Control of Streptomyces alfalfae XY25T Over Clubroot Disease and Its Effect on Rhizosphere Microbial Community in Chinese Cabbage Field Trials

Abstract

Clubroot caused by Plasmodiophora brassicae is one of the most destructive diseases in cruciferous crops. Streptomyces alfalfae XY25T, a biological control agent, exhibited great ability to relieve clubroot disease, regulate rhizosphere bacterial and fungal communities in Chinese cabbage, and promote its growth in greenhouse. Therefore, field experiments were carried out to investigate the effects of S. alfalfae XY25T on clubroot and rhizosphere microbial community in Chinese cabbage. Results showed that the control efficiency of clubroot by S. alfalfae XY25T was 69.4%. Applying the agent can alleviate soil acidification; increase the contents of soil organic matter, available nitrogen, available phosphorus, and available potassium; and enhance activities of invertase, urease, catalase, and alkaline phosphatase. During Chinese cabbage growth, bacterial diversity decreased first and then increased, and fungal diversity decreased gradually after inoculation with S. alfalfae XY25T. High-throughput sequencing analysis showed that the main bacterial phyla were Proteobacteria, Bacteroidetes, Acidobacteria, and Planctomycetes, and the major fungal phyla were Ascomycota and Basidiomycota in rhizosphere soil. The dominant bacterial genera were Flavobacterium, Candidatus, Pseudomonas, Stenotrophomonas, Sphingomonas, Flavisolibacter, and Gemmatimonbacteria with no significant difference in abundance, and the major fungal genera were Monographella, Aspergillus, Hypocreales, Chytridiaceae, Fusarium, Pleosporales, Agaricales, Mortierella, and Pleosporales. The significant differences were observed among Pleosporales, Basidiomycota, Colletotrichum, two strains attributed to Agaricales, and another two unidentified fungi by using S. alfalfae XY25T. Moreover, quantitative real-time PCR results indicated that P. brassicae content was significantly decreased after the agent inoculation. In conclusion, S. alfalfae XY25T can affect rhizosphere microbial communities; therefore, applying the agent is an effective approach to reduce the damage caused by clubroot.

Multiomics Reveals the Effect of Root Rot on Polygonati Rhizome and Identifies Pathogens and Biocontrol Strain

“…The reduction in root-associated microbial diversity and the distinct changes in the microbial community were previously shown to be associated with disease occurrence ( 48 ). In general, a richer microbiota community composition has a stronger ability to control and reduce pathogens ( 49 , 50 ). Highly diverse microbial communities tend to be more complex and possess greater functional redundancy and interkingdom associations ( 16 , 51 ).…”

What Can We Learn from -Omics Approaches to Understand Clubroot Disease?

“…The soil microbiota also contribute to the outcome of the clubroot disease and were therefore studied in more detail. Analyses were done in either one condition [ 41 ], by comparing symptomatic vs. asymptomatic roots in the same field [ 42 ], resistant and susceptible cultivars [ 43 ], rotation patterns [ 44 ], or treatments with fungicides or biocontrol agents [ 45 , 46 , 47 ], and also virulent vs. avirulent pathotypes of P. brassicae on one host [ 48 ]. Only a few “multi-omics” approaches have been carried out, among them hormones and proteomes [ 3 ].…”

“…When such experiments are taken to the field alterations in the microbiome were seen when the plants were treated with Streptomyces alfalfae to reduce clubroot symptoms [ 46 ]. Such considerations are critical for long-term treatments in nature and their effect on the natural microbial populations.…”

Microbial Consortia: An Engineering Tool to Suppress Clubroot of Chinese Cabbage by Changing the Rhizosphere Bacterial Community Composition

“…Currently, the main method to control this disease is the application of fungicides, such as benzimidazoles, chlorothalonil, cyclophosphamide, and quintozene [ 3 ], resistant cultivars [ 7 ], crop rotation [ 8 ], and liming [ 9 ]. Many studies have reported that the excessive use of agrochemicals develops resistance in the pathogen and causes human-health concerns [ 10 , 11 ]. The resistant varieties may also lose their resistance against the pathogen due to the rapid mutation ability and strong pathogenicity of P. brassicae [ 12 ].…”

“…Liu et al reported that Bacillus subtilis XF-1 can produce antimicrobial compounds and suppress the incidence of clubroot disease up to 76.92% by improving the soil microbial diversity [ 17 ]. The application of Streptomyces alfalfae XY25 T improves soil health, regulates rhizospheric bacterial and fungal communities, enhances plant growth, and mitigates clubroot disease by up to 69.4% [ 11 ]. B. subtilis QST713 can reduce clubroot incidence in canola crops by up to 86% through the induction of host resistance and antibiosis [ 18 ].…”