Assessment of Brown Spot Disease (Bipolaris oryzae) Severity in Paddy Fields of Prayagraj District, Uttar Pradesh, India
Abstract
Brown spot disease, caused by the fungus Bipolaris oryzae, poses a significant threat to rice production. This study assessed the severity and distribution of the disease in the paddy fields of the Prayagraj district, Uttar Pradesh, India, over two consecutive Kharif seasons (September 2011 and September 2012). A survey was conducted across eight tehsils (Karchhana, Soraon, Handia, Phulpur, Bara, Meja, Sadar, and Koraon), with five villages randomly selected from each. Disease severity was quantified using the Percent Disease Incidence (PDI) method. The pooled mean PDI across the tehsils ranged from alow of 25.08% in Phulpur to a high of 47.24% in Meja. High disease incidence was also noted in Soraon (45.57%). The village-level data revealed the highest pooled PDI of 50.0% in Dihi Khurd (Meja) on the PB-1509 variety. The disease was prevalent during both the Post tillering and Panicle initiation stages. The consistent and high incidence of brown spot disease in tehsils like Meja and Soraon confirms its endemic status in the region and underscores the urgent need for targeted integrated disease management strategies, including the development and deployment of resistant rice varieties.
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Introduction
Rice (Oryza sativa L.)is a staple food for more than half of the world'spopulation and is critical to global food security [1]. In India, rice is the most important food crop, and its production is vital for the country'seconomy and sustenance. However, rice production is constantly threatened by various biotic and abiotic stresses. Among the biotic stresses, fungal diseases are a major limiting factor, with brown spot disease being one of the most destructive [2] [3].
Brown spot disease, caused by the ascomycete fungus Bipolaris oryzae (teleomorph: Cochliobolus miyabeanus), affects the rice plant at all growth stages, from the seedling to the grain-filling stage [4]. The characteristic symptoms include oval to circular spots on the leaves, which are initially dark brown and later develop a greyish-white center with a reddish-brown margin. Severe infection leads to premature leaf senescence, reduced photosynthetic efficiency, and poor grain filling, resulting insignificant yield losses, which can range from 1% to 34% in various parts of Asia and Africa [5]. The severity of brown spot disease is highly influenced by environmental factors, particularly high humidity and temperature, as well as host factors such as varietal susceptibility and nutritional status of the plant, especially nitrogen and potassium deficiency [6]. Given the significant economic impact of the disease, regular monitoring and assessment of its incidence and severity are crucial for effective disease management planning. This study aimed to determine the prevalence and severity of brown spot disease in the major rice-growing areas of the Prayagraj district, Uttar Pradesh, over two consecutive years, providing essential data for regional disease control efforts.
Conclusion
The study successfully quantified the severity of brown spot disease in the Prayagraj district, identifying Meja and Soraon as the tehsils with the highest disease incidence. The consistent presence of the disease over two years, coupled with high PDI values in specific villages and varieties, underscores the urgent need for effective disease management. Future research should focus on the correlation between soil nutrient status, specific environmental parameters, and the observed disease severity to develop an integrated pest management (IPM) strategy that includes the use of resistant varieties, balanced fertilization, and timely fungicide application. CONFLICT OF INTEREST The authors declare no conflict of interest.
