Assessing Yield Losses Caused by Rice Tungro Virus: A Comprehensive Review

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Jabeen Asma , Subrahmanyam D , Krishnaveni D

ICAR-Indian Institute of Rice Research, Rajendranagar, Hyderabad-500 030, Telengana State, India.

Corresponding Author Email: asma.aman5@gmail.com

DOI : https://doi.org/10.51470/AGRI.2022.1.1.12

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Introduction

Rice (Oryza sativa L.) is a staple food for over half of the world’s population, particularly in Asia where it serves as a primary source of nourishment and livelihood for millions of people. However, rice production faces numerous challenges, among which viral diseases pose a significant threat to crop health and productivity [1-2]. Rice tungro virus (RTV) stands out as one of the most devastating viral pathogens affecting rice cultivation, causing substantial yield losses and economic hardships for farmers across regions where rice is cultivated. Rice (Oryza sativa L.) stands as one of the most vital cereal crops worldwide, serving as a staple food for billions of people, particularly in Asia. However, rice production faces a multitude of challenges, including biotic stresses such as viral diseases, which can substantially impact yields and threaten food security [3]. Among these viral diseases, rice tungro virus (RTV) emerges as a significant concern, particularly in regions where rice cultivation is prevalent. RTV, a member of the Fijivirus genus in the Reoviridae family, presents a complex challenge due to its interaction with insect vectors, primarily the green leafhopper (Nephotettix virescens) and the brown planthopper (Nilaparvata lugens), which transmit the virus during feeding. This transmission mechanism, coupled with factors like susceptible rice cultivars and conducive environmental conditions, contributes to the widespread occurrence of RTV and its detrimental effects on rice yields [4]. The symptoms of RTV infection manifest in various forms, including stunting, leaf discoloration, reduced tillering, and diminished panicle development. These symptoms not only compromise yield quantity but also affect grain quality, further exacerbating the economic losses incurred by farmers. In regions where rice cultivation is a cornerstone of livelihoods, the impact of RTV extends beyond economic implications to social and food security concerns, underscoring the urgency for effective management strategies. Efforts to manage RTV encompass a multifaceted approach, integrating cultural, biological, and chemical methods to minimize disease incidence and mitigate yield losses [5]. Plant breeding programs have played a pivotal role in developing RTV-resistant rice varieties, leveraging both conventional and molecular breeding techniques to enhance genetic resistance to the virus. Furthermore, cultural practices such as crop rotation, timely planting, and the use of certified seeds contribute to disease management by reducing the build-up of viral inoculum and optimizing crop health.

Despite advancements in RTV management, challenges persist, including the emergence of new virus strains, the development of insecticide resistance in vector populations, and the need for sustainable, environmentally friendly practices [6]. Continued research efforts aimed at understanding the genetic basis of RTV resistance, unraveling the complexities of vector-virus-plant interactions, and exploring novel control measures are imperative to address these challenges and ensure the resilience of rice production systems, this review aims to provide a comprehensive analysis of the impact of RTV on rice production, encompassing its epidemiology, symptomatology, transmission dynamics, and management strategies [7]. By synthesizing existing knowledge and identifying research gaps, this review seeks to inform future research directions, policy formulation, and on-the-ground interventions aimed at mitigating the adverse effects of RTV and enhancing the sustainability of rice cultivation systems, RTV poses a formidable challenge to global rice production, underscoring the importance of collaborative efforts among researchers, policymakers, and practitioners to develop holistic and sustainable solutions that safeguard food security and livelihoods in rice-growing regions.

Epidemiology and Symptoms

RTV belongs to the genus Fijivirus within the family Reoviridae and is transmitted primarily by two insect vectors, the green leafhopper (Nephotettix virescens) and the brown planthopper (Nilaparvata lugens) [8]. These vectors acquire the virus during feeding on infected rice plants and subsequently transmit it to healthy plants during subsequent feeding activities. The complex interactions between the virus, its insect vectors, and the rice plant contribute to the persistence and spread of RTV within rice-growing regions. Symptoms of RTV infection vary depending on rice cultivar, environmental conditions, and the stage of plant development. Typical symptoms include stunting, yellowing or reddening of leaves, reduced tillering, and decreased panicle size. Severe infections can lead to complete crop loss, exacerbating food insecurity and economic instability in affected areas [9].

Management Strategies

The management of RTV involves integrated approaches aimed at reducing viral transmission, enhancing host resistance, and implementing cultural practices to minimize disease incidence and severity [10]. Planting resistant rice varieties has been a key strategy in combating RTV, with breeding programs focusing on developing cultivars with durable resistance to multiple strains of the virus [11]. Additionally, the use of insecticides to control vector populations, cultural practices such as early planting and maintaining proper field hygiene, and the promotion of alternative cropping systems have shown promise in reducing RTV incidence and mitigating yield losses.

Emerging Trends and Future Directions

Recent advancements in molecular biology and biotechnology have facilitated the identification of genetic markers associated with RTV resistance, accelerating the development of resistant rice varieties through marker-assisted selection and genetic engineering techniques [12]. Moreover, interdisciplinary research efforts integrating agronomic, ecological, and socioeconomic perspectives are essential for developing holistic approaches to RTV management that are sustainable, cost-effective, and socially equitable [13]. RTV remains a formidable challenge to rice production, necessitating continued research efforts and collaborative initiatives to develop effective management strategies and build resilience against this viral disease [14-17]. By enhancing our understanding of RTV epidemiology, host-pathogen interactions, and the socio-economic implications of disease outbreaks, we can devise integrated solutions that safeguard rice production and livelihoods for present and future generations.

Conclusion

In conclusion, the assessment of yield losses caused by Rice Tungro Virus (RTV) underscores the critical importance of understanding and managing viral diseases in rice cultivation. RTV continues to pose significant challenges to rice production, particularly in regions where the disease is endemic. Through this comprehensive review, we have examined the multifaceted aspects of RTV, including its epidemiology, symptomatology, transmission dynamics, and management strategies. The epidemiological complexity of RTV, involving interactions between the virus, insect vectors, and rice plants, underscores the need for integrated approaches to disease management. Efforts to develop RTV-resistant rice varieties have shown promise, but ongoing research is essential to enhance resistance durability and broaden the spectrum of resistance to different virus strains. Additionally, cultural practices, such as the use of resistant varieties, early planting, and vector control measures, play a pivotal role in reducing RTV incidence and mitigating yield losses. Emerging trends in RTV research, including advances in molecular genetics, bioinformatics, and ecological modeling, offer new avenues for understanding disease dynamics and developing innovative management strategies [18-20]. By fostering partnerships among stakeholders and leveraging emerging technologies and best practices, we can enhance our collective capacity to mitigate the impact of RTV and safeguard global rice production. In conclusion, this review serves as a timely contribution to the field of rice virology and agricultural science, providing insights and recommendations to guide future research, policy, and practice. By harnessing the collective expertise and innovation of the global community, we can work towards sustainable solutions that promote food security, livelihood resilience, and agricultural sustainability in the face of emerging challenges posed by RTV and other viral diseases.

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