Tea plants protected by a glowing shield representing enhanced defense

Unlocking Tea's Hidden Defenses: How a Common Compound Could Revolutionize Plant Disease Resistance

Kai Mendoza in Science & Nature September 2025 • 4 min read.

"New research reveals how benzothiadiazole boosts tea plants' natural defenses against a devastating fungal disease, offering a sustainable solution for farmers."

Tea, a beverage savored globally, faces constant threats from pests and diseases. Among these, Diplodia disease, caused by the fungus Lasiodiplodia theobromae, poses a significant challenge, particularly in regions like sub-Himalayan West Bengal, India. This disease can strike at any stage of the tea plant's development, jeopardizing yields and quality.

Plants, like all living organisms, possess their own defense mechanisms. When under attack, they activate various biochemical pathways to combat stress. One such pathway is the phenylpropanoid pathway, which produces protective compounds. Phenylalanine ammonia-lyase (PAL) is a crucial enzyme in this pathway, playing a key role in the synthesis of salicylic acid, a vital component of plant immunity.

Now, researchers are exploring innovative strategies to bolster these natural defenses. One promising approach involves using benzothiadiazole (BTH), a synthetic compound that mimics salicylic acid. By stimulating the plant's defense responses, BTH could offer a sustainable way to protect tea plants from Diplodia disease.

Decoding BTH's Defense-Boosting Power: How Does it Work?

Tea plants protected by a glowing shield representing enhanced defense

The study meticulously examined how BTH influences tea plants' defense mechanisms against L. theobromae. Scientists treated twelve-month-old tea seedlings with BTH and then inoculated them with the fungus. They then measured transcript accumulation – a measure of gene activity – in treated and untreated plants, both with and without inoculation.

The results were compelling. Plants treated with BTH and inoculated with L. theobromae exhibited significantly higher transcript accumulation compared to untreated controls. This indicated that BTH effectively activated the plants' defense genes. Moreover, these treated plants showed a reduced disease index, meaning they were better able to resist the fungal infection.

Higher Transcript Accumulation: BTH-treated and L. theobromae-inoculated plants showed a transcript accumulation of 3.81 µg/µl, compared to 3.26 µg/µl in untreated controls.
Reduced Disease Index: The disease index in BTH-treated plants was 3.8 ± 0.02, significantly lower than the 14.6 ± 0.05 in untreated controls.
Increased PAL Activity: PAL activity increased from 2.5 to 4.4 µmol min¯¹ g¯¹ in treated-inoculated plants, compared to 2.5 to 2.7 µmol min¯¹ g¯¹ in healthy controls.

Further analysis revealed the intricate details of how BTH exerts its protective effects. Sequencing and comparing nucleotide and protein sequences allowed researchers to establish the 3D structure of the PAL enzyme, identifying three key lyase superfamily motifs. Notably, the increase in PAL activity was observed in treated-inoculated plants, further supporting the role of BTH in boosting the plant's defense response.

A Greener Future for Tea: The Promise of BTH

These findings suggest that BTH holds significant potential as a tool for enhancing disease resistance in tea plants. By triggering the plant's natural defenses, BTH could reduce the reliance on synthetic pesticides, promoting more sustainable and environmentally friendly tea cultivation practices. This research opens new avenues for protecting crops and ensuring the continued availability of this beloved beverage for generations to come.

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Everything You Need To Know

What is Diplodia disease and why is it a problem for tea plants?

Diplodia disease is a significant threat to tea plants caused by the fungus *Lasiodiplodia theobromae*. It can affect the plants at any stage of development, leading to reduced yields and lower quality tea. Understanding the mechanisms of this disease is crucial for developing effective strategies to protect tea crops and maintain tea production.

What is benzothiadiazole (BTH) and why is it important in protecting tea plants?

Benzothiadiazole (BTH) is a synthetic compound that mimics salicylic acid, a natural plant hormone involved in defense responses. BTH is important because it can be used to stimulate a tea plant's defense mechanisms against diseases like Diplodia. By activating these defenses, BTH could potentially reduce the need for synthetic pesticides, offering a more sustainable approach to tea cultivation. Further research is needed to fully understand the long-term effects and optimal application methods of BTH.

What is the phenylpropanoid pathway and why is Phenylalanine ammonia-lyase (PAL) important?

The phenylpropanoid pathway is a biochemical pathway in plants that produces protective compounds. Phenylalanine ammonia-lyase (PAL) is a key enzyme in this pathway, and is particularly important because it plays a crucial role in the synthesis of salicylic acid, which is a vital component of plant immunity. Enhancing the phenylpropanoid pathway and PAL activity can help tea plants better defend themselves against pathogens.

What does 'transcript accumulation' mean in the context of plant defense, and why is it relevant?

Transcript accumulation refers to the increase in the amount of RNA molecules produced from specific genes. Higher transcript accumulation indicates that genes related to defense responses are being actively expressed. In the context of the study, a higher transcript accumulation in tea plants treated with benzothiadiazole (BTH) and inoculated with *L. theobromae* suggests that BTH effectively activates the plant's defense genes, enabling them to resist the fungal infection.

What is the 'disease index' and what does it tell us about plant health?

The disease index is a measure used to quantify the severity of a disease in plants. A lower disease index indicates that the plants are better able to resist the infection. The study found that tea plants treated with benzothiadiazole (BTH) had a significantly lower disease index when infected with *L. theobromae*, which suggests that BTH helps to enhance the plant's resistance to Diplodia disease. Measuring the disease index is essential for evaluating the effectiveness of disease control strategies.