RESUMEN
Background: Plasmodiophora brassicae is an ever-increasing threat to cruciferous crop production worldwide. Aims and methods: This study investigated the impact of pre-soil fumigation with ammonium bicarbonate (N) and lime (NB) to manage clubroot disease in Chinese cabbage through 16S rRNA gene amplification sequencing. Results: We found that soil fumigation with N and NB suppressed disease incidence by reducing the soil acidity and population of P. brassicae in the rhizosphere. Minimum disease incidence and maximum relative control effect of about 74.68 and 66.28% were achieved in greenhouse and field experiments, respectively, under the combined application of ammonium bicarbonate and lime (LNB) as compared with N, NB, and control (GZ). Microbial diversity analysis through Miseq sequencing proved that pre-soil fumigation with N, NB, and LNB clearly manipulated rhizosphere microbial community composition and changed the diversity and structure of rhizosphere microbes compared with GZ. Bacterial phyla such as Proteobacteria, Bacteriodetes, and Acidobacteria and fungal phyla including Olpidiomycota and Ascomycota were most dominant in the rhizosphere of Chinese cabbage plants. Soil fumigation with N and NB significantly reduced the abundance of clubroot pathogen at genus (Plasmodiophora) level compared with GZ, while decreased further under combined application LNB. Microbial co-occurrence network analysis showed a highly connected and complex network and less competition for resources among microbes under combined application LNB. Conclusion: We conclude that for environmentally friendly and sustainable agriculture, soil fumigation with combined ammonium bicarbonate and lime plays a crucial role in mitigating Chinese cabbage clubroot disease by alleviating soil pH, reducing pathogen population, and manipulating the rhizosphere microbiome.
RESUMEN
Clubroot caused by Plasmodiophora brassicae is an economically important soilborne disease of Chinese cabbage worldwide. Integrated biological control through crop rotation is considered a good disease management approach to suppress the incidence of soilborne diseases. In this study, we evaluated the effect of a marigold plant (root exudates, crude extract, and powder) on the germination and death of resting spores of P. brassicae in vitro assays. Additionally, we also performed 16S high throughput sequencing, to investigate the impact of marigold-Chinese cabbage crop rotation on soil bacterial community composition, to manage this devastating pathogen. This study revealed that the marigold root exudates, crude extract, and powder significantly promoted the germination and death of P. brassicae resting spores. Under field conditions, marigold-Chinese cabbage crop rotation with an empty period of at least 15 days enhanced the germination of P. brassicae resting spores, shifted the rhizosphere bacterial community composition, and suppressed the incidence of clubroot by up to 63.35%. Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, and Verrucomicrobia were the most dominant phyla and were present at high relative levels in the rhizosphere soil of Chinese cabbage. We concluded that crop rotation of Chinese cabbage with marigold can significantly reduce the incidence of clubroot disease in the next crop. To our knowledge, this is the first comprehensive study on the prevention and control of clubroot disease in Chinese cabbage through crop rotation with marigold.
RESUMEN
Clubroot disease, caused by Plasmodiophora brassicae, is a serious threat to Chinese cabbage (Brassica rapa subsp. pekinensis) production, which results in extensive yield losses. At present, clubroot control mainly depends upon pesticides, which provoke food-safety concerns, and the application of sole biocontrol agents cannot successfully control the disease. In this study, we investigated the effect of Bacillus cereus BT-23, Lysobacter antibioticus 13-6, and Lysobacter capsici ZST1-2 as sole strains, intra-/inter-genus co-culture, and microbial consortia on clubroot disease, plant growth, and rhizosphere bacterial diversity in a field experiment. The microbial consortia efficiently controlled the incidence of clubroot disease, with a biocontrol effect of about 65.78%, by decreasing the soil acidity and enhancing the yield (17,662.49 kg/acre). The high-throughput sequencing results demonstrated that the phyla Proteobacteria and Bacteroidetes were present in high relative abundance in the rhizosphere soil of the Chinese cabbage. Furthermore, Firmicutes was found as a unique phylum in the rhizosphere soil of CK-H and T1-T7, except for CK-D. The application of microbial consortia recovers the imbalance in indigenous microbial communities. Therefore, we conclude that microbial consortia can reduce the clubroot incidence in Chinese cabbage by decreasing the soil acidity and altering the diversity and structure of rhizosphere bacterial communities. This study highlights the potential of microbial consortia as an engineering tool to control devastating soilborne diseases in commercial crops.
