Survival of the fittest: how the rice microbial community forces Sarocladium oryzae into pathogenicity

Microbial diversity and interactions: Synergistic effects and potential applications of Pseudomonas and Bacillus consortia

Microbial diversity and interactions in the rhizosphere play a crucial role in plant health and ecosystem functioning. Among the myriads of rhizosphere microbes, Pseudomonas and Bacillus are prominent players known for their multifaceted functionalities and beneficial effects on plant growth. The molecular mechanism of interspecies interactions between natural isolates of Bacillus and Pseudomonas in medium conditions is well understood, but the interaction between the two in vivo remains unclear. This paper focuses on the possible synergies between Pseudomonas and Bacillus associated in practical applications (such as recruiting beneficial microbes, cross-feeding and niche complementarity), and looks forward to the application prospects of the consortium in agriculture, human health and bioremediation. Through in-depth understanding of the interactions between Pseudomonas and Bacillus as well as their application prospects in various fields, this study is expected to provide a new theoretical basis and practical guidance for promoting the research and application of rhizosphere microbes.

Colorimetric loop-mediated isothermal amplification assay for detection and ecological monitoring of Sarocladium oryzae, an important seed-borne pathogen of rice

Accurate and timely disease detection plays a critical role in achieving sustainable crop protection. Globally, rice has been a staple crop for centuries plagued by the diseases that greatly hamper its productivity. Sheath rot, an emerging disease of rice caused by the seed-borne pathogen Sarocladium oryzae, has reportedly caused heavy losses to agricultural produce in recent years. Our study has led to the development and validation of a LAMP assay for early detection of S. oryzae, the causal agent of sheath rot from the live-infected tissues, seeds, weeds, and environmental samples. The assay could detect as low as 1.6 fg/μl of the pathogen in 15 min. The assay was implemented to bio-surveil the presence of this pathogen by testing it on three weed species (Echinochloa colona, Echinochloa crus-galli, and Cyperus teneriffae) growing around the rice fields. The results showed the presence of the pathogen in two of the weed species viz. E. colona and E. crus-galli. The assay was used to test 13 different rice varieties for the presence of S. oryzae in seeds. In total, three of the varieties did not show the presence of S. oryzae in their seeds while the rest were found to harbor the pathogen. The developed assay can effectively be used to detect and screen the presence of S. oryzae in live samples including seeds and field soil.

The unsung roles of microbial secondary metabolite effectors in the plant disease cacophony

Plants counter disease with an array of responses to styme pathogen ingress. In contrast to this cacophony, plant pathogens orchestrate a finely tuned repertoire of virulence mechanisms in their attempt to cause disease. One such example is the production of secondary metabolite effectors (SMEs). Despite many attempts to functionally categorize SMEs, their many roles in plant disease have proven they march to the beat of their producer's drum. Some lesser studied features of SMEs in plant disease include self-resistance (SR) and manipulation of the microbiome to enhance pathogen virulence. SR can be accomplished in three general compositions, with the first being the transport of the SME to a benign location; the second being modification of the SME so it cannot harm the producer; and the third being metabolic regulation of the SME or the producer homolog of the SME target. SMEs may also play an interlude prior to disease by shaping the plant microbial community, allowing producers to better establish themselves. Taken together, SMEs are integral players in the phytopathology canon.

A Novel In Planta Enrichment Method Employing Fusarium graminearum-Infected Wheat Spikes to Select for Competitive Biocontrol Bacteria

This work introduces an alternative workflow for the discovery of novel bacterial biocontrol agents in wheat against Fusarium head blight (FHB). Unlike the mass testing of isolate collections, we started from a diverse inoculum by extracting microbiomes from ears of field-grown plants at grain filling stage. Four distinct microbial communities were generated which were exposed to 3 14-day culture-independent experimental enrichments on detached wheat spikes infected with F. graminearum PH1. We found that one bacterial community reduced infection symptoms after 3 cycles, which was chosen to subsequently isolate bacteria through limiting dilution. All 94 isolates were tested in an in vitro and in planta assay, and a selection of 14 isolates was further tested on detached ears. The results seem to indicate that our enrichment approach resulted in bacteria with different modes-of-action in regard to FHB control. Erwinia persicina isolate C3 showed a significant reduction in disease severity (Fv/Fm), and Erwinia persicina C3 and Pseudomonas sp. B3 showed a significant reduction in fungal biomass (cGFP). However, the mycotoxin analysis of both these treatments showed no reduction in DON levels. Nevertheless, Pantoea ananatis H3 and H11 and Erwinia persicina H2 were able to reduce DON concentrations by more than 50%, although these effects were not statistically significant. Lastly, Erwinia persicina H2 also showed a significantly greater glucosylation of DON to the less phytotoxic DON-3G. The bacterial genera isolated through the enrichment cycles have been reported to dominate microbial communities that develop in open habitats, showing strong indications that the isolated bacteria can reduce the infection pressure of F. graminearum on the spike phyllosphere.