A team of scientists from Sophia University (Japan), led by Professor Tamao Saito, has discovered that the slime mold Dictyostelium discoideum secretes organic compounds capable of repelling root-knot nematodes (RKN), parasites that attack plant roots and cause multimillion-dollar agricultural losses.
The research, published in Journal of Agricultural and Food Chemistry, opens new possibilities for the development of ecological pesticides.
Root-knot nematodes: a global threat to crops
They are estimated to cause annual losses of 173 billion dollars worldwide.
RKN (Meloidogyne spp.) are microscopic worms that infect plant roots, causing wilting, weakening, and death.
Although chemical pesticides can control them, they also destroy beneficial microorganisms and reduce soil fertility, creating an urgent need for sustainable alternatives.
Conditioned medium: an innovative technique to extract repellent compounds
The team used a procedure called “conditioned medium” (CM), which involves collecting mold cells from the culture, suspending them in buffered water, drying them, and redissolving them. This extract showed very potent repellent effects:
- At 30 mg/mL: 99% of the eggs did not hatch, and almost all juveniles died
- At 3 mg/mL: 81% of the eggs did not hatch, and 71% of the juveniles died
Moreover, in tomato seedling trials, daily treatment with CM protected the roots for two months and improved the aerial growth of the plants.
Chemical composition: 14 compounds with synergistic effect
The mixture is more effective than individual compounds and does not affect soil health.
The analysis revealed 14 organic compounds with repellent capacity:
- 4 L-type amino acids
- 5 carboxylic acids
- 3 antioxidants
- Norepinephrine and pyridoxine
The synergistic combination of these compounds was highly effective: only 0.01 mg of the mixture achieved the same effect as 5 mg of CM, demonstrating its potency and efficiency. Being natural, they are expected to have minimal impact on soil fertility.
Towards sustainable and toxin-free agriculture
The slime mold could be integrated into pest management strategies. “These compounds can contribute to sustainable food production and better soil health,” says Professor Saito.
The team plans to investigate the genetic mechanisms that induce repulsion in RKN, and explore how multiple signaling pathways could enhance the repellent effect. This approach aligns with the principles of integrated pest management, which aims to reduce chemical use and preserve soil biodiversity.
