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Bacterial community shifts in Fusarium-induced avocado root rot and the antagonistic potential of Bacillus siamensis NB92

Summary

Avocado plants are threatened by a fungal disease called root rot that damages roots and reduces fruit production. Researchers discovered that when avocado roots become diseased, the beneficial bacteria in the soil around the roots decrease significantly. They isolated a beneficial bacterium called Bacillus siamensis NB92 from healthy avocado soil that can fight against the disease-causing fungus by producing special compounds. When applied to diseased soil, this bacterium reduced the fungal pathogen and protected avocado stems from damage, offering a natural alternative to chemical treatments.

Background

Avocado root rot caused by soil-borne fungi such as Fusarium spp. represents a major threat to global avocado production. The rhizosphere microbiome plays a critical role in plant health and disease suppression, yet the specific impacts of root rot on bacterial community dynamics remain poorly understood. Understanding how beneficial bacteria contribute to disease resistance is essential for developing effective biocontrol strategies.

Objective

This study aimed to characterize bacterial communities in healthy versus Fusarium-infested avocado soils using culture-independent 16S rRNA sequencing combined with culture-dependent isolation. The research focused on identifying key beneficial bacterial taxa with antagonistic potential against the root rot pathogen and evaluating their biocontrol efficacy.

Results

Root rot significantly reduced rhizosphere bacterial α-diversity and altered community structure, depleting beneficial phyla including Actinobacteriota and Firmicutes. Bacillus and Streptomyces abundance declined in diseased soils while Fusarium counts increased. Bacillus siamensis strain NB92 exhibited strong antagonistic activity against Fusarium sp. St7 through direct antagonism and VOC production, and successfully suppressed pathogen abundance in diseased soil.

Conclusion

The study reveals that avocado root rot disrupts beneficial bacterial communities critical for disease suppression. Bacillus siamensis NB92 represents a promising biocontrol agent that can effectively suppress Fusarium pathogens, offering a sustainable, microbiome-informed strategy for managing avocado root rot and reducing chemical dependency in agriculture.
  • Published in:Frontiers in Microbiology,
  • Study Type:Experimental Research Study,
  • Source: 40606151
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