Plant-associated Bacillus and Pseudomonas antimicrobial activities in plant disease suppression via biological control mechanisms - A review

This review deals with the mechanism of antagonistic action of bacterial and fungal biocontrol agents such as the production of antibiotics, siderophores, enzyme secretion, competition for nutritio...

Biological control: a sustainable and practical approach for plant disease management

Phytopathogens causing mycotoxicoses in maize are a potential threat to grain quality and availability in many maize producing countries including South Africa The use of natural biological agents for controlling maize fusariosis and many other such plant diseases, as opposed to the more traditional use of chemicals, is growing in popularity globally, as a greater emphasis gets placed on public health In this study, nine Fusarium inhibiting isolates representing a subset of 200 native Pseudomonas isolates from the maize rhizosphere of 10 different farms in the North West Province of South Africa were further evaluated for their in vitro biocontrol potential Although few of the isolates (PS11, PS122, PS22, PS64, PS68, PS72, PS83, PS86, and PS91) had impressive in vitro biosuppressive effects against Fusarium graminearum and Fusarium culmorum, while also producing biosurfactants, only isolate HARBPS91 showed consistent antifungal capacity along with maize seed bioprotection capability The candidate antagonist HARBPS91 was molecularly characterized as a Pseudomonas fulva strain and was found to harbor multiple functional biosynthetic gene clusters after FTIR, NMR and ESI-Q-TOF-MS metabolomics investigation P fulva HARBPS91 bioprotective mechanism is attributed to the possible presence of hydrogen cyanide, pyrrolnitrin, and rhamnolipids

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Pseudomonas fulva HARBPS9.1: candidate anti-Fusarium agent in South Africa

Angelica sinensis (Oliv.) Diels (A. sinensis) is a Chinese herb grown in different geographical locations. It contains numerous active components with therapeutic value. Rhizosphere microbiomes affect various aspects of plant performance, such as nutrient acquisition, growth and development and plant diseases resistance. So far, few studies have investigated how the microbiome effects level of active components of A. sinensis. This study investigated whether changes in rhizosphere microbial communities and metabolites of A. sinensis vary with the soil microenvironment. Soils from the two main A. sinensis-producing areas, Gansu and Yunnan Province, were used to conduct pot experiments. The soil samples were divided into two parts, one part was sterilized and the other was unsterilized planting with the seedling variety of Gansu danggui 90–01. All seedlings were allowed to grow for 180 days. At the end of the experiment, radix A. sinensis were collected and used to characterize growth targets and chemical compositions. Rhizosphere soils were subjected to microbial analyses. Changes in metabolic profiles and rhizosphere microbial communities of A. sinensis grown under different soil microenvironments were similar. The GN (Gansu non-sterilized), YN (Yunnan non-sterilized), GS (Gansu sterilized), and YS (Yunnan sterilized) groups were significantly separated. Notably, antagonistic bacteria such as Sphingomonas, Pseudomonas, Lysobacter, Pseudoxanthomonas, etc. were significantly (p < 0.05) enriched in Gansu soil compared with Yunnan soil. Moreover, senkyunolide I and ligustilide dimers which were enriched in GS group were strongly positively correlated with Pseudomonas parafulva; organic acids (including chlorogenic acid, dicaffeoylquinic acid and 5-feruloylquinic acid) and their ester coniferyl ferulate which were enriched in YS Group were positively associated with Gemmatimonadetes bacterium WY71 and Mucilaginibater sp., respectively. The soil microenvironment influences growth and level/type of active components in A. sinensis. Further studies should explore the functional features of quality-related bacteria, identify the key response genes and clarify the interactions between genes and soil environments. This will reveal the mechanisms that determine the quality formation of genuine A. sinensis.

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Insights into the mechanism of the effects of rhizosphere microorganisms on the quality of authentic Angelica sinensis under different soil microenvironments

Y.H. Lee

Papers

Analysis of traits for biocontrol performance of Pseudomonas parafulva JBCS1880 against bacterial pustule in soybean plants