Guwahati: In a ground-breaking discovery, scientists have identified Pseudopestalotiopsis ampullacea as a new fungal pathogen responsible for gray blight disease in tea (Camellia sinensis). This is the first documented instance of this pathogen affecting tea crops in India, posing a serious challenge to one of the nation’s most significant agricultural industries.
The study, conducted by researchers from the Tea Research Association’s North Bengal R&D Center, focused on tea plantations in North Bengal. The findings, recently published in Scientific Reports, have far-reaching implications for tea cultivation, disease management, and crop sustainability in India.
The threat of Gray Blight
Gray blight is a destructive disease that affects tea plants in major tea-producing countries, including China, India, and Sri Lanka. It primarily targets old and mature leaves, causing necrotic spots that spread to form concentric rings with gray-white centers and brown margins. In severe cases, the disease can decimate the entire leaf canopy, drastically reducing yield and quality.
While gray blight has been linked to several fungal species in the Pseudopestalotiopsis, Neopestalotiopsis, and Pestalotiopsis genera, Pseudopestalotiopsis ampullacea had previously been reported only in China. Its presence in Indian tea plantations signals a new and serious threat to the country’s tea industry, which produces approximately 1.3 million metric tons annually and supports millions of livelihoods.
Scientific breakthrough
Researchers collected gray blight-symptomatic tea leaves from plantations in Nagrakata, West Bengal, and conducted detailed morphological, cultural, and molecular analyses under a project funded by the Department of Science and Technology, Government of India. Using multi-locus phylogenetic techniques, they confirmed the pathogen’s identity as P. ampullacea.
The study revealed variability in the pathogen’s impact on different tea cultivars. Among the 25 cultivars tested, TV11 showed resistance, while TV1, TV9, and Naxalbari were highly susceptible. This variation highlights the potential for breeding resistant cultivars but also underscores the urgency of implementing effective management strategies.
Combatting the disease
To mitigate the threat posed by P. ampullacea, researchers evaluated the efficacy of synthetic fungicides and microbial bioagents in laboratory settings. Their findings offer promising solutions:
Synthetic Fungicides: Systemic fungicides such as carbendazim + mancozeb, propiconazole, and hexaconazole proved highly effective, achieving more than 69.1% inhibition. Copper oxychloride also showed significant efficacy.
Microbial Bioagents: Native microbial agents such as Trichoderma harzianum, T. reesei, and Bacillus subtilis, isolated from tea rhizospheres by TRA Nagrakata, demonstrated significant antagonistic activity against the pathogen, with inhibition rates exceeding 66.6%. These bioagents present environmentally sustainable alternatives to chemical fungicides.
Implications for the Tea Industry
This research represents a major advancement in understanding and managing gray blight disease in tea. The identification of resistant cultivars like TV11 and the demonstrated effectiveness of certain fungicides and bioagents provide critical tools for combating the disease.
“Gray blight caused by Pseudopestalotiopsis ampullacea poses a significant threat to tea production in India. Our findings not only identify this new pathogen but also offer actionable solutions for its management,” said Dr. Abhay K. Pandey, the lead researcher.
The research team is also working on a broader study of Pestalotiopsis-like species involved in tea gray blight in North Bengal and Assam. They aim to assess their sensitivity to various PPC-approved fungicides and identify additional management solutions.
However, the study emphasizes the need for field trials to validate the efficacy of these management strategies under real-world conditions. Researchers also advocate further investigations into the genetic mechanisms behind resistance in certain cultivars, which could inform breeding programs aimed at developing gray blight-resistant tea varieties.
The Indian tea industry, already under pressure from climate change and fluctuating market dynamics, must act swiftly to address this new threat. By integrating synthetic and biological control measures with the development of resistant cultivars, the industry can mitigate the impact of gray blight and ensure sustainable production.
This discovery is a wake-up call for tea-producing nations worldwide. As pathogens evolve and spread, proactive research and integrated pest management are critical to protecting crops that form the backbone of millions of livelihoods and economies.
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