Abscisic Acid Metabolizing Rhodococcus sp. Counteracts Phytopathogenic Effects of Abscisic Acid Producing Botrytis sp. on Sunflower Seedlings

Summary

Scientists discovered that a beneficial soil bacterium can protect sunflower plants from a harmful fungus by eating the toxin the fungus produces. The fungus normally weakens plant defenses by producing a chemical called abscisic acid, but the bacterium metabolizes this chemical and prevents it from harming the plant. This approach works without the bacterium directly killing the fungus, offering a new way to protect crops from disease.

Background

Phytopathogenic fungi like Botrytis produce abscisic acid (ABA) to suppress plant defense responses. Plant growth-promoting rhizobacteria (PGPR) can metabolize phytohormones, but their role in counteracting fungal ABA remains poorly understood. This study explores whether ABA-metabolizing rhizobacteria can alleviate pathogenic effects of ABA-producing fungi.

Objective

To investigate whether ABA-metabolizing Rhodococcus sp. P1Y can counteract the phytopathogenic effects of ABA-producing Botrytis sp. BA3 on sunflower seedlings. The study also examines hormonal changes in plants subjected to fungal infection and bacterial inoculation.

Results

Rhodococcus sp. P1Y successfully metabolized fungal ABA without exhibiting antifungal activity. Inoculation with P1Y eliminated negative effects of Botrytis sp. BA3 and exogenous ABA on root growth by reducing root ABA concentrations. Both microorganisms significantly modulated hormonal status, affecting IAA, SA, JA, GA3 and cytokinin concentrations.

Conclusion

The results demonstrate a novel biocontrol mechanism whereby ABA-metabolizing rhizobacteria counteract ABA-producing phytopathogenic fungi through metabolism of fungal ABA rather than direct antagonism. This finding expands understanding of PGPR-mediated biocontrol mechanisms and suggests potential applications for protecting plants against necrotrophic pathogens.
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