Background The formation of symbiotic relationships between invasive plants and soil microorganisms in invaded regions, which enhances their adaptive capacity has been extensively studied. Bacillus, as a representative soil beneficial microorganism, can be recruited by invasive plants to their rhizosphere to promote growth. However, it remains unclear how dominant Bacillus species in the rhizosphere changes, and what feedback effects these changes may have, when invasive plants encounter biotic resistance in the invaded region, particularly from plant competition and insect herbivory. Results This study investigated the contents of Bacillus idriensis, B. mycoides, B. thuringiensis in the rhizosphere soil of Ageratina adenophora under different biotic resistance. It showed that B. idriensis exhibited the highest increase in the rhizosphere during plant competition, whereas B. thuringiensis showed the most significant increase under Aphis gossypii infestation. The effect of these Bacillus species on the competitive interactions between A. adenophora and native plant Rabdosia amethystoides were assessed. Inoculation with B. idriensis led to an 185.66% increase in biomass for monocultured A. adenophora and a 175.83% increase in mixed culture, thereby enhancing the positive effect of interspecific competition on the growth of A. adenophora. Additionally, the responses of A. adenophora to infestation by the generalist herbivorous A . gossypii following Bacillus inoculation were examined. B.thuringiensis inoculated significantly increased the levels of jasmonic acid, total phenols, flavonoids in A. adenophora infested by A. gossypii by 49.38%, 20.78%, 18.59%, while significantly reducing the survival rate and nymph density of A. gossypii, indicating enhanced resistance to the herbivore. B. idriensis improved the tolerance of A. adenophora to A. gossypii through growth promotion. Conclusion Our findings demonstrate that the abundance of distinct Bacillus species in the rhizosphere of A. adenophora varies in response to diverse biotic resistance encountered in the invaded region. These rhizobacterial interactions generate specific feedback effects that collectively enhance the invasiveness of the species.

Positive feedback effect of rhizosphere Bacillus on the growth and defense of Ageratina adenophora

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2025年12月5日

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Ewei Du,
Pengcun Li,
Yaping Chen,
Haihui Lin,
Qingbiao Xu,
Xi Huang,
Furong Gui

摘要

Background

The formation of symbiotic relationships between invasive plants and soil microorganisms in invaded regions, which enhances their adaptive capacity has been extensively studied. Bacillus, as a representative soil beneficial microorganism, can be recruited by invasive plants to their rhizosphere to promote growth. However, it remains unclear how dominant Bacillus species in the rhizosphere changes, and what feedback effects these changes may have, when invasive plants encounter biotic resistance in the invaded region, particularly from plant competition and insect herbivory.

Results

This study investigated the contents of Bacillus idriensis, B. mycoides, B. thuringiensis in the rhizosphere soil of Ageratina adenophora under different biotic resistance. It showed that B. idriensis exhibited the highest increase in the rhizosphere during plant competition, whereas B. thuringiensis showed the most significant increase under Aphis gossypii infestation. The effect of these Bacillus species on the competitive interactions between A. adenophora and native plant Rabdosia amethystoides were assessed. Inoculation with B. idriensis led to an 185.66% increase in biomass for monocultured A. adenophora and a 175.83% increase in mixed culture, thereby enhancing the positive effect of interspecific competition on the growth of A. adenophora. Additionally, the responses of A. adenophora to infestation by the generalist herbivorous A . gossypii following Bacillus inoculation were examined. B.thuringiensis inoculated significantly increased the levels of jasmonic acid, total phenols, flavonoids in A. adenophora infested by A. gossypii by 49.38%, 20.78%, 18.59%, while significantly reducing the survival rate and nymph density of A. gossypii, indicating enhanced resistance to the herbivore. B. idriensis improved the tolerance of A. adenophora to A. gossypii through growth promotion.

Conclusion

Our findings demonstrate that the abundance of distinct Bacillus species in the rhizosphere of A. adenophora varies in response to diverse biotic resistance encountered in the invaded region. These rhizobacterial interactions generate specific feedback effects that collectively enhance the invasiveness of the species.