An interpretative review on a catastrophic pathogen Bipolaris oryzae causing rice brown spot disease
2025
Sudhasha, S | SureshKumar, S M | Srinivasaperumal, A P | Kanaka, S | Vennila, S | Jayachitra, J | Rani, T | Vijayapriya, M | Mahalakshmi, S | Bhuvaneswari, R | Karan, R | Sankar, J | Kannan, R | Balabaskar, P | Sanjeevkumar, K
Bipolaris oryzae, (Telomorph: Cochiliobolus miyabianus) the pathogen responsible for rice brown spot disease, had a significant historical impact, notably contributing to the Bengal famine of 1943, which resulted in reduced rice yields and approximately 3 million deaths from starvation. As a polycyclic pathogen, B. oryzae spreads through seeds and airborne conidia (anamorphic stage), causing secondary infections in both nurseries and fields. Seed-borne infections worsen disease severity, while airborne conidia accelerate disease spread. B. oryzae shows variability in colony characteristics influenced by growth medium, geography and environmental conditions. Its morphological variability, including a range of conidial sizes, shapes and colors, increases its resilience and ensures its survival across diverse environments. Additionally, the pathogen's molecular variability allows it to adapt and overcome plant resistance mechanisms. B. oryzae produces host-specific toxins, such as cochliobolin and ophiobolin, which disrupt plant defense mechanisms and inhibit growth, particularly affecting roots, coleoptiles and leaves. Due to its broad adaptability to different climates, it remains a persistent and resilient threat in rice-growing regions worldwide. Epidemiological studies offer valuable insights into the pathogen's initiation, survival and distribution. This review highlights the importance of understanding the pathogen's variability, toxicity and mechanisms of disease spread, all of which complicate control efforts. Effective integrated management strategies are essential to mitigate the devastating impact of rice brown spot disease on global rice production.
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