become an important factor affecting the quality of cut chrysanthemum and reducing their economic value.

In order to find out the reasons and microbial mechanism of continuous cropping obstacles in cut chrysanthemum soil, the team selected four cut chrysanthemum varieties and used amplicon sequencing technology to monitor the dynamic changes of rhizosphere soil microbial community under different continuous cropping years.

The results showed that continuous single cropping significantly changed the community structure of bacteria and fungi in the rhizosphere soil of the four types of cut chrysanthemum, significantly increased the richness of the fungal community, and transformed the microbial community of the rhizosphere soil of cut chrysanthemum to a "fungal type" community. With the increase of continuous cropping time, the biocontrol bacteria taxa in the rhizosphere soil gradually decreased, while the abundance of plant pathogens gradually increased.

Functional annotation of bacterial and fungal communities revealed that functional abundances related to nitrogen, sulfur metabolism, and chitin decomposition were significantly reduced in the rhizosphere soil of cut chrysanthemum, whereas plant pathogenic fungi with different trophic modes (from Acremonium, Plectosphaerellaceae, Fusarium, and Cladosporium) were significantly increased. it has been reported that these taxa can cause diseases in various crops. A high enrichment of these potential phytopathogenic fungi taxa may together with Fusarium oxysporum, the pathogen of cut chrysanthemum wilt, lead to the deterioration of cut chrysanthemum traits.

In addition, the measurement results of soil physical and chemical properties showed that continuous single cropping also significantly reduced the content of ammonium nitrogen in the soil, and the RDA analysis showed that it was the most important factor affecting the difference of community composition.

The study will help to understand the succession law of microbial communities in the rhizosphere soil of continuous cropping of cut chrysanthemum and the microbial mechanism of continuous cropping obstacles, and provide new ideas for the management of continuous cropping soil obstacles of cut chrysanthemum.

The research was funded by the National Natural Science Foundation of China (NSFC) and Science and Technology Innovation Project of CAAS .

Paper link:

https://doi.org/10.3389/fmicb.2022.801546