First report of Colletotrichum fructicola causing anthracnose on Rosa sp. in Thailand and the control strategies
This study reports the first identification of *Colletotrichum fructicola* as an anthracnose pathogen on roses in Thailand and demonstrates that the biocontrol bacterium *Bacillus amyloliquefaciens* TU-Orga12, which produces surfactin and specific volatile organic compounds, offers superior disease control compared to the chemical fungicide mancozeb in both greenhouse and commercial production settings.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
The Problem: Roses in Thailand Have a New Enemy
Imagine the rose gardens in Thailand as a beautiful, high-stakes fashion show. Everyone wants the perfect blooms. But recently, a new "villain" has crashed the party.
The researchers discovered a specific fungus called Colletotrichum fructicola attacking roses in Thailand. Before this study, this fungus was known to attack over 90 other types of plants (like peppers and papayas), but it had never been officially caught on a rose in Thailand. Think of it like a burglar who has been stealing from houses all over town, but this is the first time they've been caught breaking into a specific, high-end jewelry store (the rose).
This fungus causes "anthracnose," which is basically a nasty skin infection for plants. It leaves ugly brown spots, makes leaves turn yellow, and can ruin the whole plant.
The Investigation: Who is the Bad Guy?
The team went to a rose farm in Chiang Mai, collected sick leaves, and grew the fungus in a lab to see what it looked like. They used a "molecular ID check" (DNA sequencing) to confirm the identity.
- The Verdict: It is definitely Colletotrichum fructicola.
- The Evidence: Under a microscope, the fungus looked like a tiny, smooth, white-and-gray army with special spores (its "soldiers") ready to spread.
The Battle Plan: Chemicals vs. Nature
Once they knew who the enemy was, the team tried to figure out how to stop it. They tested two main strategies: the "Big Stick" (chemicals) and the "Good Cop" (nature).
1. The Big Stick: Chemical Fungicides
They tested four common chemical sprays to see which one could stop the fungus from growing in a petri dish.
- The Winner: A chemical called Mancozeb. It was the strongest, stopping about 41% of the fungus's growth.
- The Loser: Another chemical called Carbendazim barely did anything (only 2.5% inhibition).
- The Catch: While chemicals work, they can be bad for the environment and human health. Plus, the fungus might eventually learn to ignore them (resistance).
2. The Good Cop: Biological Control (The Hero Bacteria)
Instead of poison, the researchers looked for a "good guy" bacteria to fight the "bad guy" fungus. They tested six different strains of bacteria from the Bacillus family (a group known for being tough and helpful).
- The Star Player: One specific strain, Bacillus amyloliquefaciens TU-Orga12, was the clear champion.
- How it fought:
- Direct Attack: In the lab, this bacteria grew right next to the fungus and stopped it from spreading, cutting its growth by about 44%.
- The Secret Weapons: The bacteria didn't just sit there; it fired chemical missiles.
- Surfactin: A liquid soap-like substance (9.87 mg per liter) that disrupts the fungus's cell walls.
- Volatile Organic Compounds (VOCs): Imagine the bacteria wafting a "bad smell" that the fungus can't stand. The study identified specific "smells" like guaiacol (which smells like wood smoke) and 2,5-dimethylpyrazine. These airborne chemicals stopped the fungus from growing and even stopped it from making new spores (babies).
The Real-World Test: Greenhouse and Farm
The researchers didn't stop at the lab. They took their hero bacteria to real rose plants.
- In the Greenhouse: They sprayed the bacteria on rose leaves before infecting them with the fungus.
- Result: The roses treated with the bacteria stayed much healthier. The disease severity dropped significantly compared to the untreated plants.
- On the Commercial Farm: They tested the bacteria on a real rose farm where the plants were already getting sick naturally.
- Result: The bacteria (TU-Orga12) was even better than the chemical Mancozeb in the long run. While the chemical-treated plants eventually got very sick (97% disease severity), the bacteria-treated plants stayed relatively healthy (only 57% severity). The bacteria kept the disease from spreading as fast.
The Conclusion: A New Way to Save Roses
This paper claims that:
- Colletotrichum fructicola is a new confirmed enemy of roses in Thailand.
- Mancozeb is the best chemical currently available to fight it, but it has limits.
- Bacillus amyloliquefaciens TU-Orga12 is a powerful, eco-friendly alternative. It fights the fungus by:
- Blocking it physically.
- Shooting it with "soap" (surfactin).
- Bombarding it with "bad smells" (VOCs) that stop it from growing and reproducing.
- Helping the rose plant get stronger and fight back on its own.
The study suggests that instead of just relying on harsh chemicals, farmers can use this specific bacteria as a "bodyguard" for their roses, keeping them healthy and the environment safe.
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