The Phlorizin-Degrading Bacillus licheniformis XNRB-3 Mediates Soil Microorganisms to Alleviate Apple Replant Disease

Abstract

In this study, an endophytic phlorizin-degrading Bacillus licheniformis XNRB-3 was isolated from the root tissue of healthy apple trees, and its control effect on apple replant disease (ARD) and how it alleviates the pathogen pressure via changes in soil microbiomes were studied. The addition of strain XNRB-3 in Fusarium infested soils significantly reduced the number of pathogens in the soil, thus resulting in a lower disease incidence, and the relative control effect on Fusarium oxysporum reached the highest of 66.11%. The fermentation broth can also protect the roots of the plants from Fusarium oxysporum, Fusarium moniliforme, Fusarium proliferatum, and Fusarium solani infection. These antagonistic effects were further validated using an in vitro assay in which the pathogen control was related to growth and spore germination inhibition via directly secreted antimicrobial substances and indirectly affecting the growth of pathogens. The secreted antimicrobial substances were identified using gas chromatography-mass spectrometry (GC-MS) technology. Among them, alpha-bisabolol and 2,4-di-tert-butylphenol had significant inhibitory effects on many planted pathogenic fungi. Butanedioic acid, monomethyl ester, and dibutyl phthalate promoted root development of Arabidopsis plants. Strain XNRB-3 has multifarious plant growth promoting traits and antagonistic potential. In pot and field experiments, the addition of strain XNRB-3 significantly promoted the growth of plants, and the activity of enzymes related to disease resistance [superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)] was also significantly enhanced. It also reduced the abundance of four species of Fusarium and the content of phenolic acids in the rhizosphere soil, improved soil microbial community structure and nutritional conditions, and increased soil microbial diversity and activity, as well as the soil enzyme activity. The above results indicated that B. licheniformis XNRB-3 could be developed into a promising biocontrol and plant-growth-promoting agent.

Characterization of Bacillus amyloliquefaciens BA-4 and its biocontrol potential against Fusarium-related apple replant disease

“…Additionally, the B. licheniformis XNRB-3, isolated from root tissues, exhibited enduring colonization on the roots of apple seedlings. The introduction of the XNRB-3 strain may have a prolonged growth-promoting and biocontrol influence on apple plants confronted with the challenges of ARD (Duan et al, 2022b). In this study, the colonization ability of B. amyloliquefaciens BA-4 in MR seedling rhizosphere and its biocontrol effect on ARD were evaluated in the field to verify the findings obtained from pot experiments.…”

Identification of general features in soil fungal communities modulated by phenolic acids

“…The application of phenolic acid-degrading microbes could relieve continuous cropping obstacle, such as Xanthomonas and Rhizobium (Zhou et al, 2020) and Bacillus (Duan et al, 2022) resulted in the low phenolic acid contents that contributed to soil borne disease suppression. We found that Aspergillus and Fusarium were significantly enriched in the soil amended with high concentrations of all tested phenolic acids (Table 1), indicating their potential to efficiently degrade phenolic acids (Hegde et al, 2006).…”

Apple‐arbuscular mycorrhizal symbiosis confers resistance to Fusarium solani by inducing defense response and elevating nitrogen absorption

“…Paraffin sectioning and Periodic Acid Schiff staining of these root samples were carried out at the Keshang Biotech Co., Ltd. (Baso Diagnostics Inc., China). And the root sections were observed and photographed using transmission electron microscope (Philips Tecnai12‐TWIN) (Duan et al, 2022). We then divided the samples into the aboveground and underground components.…”

“…as the causal agent of ARD and confirmed Fusarium solani to be one of the major pathogens (Tang et al, 2022; Xiang et al, 2022). Researchers from different demographic regions have recently exploited various control measures, such as chemical, genetic and biological measures, to alleviate ARD (Duan et al, 2022). However, genetic and biological methods are the only effective approaches to control soil‐borne pathogens in a sustainable ecological environment.…”